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CeNano Research

Current projects (granted 2017)

In situ observations of nanoparticle precipitation during cooling in Inconel 718

Dunyong Deng (IEI, LiU), Kunpot Mopoung (IFM, LiU), Per Persson (IFM, LiU), Johan Moverare (IEI, LiU)

As a powder bed based additive manufacturing (AM) method, sometimes also referred to as 3D printing, electron beam melting (EBM) builds components in a layer-by-layer fashion. This is done at high vacuum and relatively high temperatures and has been widely applied to e.g. Nickel-based superalloys, such as Inconel 718 (IN718). IN718 has 5% of niobium (Nb) which contributes to strength from precipitation of γ’’- Ni3Nb phase. However, due to its poor diffusivity, Nb is prone to segregate to the interdendritic region during solidification and forms detrimental Laves - (Ni,Fe,Cr)2(Nb,Mo,Ti) phase. Our primary studies on EBM IN718 have confirmed the heterogeneous distribution of different phases and precipitates along the building direction, as shown in the Figure below, which is related to the varied thermal history that different locations experienced during processing. How to correlate this microstructural gradient in EBM material to the thermal history is an important prerequisite in order to understand the EBM process comprehensively. However, this is a topic that has not been addressed to a great extent in published literatures. Thus, the project is motivated to address the following questions:

1. What are the precipitates at different distances from the top surface?

2. Given that during the process, the base plate of the chamber is kept at 1000 °C, how long time does it take to dissolve the detrimental Laves phase and homogenize the microstructure? With the aid of In-situ TEM observation, mapping the evolution of certain elements distribution is possible, and would generate valuable thermodynamic data for development of a homogenization model for the EBM IN718 process.

3. During the in-situ annealing of Laves phase, would the release of Nb to the matrix lead to precipitation of δ phase? The aim is also to study how the γ’’ and γ’ phases precipitate during the cooling down stage after the EBM process? By applying different cooling schemes, the precipitation dynamics of γ’’ and γ’ will be monitored and compared.

In general, the knowledge from this study have a potential to improve EBM process, both in terms of processing speed and material quality and performance.

TEM bright field images showing the heterogeneous precipitates at different locations: (a) 10 µm, (b) 50 µm and (c) 1.5 cm from the top surface of EBM IN718 sample.

High performance light-emitting diodes based on nanometer-sized perovskite crystallites

Heyong Wang, Yong Yu, Mats Fahlman, Feng Gao (IFM, LiU)

Energy saving is one of the most important topics in recent years. The EU has set itself an energy efficiency target of >27% by 2030. Considering that displays and lighting in daily life accounts for a substantial proportion of energy consumption, efficient light-emitting devices (LEDs) will play an important role in reducing energy consumption. Recently, a new type of LEDs based on organometallic halide perovskites (PeLEDs) has been proposed. The figure below shows the crystal structure of 3D perovskites, which can be described by a chemical formula AMX3. The PeLEDs are solution processable and the emission color of perovskites can be tuned and hence constitute a new route towards low-cost and efficient displays and lighting. In this proposal, we aim to develop new ways to form uniform and ultra-flat perovskite films with nanometer-sized grains, allowing us to realize highly efficient PeLEDs. We will use additives in the 3D perovskite precursor solution to impede the growth of 3D perovskite grains and consequently decrease the grain size to < 10 nm. The reduced grain size would spatially confine electrons and holes and thus enhance bimolecular radiative recombination. Uniform perovskite films can also be anticipated based on these nanometer-sized grains, paving the way to realize high performance PeLEDs. We additionally will study the defects in the 2D/3D perovskite films, their nature and how they are influenced by growth conditions in order to optimize the films for use in PeLEDs, while also obtaining basic understanding of the film-forming process that can be used in other perovskite-based applications.

Polyhedral structure of perovskites

Experimental characterization and theoretical modelling of the antioxidant/catalytic properties of cerium oxide nanoparticles

Peter Eriksson, Alexey Tal, Weine Olovsson, Igor Abrikosov, Zhangjun Hu, Kajsa Uvdal (IFM , LiU)

In this project we are combining efforts from experimental characterization and theoretical modelling in order to achieve a better knowledge of the redox capability of cerium oxide nanoparticles (CeNPs). The redox capabilities have found to have high potential use in fuel cells, catalysis and also as antioxidant in biomedicine. However, the redox mechanism has not been fully understood. In last year’s Cenano-project, we successfully characterized the oxidation states of CeNPs by utilizing X-ray absorption near edge structures (XANES)-spectroscopy and verified the achieved XANES-spectra with theoretical ab initio modelling. This year we will experimentally and theoretically investigate the redox-reaction by using UV-VIS absorption spectroscopy, enabling real-time monitoring, and thereby be able to study dynamic oxidation state shifts of CeNPs.

Graphene-nanoparticle hybrid gas sensor

Marius Rodner, Rickard Gunnarsson, Ulf Helmersson, Jens Eriksson (IFM, LiU)

Two-dimensional materials, such as graphene, offer a unique platform for sensing where extremely high sensitivity is a priority, making them highly useful as gas sensors for detection of chemicals relevant to human health in the scope of air quality control. The Applied Sensor Science Unit at IFM has previously demonstrated that with the right amount of surface decoration with metal/oxide nanoparticles the surface chemistry can be modified to improve sensitivity, selectivity and speed of response toward, e.g., nitrogen dioxide (NO2) and toxic volatile organic compounds such as benzene and formaldehyde. The Plasma & Coatings Physics Division at IFM uses a newly invented technique that provides a new route to decorate materials with an expanded control of the decoration process with different nanomaterials. In this collaboration, we intend to place nanoparticles with different properties (size, composition, etc.) at selected positions on the epitaxial graphene on SiC substrates to investigate the change in sensitivity/selectivity towards different gases to ultimately use different assemblies for a sensor array. We aim to apply these approaches to graphene, the most sensitive transducer material in existence. The technology of epitaxial graphene on SiC, pioneered at LiU, will be leveraged to fabricate highly sensitive and reproducible sensor transducers on uniform monolayer graphene, a prerequisite for optimum sensitivity. Besides the evaluation of the produced chips as promising gas sensors also the surface is examined towards changes in morphology, e.g., using an atomic force microscope or Raman spectroscopy and Raman feature mapping before and after the decoration with nanoparticles.

Utilization of surface directed spinodal decomposition to design nanorod based opto-electronic devices

Elena Alexandra Serban, Fei Wang, Ferenc Tasnadi, Jens Birch, Ching-Lien Hsiao (IFM, LiU)

We will develop novel concepts in controlling the formation of superlattices (SLs) and core shell inside ternary III-nitride nanorods for optoelectronic devices, see Fig. 1. Our approach is to utilize the surface directed spinodal decomposition (SDSD) occurring in metastable InAlN nanostructures, see Fig. 2. A positive effects of the inherent phase instability of InAlN alloys is the facilitation of forming self-organized SLs in thin films and core-shell nanorod structures under specific growth conditions or post-heating treatment. We will understand the role of SDSD in the formation mechanism of InAlN SLs by (i) manipulating growth conditions, (ii) in-situ heating in scanning transmission electron microscope (STEM), and (iii) theoretical simulations.

