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Implemented projects 
Latvian Council of Science Projects


Total cost: 497 580 EUR

Duration: 01.07.2020. - 31.12.2020

The Institute of Solid State Physics, together with other institutions, participates in the implementation of the project, which is related to the solution of problems related to COVID-19. The overall goal of the project is to provide medical institutions with up-to-date information and technologies that will help reduce the risk of infection and reduce the workload of medical staff.
Within the framework of the project, the Institute of Solid State Physics study the anti-microbial effect of different types of WO3-x, WO3-x:Cu, Cu, WO3-x/Cu/WO3-x thin coatings, as well as the possibilities of improving the chemical and mechanical strength of these coatings.
Magnetron sputtering technology is used to obtain coatings. Variation of process parameters provides an opportunity to obtain coatings with different physical-chemical properties, and to variate chemical composition.
Obtained coatings ability to transmit visible light provides the possibility to use coatings on protective screens, contact surfaces, and in protective suits visors. The possibilities of practical application of the developing prototype correspond to the project goals.
Project implementation process:
At the beginning of 09.2020, the first batch of samples was tested, anti-microbial activity was observed for several coating types, also physical-chemical properties were tested.
Based on the previously collected data, a second batch of test samples was prepared.

Total cost: 200 000 EUR

Duration (years): 2018-2020

LZP FLPP No.LZP-2018/2-0353

Searching for new high temperature superconductors which could be used in everyday applications is nowadays one of the most important and challenging problems in physics and materials science. A huge step forwad has been made in 2015, when superconductivity has been discovered in hydrogen sulfide with the record-hight critical temperature Tc = 203K. Although the physical mechanisms responsible for superconductivity are known, more detailed experimental information about behaviour of the electrons and their coupling with the phonons is requied. In this project we aim to obtain new information about the evolution of the electronic and the local atomic structures in hydrogen rich metal hydrides as temperature and pressure (200 GPa) are varied. We will apply the novel microbeam synchrotron-radiation based X-ray absorption fine structure (XAFS) technique at extreme pressure. The Y-H and La-H systems, will be examined where new hydrogen-rich phases are predicted to be formed with the Tc higher than in supfur hydride. The structural information obtained by advanced ab-initio XAFS analysis including including Reverse Monte Carlo will be compared with the theoretically predicted superconducting phases. The project is multidisciplinary and combines materials science, synchrotron radiation technique at extreme pressure, solid state chemistry, physics and computer science.


ABSTRACT: The discovery of superconductivity above 250 K at high pressure in LaH10 and the prediction of overcoming the room temperature threshold for superconductivity in YH10 urge for a better understanding of hydrogen interaction mechanism with the heavy atom sublattice in metal hydrides under high pressure at the atomic scale. Here we use locally sensitive X-ray absorption fine structure spectroscopy (XAFS) to get insight into the nature of phase transitions and the rearrangements of local electronic and crystal structure in archetypal metal hydride YH3 under pressure up to 180 GPa.
The combination of the experimental methods allowed us to implement a multiscale length study of YH3: XAFS (short-range), Raman scattering (medium-range) and XRD (long-range). XANES data evidence a strong effect of hydrogen on the density of 4d yttrium states that increases with pressure and EXAFS data evidence a strong anharmonicity, manifested as yttrium atom vibrations in a double-well potential.

Nature Communications (in press 2021)

ABSTRACT: High pressure energy-dispersive X-ray absorption spectroscopy is a valuable structural technique, especially, when combined with a nano-polycrystalline diamond anvil cell. Here we present recent results obtained using the dispersive setup of the ODE beamline at SOLEIL synchrotron. The effect of pressure and temperature on the X-ray induced photoreduction is discussed on the example of nanocrystalline CuO. The possibility to follow local environment changes during pressure-induced phase transitions is demonstrated for α-MoO (Formula presented.) based on the reverse Monte Carlo simulations. © 2020, © 2020 Informa UK Limited, trading as Taylor & Francis Group.