In situ spectroscopic ellipsometry as a tool to study reductive surface chemistry in plasma CVD

Hama Nadhom, Andreas Jamnig, Kostas Sarakinos, Henrik Pedersen (IFM, LiU)

Metallic thin films play a crucial role as interconnects and barriers in nanoelectronics, where device miniaturization drives increasing demand for conformal film deposition on complex-shaped structures. Conformal film growth is facilitated by self-limiting chemical vapor deposition (CVD) techniques, which constitute a challenge for many of the first row transition metals as they are hard to reduce from ionic to metallic form. Newly started research at IFM seeks to understand the propensity of energetic electrons in pulsed plasmas to reduce metal centers in adsorbed molecules, and explore the viability of an altering adsorbing/reducing surface chemistry to enable self-limiting deposition of metal thin films. (Fig. 1) This CeNano project will study the dynamics of the adsorption of precursor molecules on the substrate surface, by in situ spectroscopic ellipsometry (SE) (Fig. 2). This is a first step towards understanding complex chemical interactions that result in the formation of metallic films using pulsed plasmas. Once the viability of this approach is established, SE can also serve as a tool to monitor the completeness of ligand removal in the plasma-on phase of the deposition cycle, which is crucial to minimize film contamination.

Theoretical characterization of point defects in silicon carbide and other materials

Joel Davidsson, Björn Lundqvist, Viktor Ivady, Rickard Armiento, Igor Abrikosov (IFM, LiU)

Effective engineering of materials defects and defect properties on the atomic (nano-) scale is crucial to create materials for applications in nanotechnology, i.e., ultra miniaturization of sensors, storage, processing, and communication. Silicon carbide (SiC) is a large bandgap semiconductor that have been in focus recently for its potential for applications in quantum information processing. It appears possible to engineer defects in SiC with optical and spin properties that are suitable as single photon sources, and states with long enough lifetime to act as qubit memory. We will generate defect supercells of impurities, interstitials, vacancies, and their complexes and do a systematic large-scale study using ab-initio calculations to enumerate a wide range of point defect properties, in particular, photoluminescence lines and thermodynamical stability. This will generate a dataset useful for identifying defects seen in experiments, explain their physics, and for finding out how to engineer defects with desired properties to target a range of possible nanotechnology applications. Our aim is to develop tools that allows us to extend the study to any material of interest.

Illustration of how generated supercells of C and Si vacancies in 4H-SiC are used to predict photoluminescence lines useful for identifying these defects. We will build a dataset for hundreds of defects in SiC and other materials.

Nanostructured single phase CaMnO3 thin films for thermoelectric applications

Erik Ekström, Johan Klarbring, Sergei Simak, Per Eklund (IFM, LiU)

Thermoelectric devices generate electricity from a temperature gradient across the device. In recent years, there has been a growing interest in oxide materials as thermoelectrics. While they are generally less efficient than conventional thermoelectric materials, their high chemical and thermal stability allow for their use in applications where other materials fail, for instance, in high temperature waste heat recovery where heat is converted to useful electricity.

In this project, we will study thin films of CaMnO3 which is one of the most promising n-type oxide thermoelectric materials. We will use a twinned theoretical/experimental approach to study the main factors influencing the thermoelectric efficiency of CaMnO3 thin films, namely phase stability, thermal conductivity and nanostructure formation.

Phase stability in CaMnO3: (Left) Phonon dispersion relation of CaMnO3 in the cubic perovskite phase showing two unstable phonon modes at the M and R points. (Middle) Illustration of the two unstable phonon modes which yields the orthorhombic perovskite-like ground state structure of CaMnO3 (right).

Characterization of Neutrophil Extracellular Traps (NETs) formation on iron oxide and titanium oxide nanoparticle based surfaces

Andreas Skallberg, Rickard Gunnarsson, Sebastian Ekeroth, Ulf Helmersson, Kajsa Uvdal (IFM, LiU)

Neutrophils are white blood cells and a predominant part of the innate immune system. They are short-lived compared to e.g. cells in tissue and they quickly respond to and become activated following a microbial threat. Neutrophils have the capacity to engulf microbes and release anti-microbials to kill invading pathogens. Neutrophils have lately shown to have an additional strategy to attack a possible threat, which is the release of extracellular fibers, primarily composed of granule proteins and chromatin, to form Neutrophil Extracellular Traps (NETs). The underlying mechanism of NET formation is not fully understood. Up until today only a few publications report on neutrophil responses upon nanoparticle treatment. NP parameters affecting the neutrophil behavior are indicated to be composition, size and shape. Neutrophils have several possible pathways leading to activation and it is not known if NPs of various composition triggers activation in the same manner. In the present project we will have the possibility to more precisely control the density of nanoparticles on a surface and correlate this to neutrophil responses such as NET formation. We now have the possibility to in detail study differences in neutrophil activation, signaling and characterizing NET formation on the nanoscale which may e.g. give important information on potential nanotoxicity.

Energy-filtered PEEM images of neutrophils deposited on iron oxide (a) and titanium oxide (b) nanostructured surfaces acquired at E-EF = 4.0 eV, showing NETs formation. Highlighted representation of NETs formation on iron oxide (c) and titanium oxide (d) nanostructured surfaces

Exploring surface functionalized MXene for spin/polarization-sensitive optoelectronic applications

Yuqing Huang, Quanzheng Tao, Johanna Rosen, Weimin Chen (IFM, LiU)

MXenes, a series of newly developed two-dimensional transition metal carbides, have attracted intense attention in many research fields ranging from energy storage to sensor applications. Recently, a 2D topological insulating (TI) phase has been predicted in MXene with the advantage of tunability by surface functionalization. Such “flexible” TI phase, once confirmed, would greatly benefit the TI research and could give rise to potential applications in spin/polarization-sensitive optoelectronics. Additionally, low dimensionality of the material can lead to breaking of local inversion symmetry, which is also critical for the generation of spin/polarization dependent photocurrent.

In this research program, we aim for fabrication and functionalization of monolayer MXene devices for spin/polarization sensitive optoelectronic applications, which will be tested by analyzing the polarization-dependent photocurrent as well as polarization resolved nonlinear optics. The program covers material synthesis/functionalization, micro device fabrication and characterization, as schematically illustrated in Fig. 1.

Fig.1 (a) Summary of our research program, and (b) a schematic illustration of a spin/polarization-sensitive optoelectronic device exploring the potential TI phase in MXene.

Previous projects (granted 2016)

Synthesis and characterization of chiral organic nanostructures

Lía Fernández del Río, Kenneth Järrendahl (IFM, LiU)

The PhD-project is dedicated to studies of natural systems using Mueller matrix ellipsometry (MMSE). The studies are based on the findings that many beetles in the superfamily Scarabaeoidea has cuticles with a chiral structure reflecting light with a high degree of circular polarization.
The main objectives have been
I) To understand the optical behaviour of the chiral nanostructures using MMSE.
II) To describe the structure behind these phenomena using optical and electron microscopy.
III) To mimic the nanostructures by synthesizing chitin structures and twisted III-nitride structures.
IV) To gain knowledge of the biological aspects of the optical phenomena.
Recent work include comparisons of the green and metallic-like parts of the cuticle for various Chrysina beetles. In the last phase of this PhD-project, emphasis will be on item II and IV. For IV we will develop a budding twinning work where Lía and PhD-student Jesper Fågelholm (supervised by Dominic Wright, IFM) will investigate feathers with similar green appearance as some beetles. Can the MMSE-data support the genetic studies of Red Junglefowl?

Images below are from the recent article: L. Fernández del Río, H. Arwin, K. Järrendahl, Polarizing properties and structure of the cuticle of scarab beetles from the Chrysina genus, Physical Review E 94 (2016) 012409 (DOI:http://dx.doi.org/10.1103/PhysRevE.94.012409)

Supramolecular coiled coil-based hybrid hydrogels for 3D cell culture of primary liver cells

Christopher Aronsson, Jonas Christoffersson, Daniel Aili, Carl-Fredrik Mandenius (IFM, LiU)

One of the major reasons for drug withdrawal during the pharmaceutical development process is hepatotoxicity. Many drug compounds are metabolized in the liver and even if the drug itself is not toxic the metabolite might be. To examine the effects of a new drug cell culture models are used before animal and human experiments to give a hint about the toxicity and efficacy of the compound. However, the complexity of organs is difficult to model in vitro. Standard cell culture models only provide a two dimensional (2D) surface for the cells which does not reflect how the cells are situated in vivo. Instead, the liver is built up by numerous liver lobules in the three dimensional (3D) space. The 3D orientation of liver cells has previously been shown to increase the expression of drug metabolizing enzymes, e.g. proteins belonging to the cytochrome P450 superfamily. This means that a 3D cell culture model could be of better use than 2D models during the pharmaceutical drug development process. Many different materials and methods for 3D cell culture have previously been reported, however, tuning the mechanical properties of the material for a specific cell type needs are often not possible in these systems. In this project, we will use a supramolecular coiled coil peptide-based hybrid hydrogel with tunable mechanical properties to study if primary liver cells shows an improved in vivo-like performance when grown in 3D compared to 2D. Furthermore, after optimization of the material to mimic the mechanical properties of the liver, drug toxicity studies will commence to compare this system with 2D systems.

Experimental characterization and theoretical modelling of the antioxidant/catalytic properties of cerium oxide nanoparticles

Peter Eriksson, Alexey Tal, Zhangjun Hu, Weine Olovsson, Igor Abrikosov, Kajsa Uvdal (IFM, LiU)

We are designing gadolinium-implemented cerium oxide nanoparticles (CeNPs) in order to combine  antioxidant capability and contrast enhancement for Magnetic Resonance Imaging. Our aim in this specific project  is  to investigate  the  surface catalytic process by studying the electronical structure  of  CeNPs   when swhitching between  the  3+ and 4+  oxidative states (Ce3+ and Ce4+),  and also  consider the influence of oxygen vacancies. The oxidation levels are studied using Near Edge  X-ray  Absorption Fine Structure  (NEXAFS)  on the  Ce M4,5 level and X-ray Photoelectron spectroscopy  (XPS) on Ce 3d electrons. Theoretically modelling (ab initio modeling) will be used as necessary aid for interpretation of measured NEXAFS and XPS spectra. Ab initio modeling for CeO2 (cerium oxide) has been developed for the bulk system, however nanoparticles significantly differ from their bulk configurations. The methodology of ab initio calculations of CeO2 must be revised and its applicability to nano-sized systems must be investigated.

Exploring 2D topological insulating phase in surface functionalized MXene for spin-sensitive optoelectronic applications

Yuqing Huang, Quanzheng Tao, Johanna Rosén, Weimin Chen (IFM, LiU)

Topological insulator (TI) has been discovered as unique phase of matter where combining effect of spin-orbit interaction and time-reversal symmetry lead to appearing of helical surface/edge state that give rise to exotic physics and promising spintronic applications. Recently, band topology has been theoretically investigated in a series of newly developed two-dimensional (2D) transition metal carbides, named MXene. Along the effort, 2D TI phase has been predicted in the material with great flexibility enabled by tunable surface functionalization and material diversity, which would greatly benefit the TI research.

In this proposed research program, we study the spin dependent process associated with the potential TI phase in various MXene that would lead to novel spin-sensitive optoelectronic applications. The program is developed with cooperation between material synthesis/optimization that lay the material foundation and device characterization that resolves the underlying spin physics. Our aim and program is illustrated with the figure below.

Brief summary of a) material synthesis and functionalization b) spin-sensitive optoelectronic device exploring the potential TI phase in MXene.

Single-phased and nanostructured thin CaMnO3 films for thermoelectric and fuel cell applications

Johan Klarbring, Erik Ekström, Sergei Simak, Per Eklund (IFM, LiU)

Thermoelectric materials generate electricity from a temperature difference across the sample. This can be used to convert waste heat into useful electricity. Thermoelectric devices are thus expected to help providing electricity, for which there is an ever growing demand in the modern society.  Good thermoelectric materials are good electric conductors that conduct heat poorly. A promising class of materials in this area is the perovskite-type oxides (see Figure). These materials, in addition to low thermal and high electronic conductivity, have high ionic conductivity and therefore could be promising not only as thermoelectrics but also as cathode materials in solid oxide fuel cells, which produce "green" electricity without polluting the environment. 

In this project, we will investigate the prospects of one such material, CaMnO3. We will synthesize thin CaMnO3 films using RF magnetron sputtering. The films will be characterized using a number of techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The thermoelectric properties will be measured and analyzed. The experiments will be complemented by, and compared to, quantum mechanical calculations based on the density functional theory (DFT).

The orthorhombic perovskite-like crystal structure of CaMnO3. Red, purple and light blue spheres represents O, Mn and Ca ions, respectively.

Self-limiting surface chemistry by in situ spectroscopic ellipsometry

Hama Nadhom, Viktor Elofsson, Kostas Sarakinos, Henrik Pedersen (IFM, LiU)

Metallic thin films play a crucial role as interconnects and barriers in nanoelectronics, where device miniaturization drives increasing demand for conformal film deposition on complex-shaped structures. Conformal film growth is facilitated by self-limiting chemical vapor deposition (CVD) techniques, which constitute a challenge for many of the first row transition metals as they are hard to reduce from ionic to metallic form. Newly started research at IFM seeks to understand the propensity of energetic electrons in pulsed plasmas to reduce metal centers in adsorbed molecules, and explore the viability of an altering adsorbing/reducing surface chemistry to enable self-limiting deposition of metal thin films. This CeNano project will study the dynamics of the adsorption of precursor molecules on the substrate surface, by in situ spectroscopic ellipsometry (SE). This is a first step towards understanding complex chemical interactions that result in the formation of metallic films using pulsed plasmas. Once the viability of this approach is established, SE can also serve as a tool to monitor the completeness of ligand removal in the plasma-on phase of the deposition cycle, which is crucial to minimize film contamination.  

Thermoplasmonic hydrogels for controlled cell adhesion and cell patterning

Ranjithkumar Ravichandran (IFM, LiU), Mina Shiran Chaharsoughi (ITN, LiU), Magnus Jonsson (ITN, LiU), Jaywant Phopase (IFM, LiU)

Temperature controlled detachment of cells from pNIPAM hydrogels are well known. This is a result of the temperature-mediated structural reorganisation of the pNIPAM polymers caused by the hydrophobic to hydrophilic transition, reducing cell adhesion. Possibilities to precisely modulate hydrogel temperatures locally may facilitate selective patterning of cells and enable fundamental studies of cell-surface interactions, cell mechanobiology, and cell migration. We propose to address this by incorporating plasmonic gold nanorods (AuNRs) in our newly developed bio-polymeric thermoresponsive hydrogel, which acts as local nanoscale heat generators when irradiated at their plasmon frequency. Our objective is to utilize the AuNRs to dynamically tune the properties of the thermoresponsive hydrogels and thus the cellular interactions with the material.

A) Calcein staining (left) showing the temperature dependent detachment of Human Skeletal Muscle Cells from our thermoresponsive collagen hydrogel (red arrows). The right panel shows a bright field (BF) image of the same area. B) Simulation showing the local character of plasmonic heating. The figure shows the temperature distribution around a gold nanorod heated to 50°C from a surrounding of 20°C. (Unpublished data)

Polymorphic self-organized multiple quantum wells in III-N nanorods

Mathias Forsberg, Alexandra Serban, Ching-Lien Hsiao, Galia Pozina (IFM, LiU)

Stacking faults forming periodic quantum wells (QW) have been observed in GaN nanorods grown by DC magnetron sputtering. This QW structures show in photoluminescence (PL) a significantly different polarization response compared to the GaN exciton transition. Using time-resolved μ-PL, we aim to study dynamic and polarization properties of excitons in the bare nanorods and in the hybrid samples covered with polyfluorene. Expecting non-radiative resonant energy transfer (NRET) due to the Förster interaction between QW excitons and polyfluorene film together with polarization properties of emission could be of high importance for nano-photonic applications.