High Pressure Research, 40 (2020) 82–87.
DOI: 10.1080/08957959.2019.1700979
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ABSTRACT: Scandium fluoride (ScF3) belongs to a class of negative thermal expansion (NTE) materials. It shows a strong lattice contraction up to about 1000 K switching to expansion at higher temperatures. Here the NTE effect in ScF3 is studied in the temperature range from 300 K to 1600 K using ab initio molecular dynamics (AIMD) simulations in the isothermal-isobaric (NpT) ensemble. The temperature dependence of the lattice constant, inter-atomic Sc–F–Sc bond angle distributions and the Sc–F and Sc–Sc radial distribution functions is obtained as a function of supercell size from 2a × 2a × 2a to 5a × 5a × 5a where a is the lattice parameter of ScF3. A comparison with the experimental Sc K-edge EXAFS data at 600 K is used to validate the accuracy of the AIMD simulations. Our results suggest that the AIMD calculations are able to reproduce qualitatively the NTE effect in ScF3, however a supercell size larger than 2a × 2a × 2a should be used to account accurately for dynamic disorder. The origin of the NTE in ScF3 is explained by the interplay between expansion and rotation of ScF6 octahedra. © 2019 Elsevier B.V.

(2020) Computational Materials Science, 171, art. no. 109198, .
DOI: 10.1016/j.commatsci.2019.109198
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ABSTRACT: Two pressure-induced phase transitions have been theoretically studied in the layered iron phosphorus triselenide (FePSe3). Topological analysis of chemical bonding in FePSe3 has been performed based on the results of first-principles calculations within the periodic linear combination of atomic orbitals (LCAO) method with hybrid Hartree-Fock-DFT B3LYP functional. The first transition at about 6 GPa is accompanied by the symmetry change from (Formula presented.) to C2/m, whereas the semiconductor-to-metal transition (SMT) occurs at about 13 GPa leading to the symmetry change from C2/m to (Formula presented.). We found that the collapse of the band gap at about 13 GPa occurs due to changes in the electronic structure of FePSe3 induced by relative displacements of phosphorus or selenium atoms along the c-axis direction under pressure. The results of the topological analysis of the electron density and its Laplacian demonstrate that the pressure changes not only the interatomic distances but also the bond nature between the intralayer and interlayer phosphorus atoms. The interlayer P–P interactions are absent in two non-metallic FePSe3 phases while after SMT the intralayer P–P interactions weaken and the interlayer P–P interactions appear. © 2020 Wiley Periodicals LLC

(2020) Journal of Computational Chemistry, 41 (31), pp. 2610-2623.
DOI: 10.1002/jcc.26416
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ABSTRACT: The ferroelectric distortions in perovskites were a subject of numerous investigations for a long time. However, some controversial results still exist, coming from the analysis of diffraction (X-ray, neutron or electron) data and X-ray absorption spectra. In this study, our goal was to revisit these classical materials using recently developed methods without imposing any predefined structural model. Local environment around A-type atom in ABO3 perovskites (SrTiO3, BaTiO3, EuTiO3) was studied by X-ray absorption spectroscopy (XAS) in a wide range of temperatures (20–400 K). Using reverse Monte Carlo method enhanced by evolutionary algorithm, the 3D structure was extracted from the extended X-ray absorption fine structure (EXAFS) and interpreted in terms of the radial distribution functions (RDFs). Our findings show that both diffraction and XAS data are consistent, but reflect the structure of the material from different points of view. In particular, when strong correlations in the motion of certain atoms are present, the information obtained by XAS might lead to a different from expected shape of the RDF. At the same time, the average positions of all atoms are in good agreement with those given by diffraction. This makes XAS an important technique for studying interatomic correlations and lattice dynamics. © 2019 Elsevier Ltd

(2020) Radiation Physics and Chemistry, 175, art. no. 108072, .
DOI: 10.1016/j.radphyschem.2018.11.026
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ABSTRACT: Pressure-induced insulator-to-metal transition (IMT) has been studied in the van der Waals compound iron thiophosphate (FePS3) using first-principles calculations within the periodic linear combination of atomic orbitals method with hybrid Hartree–Fock-DFT B3LYP functional. Our calculations reproduce correctly the IMT at ∼15 GPa, which is accompanied by a reduction of the unit cell volume and of the vdW gap. We found from the detailed analysis of the projected density of states that the 3p states of phosphorus atoms contribute significantly at the bottom of the conduction band. As a result, the collapse of the band gap occurs due to changes in the electronic structure of FePS3 induced by relative displacements of phosphorus or sulfur atoms along the c-axis direction under pressure. © 2020 Wiley Periodicals, Inc.