Snapshot on cell response on nanoparticles as a function of size, shape and surface density to capture the moment of initial immune response

Andreas Skallberg, Rickard Gunnarsson, Sebastian Ekeroth, Ulf Helmersson, Kajsa Uvdal (IFM, LiU)

Metallic nanoparticles have been widely studied and nanoparticulate-based applications are today available in areas such as medicine, energy and electronics. Nanoparticles in medical applications are very promising when scaling down the material i.e. due to enhanced surface to volume ratio, penetration ability of tissues and cells and capability for targeted drug delivery. Neutrophil granulocytes are inflammatory cells capable of inducing a strong immune response once they encounter a foreign object, e.g. as prepared non-coated nanoparticle. However, the cellular response is shown to be dependent upon several features of the nanoparticle, such as size, shape and surface density. In this project we will investigate cell response on nanoparticles as a function of size, shape and surface density of nanometer scaled structures of titanium oxide and iron oxide and capture the moment of initial immune response, among others. Taken together these experiments will show if and how shape, size and surface density of these nanometer scaled structures of titanium oxide and iron oxide modulate neutrophil cell response. Finally, surface functionalization of the nanoparticles followed by cell exposure will be investigated with NanoESCA. To our knowledge, no previous studies have evaluated cellular responses using NanoESCA.

(Left) Photo emitted electron microscopy image showing neutrophil deposit on a silicon surface. (Upper right) Schematic picture of as prepared titanium oxide nanoparticles prepared by plasma as a function of size. (Lower right) SEM images of increasing size and shape of nanometer scale structures of titanium oxide.

Theoretical study and attempt of synthesis of boron subnitride and boron subcarbonitride

Laurent Souqui, Annop Ektarawong, Björn Alling, Anne Henry (IFM, LiU)

Boron subnitride and boron subcarbonitride belong to the family of icosahedral boron-rich solids, exhibiting several outstanding properties, e.g. high hardness, high melting point, chemical inertness and low density, and thus being promising materials for a wide range of technological applications. Generally, high-temperature high-pressure techniques are used for synthesizing the subnitride [1, 2]. Theses methods, somehow, have a relatively low yield, thus limiting not only its utilization but also accessibility to the material’s properties. Consequently, several issues about the subnitride, e.g. crystal structure, stoichiometry, stability and properties, have not yet been unanimous among the community. The subcarbonitride, on the other hand, has been recently predicted and proposed to be
a new stable phase of icosahedral boron-rich solids [3], where its synthesis has never been reported in any experiment. In this project, the thermodynamic stabilities as a function of pressure and temperature, as well as the properties of these materials will be investigated, using first-principles calculations, which will then be served as a guideline for exploring possible routes for syntheses of the subnitride and subcarbonitride thin films, using chemical vapor deposition. The structures and properties of the as-synthesized films will then be characterized by X-ray diffraction technique, Xray photoelectron spectroscopy, and IR spectroscopy, and compared with the results, obtained from the calculations.

References
[1] H. Hubert, J. Solid State Chem. 133, 356 (1998).
[2] O. O. Kurakevych et al., Acta Cryst. C63, i80 (2007).
[3] H. Zhang et al., Phys. Rev. B. 93, 144107 (2016).

3-dimensional icosahedral network of boron subnitride and boron subcarbonitride on the nano-scale (left figure), built up of B12 icosahedra (white spheres) and inter-icosahedral chains (brown spheres), as a building block (right figure). The inter-icosahedral chains can either be N-B-N or N-V-N (V = vacancy) for boron subnitride, and are N-B-C and C-B-N for boron subcarbonitride, as proposed in Ref. [3].

Interfacial coherency and strength in nanostructured nitrides

Fei Wang, Kumar Yalamanchili, Naureen Ghafoor, Ferenc Tasnadi (IFM, LiU)

We tailor explore the interfacial physics of different transition metal nitride superlattices. Beyond the thermodynamic stability we characterize their response (deformation) to external force. Our novel concept is that finding the right interface orientation between the parent materials results in enhanced stability and improved strength, such as matching the LEGO bricks. The combination of different binary nitrides (TiN, TaN, ZrN, HfN, AlN, ScN, etc.) means different interfacial chemistry through the different interfacial orientations what can be tested by micropillar compression.

With ab-initio simulations we explore the interfacial chemistry in different transition nitride multilayers, see Figure. Beyond the perfect interfaces we aim to investigate the effect of vacancies and the presence Oxygen at the interface. The experimental task is that by tuning the growth parameters we alter the interface structure to the theoretically predicted stable interfaces and then we apply external force to test the deformation and the strength of the nanocomposite, see Figure.

Three interfaces between cubic and wurtize phases which are grown in ZrAlN/TiN multilayers and deformation is performed using micropillar compression to compare the fracture resistance.

High resolution graphene based gas/liquid sensor platform

Valdas Jokubavicius, Manuel Bastuck, Mike Andersson, G. Reza Yazdi (IFM, LiU)

This project aims to fabricate a sensor platform for indoor air quality monitoring. The combination of surface engineering of SiC on the micro- and nano-scales through well-defined etching with the procedures for epitaxial processing of graphene on SiC make the fabrication of gas/liquid sensors with tunable properties possible. Graphene, a single layer of carbon atoms arranged in a honeycomb lattice, is highly sensitive to changes in its chemical environment due to its extremely high electron mobility at room temperature, its maximized surface area per unit volume and the electron transport through graphene thus highly sensitive to adsorbed molecular species, as well as its low electrical noise (due to the quality of its crystal lattice and its very high electrical conductivity).

The SiC surface quality is crucial for growth of graphene. Commercial, mechanically polished SiC wafers are often damaged and show a high density of scratches when studied by AFM (Fig. 1a). Here thermal etching will be used prior to the epitaxial growth of graphene to improve the surface quality of the SiC substrates (Fig 1b). Growth of epitaxial graphene with different thickness will be performed after etching (Fig.1c). For device fabrication (Fig. 2a and b), a suspended gate and electrical contacts to the drain, source, and gate terminals will be processed on the SiC/graphene substrate and characterized electrically (Fig. 2c). Then the effect of graphene thickness and bias conditions on the sensitivity to different pollutant gaseous substances will be studied to establish basic principles for the transducer mechanism. The final aim is the optimization of device layout, layer thicknesses, materials and operation in order to develop a sensor platform for indoor air quality monitoring.   

Fig. 1 AFM images of SiC surface a) before thermal etching, b) after etching, c) with graphene layers
Fig. 2 displays in (a) the interaction of substances interesting to measure with the graphene layer, which at the same time acts as the channel in a suspended gate (SG) FET device, the electrical characteristics of which depends on the applied suspended gate bias (VGS) and gas adsorption, thereby facilitating tuning of the device for optimum sensitivity

Correlating performance of organic solar cells with nanostructures of active layer via studying the cross-sections of devices with SEM

Deping Qian (IFM, LiU), Pimin Zhang (IEI, LiU), Ru Peng (IEI, LiU), Fengling Zhang (IFM, LiU)

Percolating network of two materials in the active layers determines charge generation and transport in solution processed bulk-heterojunction organic solar cells. Imagining the nanostructure of cross-sections of the active layers with Scanning Electron Microscopy (SEM) will directly provide information on vertical distribution of two materials. However, it is challenge to prepare smooth cross-sections of organic materials on hard/flexible substrates and get clear SEM images with layer thickness only ~100 nm. The high resolution SEM at IEI is capable of imaging very fine microstructural features. With this proposal, we will initiate an interdisciplinary synergetic collaboration between IFM and IEI to better control the device performance and reproducibility (important for industrialization of organic solar cells) as well as lead to a long term collaboration between two departments.

Schematic diagram of a flexible semitransparent OPV. The green layer is an active layer consist of two materials for exciton dissociation. SEM image shows the percolation of two materials.

Previous projects (granted 2015)

The missing link between theory and experiment for the understanding of the nanostructure of amorphous boron carbide - the final steps (continuation)

Annop Ektarawong, Mewlude Imam, Henrik Pedersen, Björn Alling (IFM, LiU)

Boron carbide thin films are the material of choice for a new generation of neutron detectors at the European Spallation Source (ESS) in Lund. When grown with physical and vapour deposition techniques amorphous B4C is obtained. The atomic and nanoscale structure of these coatings determine their mechanical, electrical, and chemical properties, but are currently unknown. In this project these amorphous materials are investigated with combined theoretical and experimental methods. On the theoretical side we will use quantum molecular dynamics meltquench and structure prediction methods to obtain candidate amorphous structure models including radial distribution functions, average coordination numbers and boron-carbon configuration preferences. These will then be compared with the structural information of our films using pair distribution function analysis of synchrotron X-ray total scattering, nuclear magnetic resonance, and neutron scattering techniques.

[1] A. Ektarawong, S. I. Simak, L. Hultman, J. Birch, and B. Alling PRB 90, 024204 (2014)

The nanoscale of disordered B4C possibly built up of sub-nanometer sized B11C icosahedra and C-B-C linear chains. From ref [1].

Biocompatibility studies of engineered nanoparticles aimed for use in biomedical applications (continuation)

Natalia Abrikossova, Caroline Brommesson (IFM, LiU)

The demands on all nanomaterials aimed to be used in biological applications are extensive. Main focus in this project is to evaluate mechanisms of interaction between gadolinium oxide nanoparticles (Gd2O3) and inflammatory cells (in vitro). Gd2O3 nanoparticles are, due to their absorption and magnetic properties, promising for contrast enhancement during examinations with the clinically important diagnostic techniques computed tomography (CT) and magnetic resonance imaging (MRI). We use human isolated blood cells i.e. neutrophil granulocytes, platelets and monocytes as these are rapidly responding cells and also among the cells that will be the first to encounter intravenously administered nanoparticles. We evaluate cellular uptake of nanoparticles as well as functional responses following exposure to nanoparticles, e.g. cell aggregation and production of reaction oxygen species. Increased knowledge of the involved pathways and uptake mechanisms will be helpful in the future design of biocompatible nanoparticles.

Uptake of Gd2O3 nanoparticles in neutrophil granulocytes

Polarizing properties and structural characteristics in the cuticle of the scarab beetle Chrysina gloriosa (continuation)

Lía Fernández del Río, Hans Arwin, Kenneth Järrendahl (IFM, LiU)

The scarab beetle Chrysina gloriosa has an eye catching metallic coloration originating from the reflection of light on the exocuticle. The reflected light is elliptically polarized and in some cases even circularly polarized. In this project the chiral exocuticle structure and its optical properties will be studied with SEM, TEM, AFM and Mueller-matrix ellipsometry and also optically modelled. Other scarab beetles with similar optical features will also be studied. The objective is to serve as inspiration in the production of bio-inspired materials which would have metallic appearance, tunable optical properties and organic composition.

Left: Scarab beetle Chrysina gloriosa. Right: TEM image showing a cross-section of the green area of C. gloriosa

Developing self-powered wireless piezoelectric systems based on ZnO nanowires (new)

Eiman S. Nour, Hatim Alnoor, Andrejs Bondarevs, Shaofang Gong, Omer Nur (ITN, LiU)

Zinc oxide (ZnO) as a semiconductor and piezoelectric material having also many other interesting chemical and physical properties is under focus for some time. Its wide bandgap and deep level defects are of interest for many photonic devices. In addition, ZnO is bio-safe, biocompatible, and possesses relatively high electromechanical coupling coefficient. The later property also makes ZnO a strong piezoelectric material. In addition, ZnO possesses self-organized growth, a fact that makes it possible to synthesize it on any substrate using simple chemical approaches, like e.g. the aqueous chemical growth. Recently we have demonstrated an anisotropic direction sensor with self-power capability as it harvests the mechanical energy that caused the deflection. The sensor was based on ZnO nanowires (NWs) grown on both sides of a large plastic substrate [1]. Now we are extending the self-powered sensor concept to act also as a wireless device. This work is performed in close collaboration with Prof. Shaofang Gong and his group. Such self-powered wireless sensors can be useful for surveillance and security systems.

[1] E. Nour, Chan Oeurn Chey, M. Willander and O. Nur,’’ A flexible anisotropic self-powered piezoelectric direction sensor based on double sided ZnO nanowires configuration‘’ Nanotechnology (2015).

Organic/inorganic hybrid structures fabricated utilizing III-N nanorods (continuation)

Mathias Forsberg, Galia Pozina (IFM, LiU)

Hybrid structures based on III-N semiconductor nanostructures and organic polymers can be designed to utilize non-radiative resonant energy transfer (NRET) from excitations generated in the energy donor material to the excitation in the organic film playing a role of the energy acceptor. Such hybrids have potential applications as highly efficient emitters for down converting of UV and blue light to visible. In the project we study a new hybrid nanostructures based on organic polyfluorenes with emission in the green region and GaN nanorods grown by DC magnetron sputtering.

Versatile water-dispersible ultrabright semiconducting polymer dots (Pdots) as platform for biomedical ratiometric fluorescent sensing (new)

Peter Eriksson, Zhangjun Hu (IFM, LiU)

This project aims to develop water-dispersible Pdots for ratiometric fluorescent sensing. Specific fluorescent probes are strategized and conjugated onto the polymeric scaffolds to achieve sensor-functionalized polymers. By following the intraparticle Förster resonance energy transfer (FRET) mechanism, FRET-based ratiometric probes can be easily generalized by assembling thus functionalized polymers (act as FRET acceptor) with a semiconducting polymer (donor) through hydrophobic interactions. Our main interest is to utilize the water-dispersiblility and easy-integration of Pdots platform to explore new ratiometric probes and evaluate them for quantitative bio-analysis.

Simulation and modeling of nanoscaled porous membranes and electrodes (new)

Anton Volkov, Xavier Crispin, Igor Zozoulenko (ITN, LiU)

Porous membranes and electrodes play a central role in a variety of devices including
supercapacitors, fuel cells, batteries and other electro-chemical devices.1 The large surface area inside a porous electrode greatly enhances charge storage capabilities as well as the magnitude of current in such structures in comparison to conventional devices with planar electrodes. Over the last 20 years, the blossoming field of Organic Electronics has opened new horizons to fabricate nanoporous structure and devices based on low-cost, printable flexible organic materials such as organic polymers. An experimental research addressing nanoporous supercapacitors and organic nanostructures based on conducting polymers, in particularly, on PEDOT, is currently performed at the Laboratory of Organic Electronics under the supervision of Prof. Xavier Crispin. Unfortunately, despite achieved experimental progress, the related theory is not developed yet and the fundamental knowledge on the temporal dynamics of porous electrode charging and charge storage on a nanoscaled level remains to a large extend missing. The absence of the corresponding theoretical foundation leads to an incomplete understanding of the experimental results and hinders further development of the devices utilizing nanoscaled porous electrodes. Thus, the main aim of the present project will be to develop simulation and modeling tools in order to understand the physical process in the systems at hand and to provide guidelines for the material and device design and rationalize experimental measurements. A close interaction between the theory and experiment would therefore result in a significant synergy effect.