(2020) Journal of Computational Chemistry, 41 (14), pp. 1337-1344.
DOI: 10.1002/jcc.26178
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ABSTRACT: The electronic and atomic structure of a bulk 2D layered van-der-Waals compound CdPS3 was studied in the low (R3) and room (C2/m) temperature phases using first-principles calculations within the periodic linear combination of atomic orbitals method with hybrid meta exchange-correlation M06 functional. The calculation results reproduce well the experimental crystallographic parameters. The value of the indirect band gap Eg = 3.4 eV for the room-temperature monoclinic C2/m phase is close to the experimental one, while the indirect band gap Eg = 3.3 eV was predicted for the low-temperature trigonal R3 phase. The effect of hydrostatic pressure on the band gap in both phases was studied in the pressure range from 0 to 40 GPa. In both cases, the pressure dependence of the band gap passes through a maximum, but at different pressures. In the R3 phase, the band gap reaches its maximum value of ∼4 eV at ∼30 GPa, whereas in the C2/m phase, the maximum value of ∼3.6 eV is reached already at ∼8 GPa. © 2020 Author(s).

Low Temp. Phys. 46 (2020) 1217-1222.
DOI: 10.1063/10.0002477
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Total cost: 199 508 EUR

Duration (years): 2018-2020

LZP FLPP Nr. lzp-2018/2-0083

The utilization of solar energy to convert water into hydrogen via efficient photocatalysis is an ultimate goal of clean energy society. The current understanding of processes taking place at nanostructured photoelectrode surfaces is insufficient to rationally design the efficient photochemical reactor for visible-light-driven water splitting. Engineering the electronic energy band structure of hybrid nanostructured semiconductor materials through judicious control of their atomic composition is a promising route to increase visible light photoresponse. In this respect, before time-consuming and expensive experimental synthesis of nanophotocatalyst combined with spectroscopy and electrochemical measurements, it is reasonable to perform thorough theoretical modelling of the mid-gap states and band edge positions of promising photoelectrodes. The main goal of our project is to develop a reliable theoretical approach based on multi-scale computer modelling for fundamental understanding of such factors as composition, atomic and electronic structure, and charge transfer processes at hybrid nanostructured photocatalysts vital for their further synthesis and experimental characterization. The project results in improvements in efficiency, durability, and, consequently, the cost of photochemical reactors allowing efficient hydrogen production from water.


Horizon 2020

Duration (years): 2018-2020

Grant agreement No 768789.

The CO2EXIDE project aims at the development of a combined electrochemical-chemical technology for the production of ethylene oxide from biobased CO2. Initially, the electrochemical step pursues the simultaneous conversion of CO2 to ethylene at the cathode and water oxidation to hydrogen peroxide at the anode. A subsequent chemical conversion of both intermediates to ethylene oxide will deliver e.g. oligo-/polyethylene glycol in a chemical cascade reaction. The CO2EXIDE technology combines a modular nature for the feasibility of a decentralised application, a high energy and material efficiency/yield and the substitution of fossil based production of ethylene oxide. In line with the energy turnaround, the CO2EXIDE technology will be combinable with renewables and allows for the direct creation of products, which can be integrated into the existing supply chain. The reactions will be operated at low temperatures and pressures and forecast significant improvements in energy and resource efficiency combined with an enormous reduction of GHG emissions. All improvements will be quantitated using life cycle assessment.
The role of the Institute of Solid State Physics, University of Latvia (ISSP UL) in the project is to create an alternative structure of the cathode for electrocatalytic reduction of CO2 to ethylene, based on modified multi-layer graphene stacks obtained from recycled graphite. In addition, the ISSP UL will perform theoretical calculations from the first principles of the graphene sheet modified with copper atom clusters, and will construct innovative electrochemical half-cell to monitor with FTIR spectroscopy the gases in CO2 reduction process. SPEEK polymer composites with zirconium oxide nanoparticles and ionic liquid derived from imidazole compounds will be developed to form a membrane that is compatible with the catalyst materials and stimulates the adsorption of the CO2 on the electrode.



XAS studies on a 14%Cr ODS alloy and on ion-irradiated RAFM steels (2018 - 2020)
European Regional Development Fund projects

Total budget: 25 000 EUR

Duration: 1.04.2020.-30.09.2020.

Project number: KC-PI-2020/45

The aim of the project is to develop and commercialize cheap nanowire-based photodetectors for the UV-VIS-IR range and nanowire photodetectors for the X-ray range. Inexpensive small photodetectors may be in high demand for the implementation of the Internet of Things concept. Within the first stage of the project, it is planned to carry out a technical and economic feasibility study of the technology transfer project and to develop a commercialization strategy.


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