Nanoscaled porous PEDOT matrix embedded in electrolyte/gel

Previous projects (granted 2014)

Sum decomposition of Mueller matrices of biological nanostructures

Roger Magnusson, Kenneth Järrendahl, Hans Arwin (IFM, LiU)

A Muller matrix M provides a full description of the specular reflection properties of a surface and includes irradiance reflectance, polarization and depolarization properties. Experimental M are obtained by spectroscopic ellipsometry. Here the objective is to sum decompose a depolarizing Muller matrix according to

𝐌=𝜆1𝐌1+𝜆2𝐌2+𝜆3𝐌3+𝜆4𝐌4 Σ𝜆𝑖=1

where Mi are non-depolarizing matrices with relative weights λi. For a non-depolarizing reflector only one of the four terms is non-zero whereas for a depolarizing M two or more terms are non-zero. An eigenvector analysis of the covariance matrix of M, gives a hint to the appropriate set of matrices Mi to use and the λI’s, are eigenvalues of the covariance matrix. Once the set of Mi is found, a regression decomposition (e.g. in MATLAB) can be performed. As an example, a decomposition of M measured on the beetle Cetonia aurata is shown below. Only two eigenvalues are non-zero and a possible decomposition is as a mirror and a left-handed circular polarizer. The last two terms do not contribute as λ3 and λ4 are zero, but would correspond to a left-handed circular polarizer and a halfwave plate for more complex reflectors.

Once the decomposition strategies are settled, a classification scheme can be established. One strategy is to introduce four major classes of reflectors corresponding to the number of non-zero λi. The spectral and angular dependence should then be condensed to a single parameter, e.g. by averaging each λi over the visible spectrum, or by defining other measures which uniquely describe the reflector. For colors we have color systems like the RGB, L*a*b*, etc. The ultimate goal in this project is to find a corresponding system with polarization coordinates describing a reflector.

Interface coherency studies in c-Ti1-xCrxN/h-AlN and c-Ti1-xZrxN/h-AlN (x=0-1) multilayers

Siva Phani Kumar Yalamanchili, Fei Wang, Naureen Ghafoor, Ferenc Tasnádi (IFM, LiU)

Our aim is to revisit the long existing concept of favorable isostructural decomposition in TiAlN hard coatings and reveals a novel research route for hard multicomponent nanostructured materials. Recent high resolution structural investigation on atomistic scale indicates, that formation of hexagonal AlN is not necessarily detrimental for mechanical properties as long as interface coherence upholds (see Fig.). We study coherent cubic to hexagonal interface in hard coating multilayers, such as c-Ti1-xMxN/h-AlN (M:Cr, Zr, x=0-1). Our major interest is to prove the novel concept by energetic arguments, explore the impact of interface composition on the thermodynamic properties (stability) and also to utilize the knowledge for developing new hard coatings.

Eu-doped Gd2O3 nanoparticles for specific dual-modal biomedical imaging

Andreas Skallberg, Zhangjun Hu (IFM, LiU)

This project has been aimed to design and synthesize the ligands, which contain exceptional chelate sites (for grafting the surface of Eu-doped GO NPs), screened water-soluble moieties (for stabilizing NPs and enhancing biocompatibility); conjugated aromatic parts (for sensitizing Eu luminescence via antenna effects) and pre-reserved reactive sites (for further decorating with the targeting molecules). This final aim is to optimize the preparation and modification of the titled NPs by using the synthesized ligands; and evaluate the property aspects and targeting imaging capacities of NPs. We will evaluate the probe performance as both preparative MRI and intraoperative tumor paint for optical tumor delineation.

Surface diffusion studies of non-carbide forming adatoms on graphene surfaces

Chamseddine Bouhafs, Linda Karlsson, Vanya Darakchieva, Per Persson (IFM, LiU)

This project will investigate the kinetics and interactions of non-carbide forming metal adatoms on the surface of the 2D material graphene. The purpose is to address original and significant surface physics, to determine metal-graphene interfaces and explore binary phase diagrams of two-dimensional structures.

Use and functionalization of graphene for electronic devices requires the successful attachment of metal atoms and contacts to the graphene sheets. Growth of thin metal sheets onto graphene films have however not been investigated in detail, but rather in macroscopic perspectives, neglecting the atomic arrangement at the interface and the consequence on e.g. charge transfer and electronic states the arrangement may have.

Hence, the aim of this project is to deposit a sub monolayer of select elements (non-carbide forming) on graphene, and to investigate the behavior of the adatoms as they migrate in-situ. The assembly will be heated, also in-situ, using a high temperature annealing holder inside the electron microscope, and the progress, kinetics and ripening details will be monitored live.

At LiU, the Electron Microscopy of Materials are advancing low-kV methods for imaging of structures at atomic resolution, e.g. by annular bright field scanning TEM and by improved aberration corrected imaging at low-kV. The former is a new technique which we have implemented to visualize both heavy and light elements simultaneously. Together, these methods constitute the key elements for a successful outcome.

Two figures of MXene (another 2D material) on which we can determine the movement and coalescence of Ti adatoms on the MXene surface.

Developing a smart electronic paper based on piezoelectric nanowires

Eiman S. Nour, Hatim Alnoor, Mats O. Sandberg*, Omer Nour (ITN, LiU)    (*also at Acreo AB)

Zinc oxide (ZnO) is a semiconductor possessing a strong piezoelectric effect and is characterized by many other interesting chemical and physical properties. ZnO also possesses self-organized growth, a fact that makes it possible to synthesize it on any substrate, even those of amorphous nature, like e.g. paper. In addition, its nanostructures which can be synthesized by low temperature methods (˂100 oC) constitute one of the richest families of nano-morphologies. In this project we utilize the piezoelectric properties of ZnO nanowires synthesized on paper substrate to develop a ‘’smart electronic’’ paper which harvest mechanical energy provide by writing pressure to electrical signals. The concept can be of potential for many applications, like signature verification, mobile electronic keyboard etc.. So far the preliminary results are encouraging and we have obtained an open circuit harvested voltage of up to 4.8 V.

Registration of nanoparticle-microelectrode collisions: electroanalysis for nanomaterials characterization and environmental monitoring

Alina Sekretaryova, Onur Parlak, Mikhail Vagin, Martin Mak (IFM, LiU)

The extensive industrial usage the nanoparticles (NP) leads to their release into the environment with yearly exponential increase due to use intensification(1). In particular, Silver NP are in extensive use in variety of products due to their biocide activities(2) and are perhaps the most worrying of industrially-manufactured NP because of inherent toxicity to mammalians(3) and aquatic life(4), while these commercial products are a major and growing source of silver NP to the environment(5, 6). However, the behavior of NP in the environment as well as in the sewage treatment and waste incineration plants is largely unknown due to the lack of experimental data of the NP environmental detection. Appeared recently(7, 8), direct electrochemical detection of nanoparticles by means of the registration of their single collisions with microelectrode surface represents one of the most advanced techniques of NP real-time quantification and characterization(9, 10). The main objective of the Project is the development of new platform for NP characterization, to generate new knowledge in electrochemical behavior of NP and to explore the potential application of NP. The main goals are NP quantification and characterization with collision detection for water quality monitoring. The Project will promote the synergetic research interactions based on ongoing PhD Projects between A. Sekretaryova (supervisor: Dr. M. Vagin) working on electrochemical environmental monitoring and O. Parlak (supervisor: Dr. M. Mak) working on NP fabrication.

1. J. Fabrega et al., Environ.Int., 2011, 37, 517; 2. H. Lara et al., J.Nanobiotechnol., 2011, 9; 3. M. Ahamed et al., Clin.Chim.Acta, 2010, 411, 1841; 4. A. Hinther et al., Environ.Sci.Technol, 2010, 44, 1841; 5. M. Eckelman et al., Environ.Sci.Technol, 2007, 41, 6283; 6. Y. Ju-Nam et al., Sci.TotalEnviron., 2008, 400, 396; 7. M. Heyrovsky et al., Langmuir, 1995, 11, 4293; 8. X. Y. Xiao et al., JACS, 2007, 129, 9610; 9. E. Stuart et al., Nanoscale, 2013, 5, 174; 10. Y. Zhou et al., Angew.Chem.Int.Ed., 2011, 50, 4219.

The missing link between theory and experiment for the understanding of the nanostructure of amorphous boron carbide

Annop Ektarawong, Mewlude Imam, Henrik Pedersen, Björn Alling (IFM, LiU)

Boron carbide thin films are the material of choice for a new generation of neutron detectors at the European Spallation Source (ESS) in Lund. When grown with physical and vapour deposition techniques amorphous B4C is obtained. The atomic and nanoscale structure of these coatings determine their mechanical, electrical, and chemical properties, but are currently unknown. In this project these amorphous materials are investigated with combined theoretical and experimental methods. On the theoretical side we will use quantum molecular dynamics meltquench and structure prediction methods to obtain candidate amorphous structure models including radial distribution functions, average coordination numbers and boron-carbon configuration preferences. These will then be compared with the structural information of our films using pair distribution function analysis of synchrotron X-ray total scattering, nuclear magnetic resonance, and neutron scattering techniques.

[1] A. Ektarawong, S. I. Simak, L. Hultman, J. Birch, and B. Alling PRB 90, 024204 (2014)

The nanoscale of disordered B4C possibly built up of sub-nanometer sized B11C icosahedra and C-B-C linear chains. From ref [1].

Nanomechanical and nanodynamic properties of protein entities participating in dynamic conformational selection and multimodular recognition

Madhanagopal Anandapadamanaban, Maria Sunnerhagen (IFM, LiU)

From an engineering point of view, proteins are mechanical devises engineered to perform various tasks in the nano-dimensional range. Protein α-helices, the ’pistons’ of action, range from 1-50 nm in length and hundreds of nm when bundled, and protein β-sheets, which can be wrapped to form shapes of up to 100 nm and more, together form the structural framework where nanobiological functionality is encoded. Disordered regions have recently been recognized to function both as multirecognition elements in protein ’hubs’ and as flexible linkers organizing modular entities into multifunctional units. We are studying the structural and dynamic properties of proteins using both crystallography and NMR, together with other biophysical techniques such as CD, ITC, fluorescence and SPR, and apply this both to proteins involved in transcriptional activation (see our TBP-TAF1 complex in figure), but also in an ongoing study on the E3 ubiquitin ligase TRIM21 involved in autoimmune disease.

Electrostatic surface representation of yTBP, with the bound yTAF1 transcriptional regulator in green and with its TBP-anchoring residues annotated.

Biocompatibility studies of engineered nanoparticles aimed for use in biomedical applications

Natalia Abrikossova, Caroline Brommesson (IFM, LiU)

The demands on all nanomaterials aimed to be used in biological applications are extensive. Main focus in this project is to evaluate mechanisms of interaction between gadolinium oxide nanoparticles (Gd2O3) and inflammatory cells (in vitro). Gd2O3 nanoparticles are, due to their absorption and magnetic properties, promising for contrast enhancement during examinations with the clinically important diagnostic techniques computed tomography (CT) and magnetic resonance imaging (MRI). We use human isolated blood cells i.e. neutrophil granulocytes, platelets and monocytes as these are rapidly responding cells and also among the cells that will be the first to encounter intravenously administered nanoparticles. We evaluate cellular uptake of nanoparticles as well as functional responses following exposure to nanoparticles, e.g. cell aggregation and production of reaction oxygen species. Increased knowledge of the involved pathways and uptake mechanisms will be helpful in the future design of biocompatible nanoparticles.

Uptake of Gd2O3 nanoparticles in neutrophil granulocytes

Imaging strategies for dynamic and responsive supramolecular nanostructures by applying low-kV and in-situ transmission electron microscopy

Ingemar Persson, Camilla Sandén, Per Persson, Daniel Aili  (IFM, LiU)

In this project we will investigate possible nondestructive routes for imaging of supramolecular assemblies and their response to external stimuli by applying electrons, accelerated at low voltages (60 kV) in the transmission electron microscope. Specifically, the intentions are to visualize molecules, supramolecular assemblies (peptides and lipid nanostructures) and gold nanoparticle hybrids and find methods to for low dose imaging where functionality and structure of molecular species are retained. Imaging will be carried out using the monochromated and double corrected Titan^3 microscope at LiU.

Investigating magnetron sputter epitaxy of ZrB2 on MOCVD grown GaN epi-layers for potential use in High Electron Mobility Transistors

Lina Tengdelius, Xun Li, Hans Högberg, Urban Forsberg (IFM, LiU)

ZrB2 is a refractory and conductive ceramic with high temperature stability and with potential use as a heat shield material for space vehicles. As thin film material the phase exhibits a good lattice match to GaN(0001)   and 4H-SiC(0001) and has a 6:5 “magic” mismatch to Si(111). Recently, we demonstrated for the first time that epitaxial ZrB2 films can be sputtered from a compound target on 4H-SiC(0001) and Si(111) substrates (L. Tengdelius et al., physica status solidi A,211, 636-640 (2014)). However, epitaxial growth on GaN(0001) remains to be demonstrated as apparent from the selected area diffraction pattern in figure 1. For progress in the field, the project will grow and evaluate different templates, AlN, AlGaN and GaN on SiC substrates, see inset in figure 1. Previous investigations of sputtered ZrB2 on GaN have shown that the surface condition of the GaN template is of high importance, see interface between the substrate and the polycrystalline ZrB2 film in figure 1. Therefore, different surface pretreatment of the templates will be performed; both chemical cleaning as well as in situ hydrogen etching at an elevated temperature will be investigated.

Organic/inorganic hybrid structures fabricated utilizing III-N nanorods

Mathias Forsberg, Galia Pozina (IFM, LiU)

Hybrid structures based on III-N semiconductor quantum well (QW) and organic polymers utilizing non-radiative resonant energy transfer (NRET) from excitations generated in QW to excitons in the fluorescent layer have potential applications as efficient emitters for down converting of UV and blue light. In this project a new design of hybrid will be used: organic polyfluorenes with emission in visible region deposited on heterostructured AlInN/GaN nanorods produced by DC magnetron sputtering.

Designed nanoparticles for graphene-based gas sensors

Rickard Gunnarsson, Jens Eriksson, Ulf Helmersson (IFM, LiU)

Graphene based gas sensors have a high sensitivity and are therefore a promising platform for detecting toxic vilotile organic compounds. However, these sensors lack selectivity and suffer from poor response and recovery time. The aim of this project is to coat graphene sensors with nanoparticles to circumvent these issues. The nanoparticles will be synthesized with a novel plasma based process, that allows for size and stoichiometry control of metal oxide nanoparticles. It is also possible to coat the nanoparticles with another metal which allows for a wider selection of material combinations to be used.

Boron Nitride – the ultimate substrate for graphene

Mihails Cubarovs, Anne Henry (IFM, LiU)

A chemical vapor deposition process has been developed for the growth of sp2 boron nitride (sp2-BN) on sapphire (Al2O3) with the need of an AlN buffer layer. We have shown that H2 should be used as carrier gas and the addition of small amount of Si in the gas mixture favors the growth of high quality rhombohedral layer. The epilayer surface is observed with nanosize features and when manipulating the material an exfoliation appears easy.

Polarizing properties and structural characteristics in the cuticle of the scarab beetle Chrysina gloriosa

Lia Fernandez del Rio, Hans Arwin, Kenneth Järrendahl (IFM, LiU)

The scarab beetle Chrysina gloriosa has an eye catching metallic colouration originating from the refection of light on the exocuticle. The refected light is elliptically polarized and in some cases even circularly polarized. In this project the chiral exocuticle structure and its optical properties will be studied with SEM and Mueller-matrix ellipsometry and also optically modelled. Other scarab beetles with similar optical features will also be studied. The objective is to serve as inspiration in the production of bioinspired materials which would have metallic appearance, tunable optical properties and organic composition.

Tailoring the light emission efficiency of ZnO nanoparticles via polymer coating for optoelectronic applications

Martin Eriksson, Deping Qian, Volodymyr Khranovskyy, Fengling Zhang, Fredrik Karlsson (IFM, LiU)

ZnO is a semiconductor material with outstanding light emission properties. Due to its direct band gap and high exciton binding energy, it enables efficient UV light emission (λ ~375 nm) up to room temperature. However, the available surface states trap charge careers, which reduces the radiative recombination rate of the material. This is especially noticeable for nanoparticles, which have large surface-to-volume ratios. The aim of this study is to improve the light emission efficiency of ZnO nanoparticles by coating them with polymer. In this project we will investigate the light emission features of ZnO nanoparticles by microphotoluminescence spectroscopy and reveal how it can be influenced via coating by polymers. We plan to study both the time integrated and the time dependent photoluminescence of the ZnO nanoparticles coated by different polymers, such as PEO and PMMA, in comparison to bare ZnO nanoparticles. As a long term perspective, this study aims to contribute to applications such as inorganic nanoparticle/organic polymer based light emitting diodes (InOr-LEDs).

Low temperature time resolved photoluminescence spectra of ZnO nanoparticles.

Ultrabright semiconducting polymer dots (Pdots) for specific cancer cell targeting

Peter Eriksson, Xuanjun Zhang (IFM, LiU)

Semiconducting polymer nanoparticles (Pdots) are a new class of fluorescent nanoprobe with superior characteristics such as low toxicity, ultra bright photoluminescence, nonblinking, and fast emission rates. We are now developing reliable methods to (1) functionalize the Pdot surface for specific bioconjugation with biomolecules such as proteins, cancer drugs, antibodies, etc; (2) tune emission to Near-Infrared (NIR) region for practical in vivo applications. The bright NIR fluorescent Pdots with specific targeting ligands are very promising for a variety of biological applications.

Previous projects - highlights 2011

Self-assembly of Anisotropic Nanostructure for Metal Enhanced Fluorescence and Plasmonically Triggered Drug Release

Daniel Aili, Erik Martinsson (IFM, LiU)
Mira Patel, Atul Parikh (UC Davis, USA)
Self-assembly is a powerful strategy for obtaining complex nanostructures and hybrid materials. Structurally well-defined anisotropic supramolecular nanostructures are frequently found in nature but are, however, inherently difficult to realize synthetically using techniques based on molecular self-assembly. In this project, a novel strategy will be examined for obtaining anisotropic assemblies of plasmonic NPs using a biomimetic supramolecular template based on reconstituted Lipoprotein A (LpA).

Exploring ZnO nanostructures embedded in polymers for enhanced performance in light emission and photovoltaic applications

Fengling Zhang, Fredrick Karlsson (IFM, LiU)

ZnO is a material with excellent optical qualities, with a potential to replace the significantly more expensive GaN for white and blue light-emitting diodes (LEDs). However, currently the main challenge for ZnO-based LEDs is the inherent difficulty to p-dope ZnO. A promising bypass of this problem is to grow high-quality ZnO nanostructures on p-doped foreign substrates, such as Si or SiC [see Fig.1(a)]. A remaining problem with such nanostructures is the thermal activation of deep levels/surface states which act to substantially reduce the efficiency of the near band edge (NBE) emission at room temperature [see Fig.1(b)]. In this project we will explore passivation of the surface related non-radiative recombination by coating the nanostructures with appropriate polymers. The investigated nanostructures will be fabricated by two different methods: Chemical bath deposition (CBD) as well as atmospheric pressure metal organic chemical vapor deposition (APMOCVD) [1].

Reference: [1] V. Khranovskyy, et al., Physica B (2011), doi:10.1016/j.physb.2011.09.080

Previous projects - highlights 2010

Photonic crystals with carbon nanofibers

H. Arwin, R. Magnusson IFM
R. Renhammar CTH
Photonic crystals based on vertically aligned carbon   nanofibers grown with plasma-CVD in quadratic,   rectangular and random lattices were studied with   ellipsometry and photonic band gaps were determined.   These types of structures are optically complicated, with geometric effects both from the lattice and from individual scatterers.

Epitaxially grown MAX material for improved performance of FET sensors

Kristina Buchholt Anita Lloyd Spetz, IFM
MAX material contacts are developed for SiC FET sensors in order to improve the long term stable   operation temperature of the devices to at least 700°C. The potential of magnetron sputtered,epitaxially   grown Ti3SiC2(0001) as an ohmic contact material to 4H-SiC(0001) is investigated using transmission line model measurements (TLM). In-depth material characterization and study of the growth mode of Ti3SiC2 on 4H-SiC is performed using transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy(AFM),elastic recoil detection analysis (ERDA) and helium ion microscopy (HIM).

Previous projects - highlights 2009

Can nano-pyramids help us in future energy savings?

P-O Holtz, IFM
Energy savings on illumination reaching almost 90 % are predicted if conventional light bulbs are replaced by efficient light emitting diodes. However, the diodes used today have still a too low efficiency due to the fact that the semiconductor material generally used for this purpose, gallium nitride, has a too high defect level, which limits the radiative emission efficiency. In order to circumvent this problem, researchers at IFM have introduced gallium nitride based micro-pyramids

Nanoparticles for biomedical imaging

L. Selegård,   K. Uvdal, IFM
Nano Science and nanotechnology enable design of material and structures with unique material properties. Nanomaterial with such unique properties, in combination with biomolecular self-assembly opens up for new applications, powerful within medicine. We are now developing magnetically and optically active nanoprobes for biomedical imaging. Detailed information of properties of the core, as chemical composition, surface states and defects, magnetic response, optical activity are investigated.

Previous projects - highlights 2008

ZnO nanorods

Lili Yang  Qingxiang Zhao, ITN

The aim of this project is to develop an effective way to control ZnO growth with high reproducibility (control orientation, diameter and density of nanorods) and to investigate fundamental physics involved in ZnO nanorods, nanotubes and nanodots in order to utilize their applications.
Following issues are in focus: Polariton versus diameter, length of ZnO nanorods and nanotubes, excitons such as the free exciton, bound exciton, biexciton and charge exciton depend on geometry of ZnO nanorods, nanotubes and nanodots and whispering gallery modes in ZnO nanotubes.

Atomic Force Measurements for Studies of forces Involved in Protein Folding

Daniel Aili, Fengi Tai, Thomas Ederth, Bo Liedberg, IFM

Synthetic polypeptides with controllable folding properties have been utilized as a molecular Lego for self-assembly of complex nanostructures. Applications range from nanoelectronics to biosensors. This project has been focused on understanding the assembly-mechanisms and forces involved in dimerization and folding of these polypeptides, which is essential for further development of new building nano-Lego building blocks.


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Last updated: 12/05/17