Jirí Houška

University of West Bohemia · Department of Physics

Amorphous SiBCN alloys are known - depending on the elemental composition - for their thermal stability and high-temperature (up to 1500 °C) oxidation resistance, hardness, optical transparency or electrical and/or thermal conductivity. The paper reports ageing of SiBCN ceramics prepared in the form of thin films in a wide range of elemental compos...

Amorphous Si-B-C-N alloys were deposited by reactive magnetron sputtering, and their high-temperature stability was investigated using a combined approach of experiment and molecular-dynamics simulations. We show that both a higher Si/C ratio and the addition of boron improve the thermal stability of the materials. We find that lifetimes of bonds o...

We performed classical molecular dynamics simulations of thermodynamically preferred structures of Ti(50-x)SixN50 (x≤0.3) nanocomposites of various compositions containing up to a quarter of million of atoms. We focus on the formation and growth of TiN nanocrystals, and investigate how the Si content affects their number, size distribution, Si cont...

We study the hard and electrically conductive multicomponent diboride Ti0.25Zr0.25Hf0.25Ta0.25B2 with high thermal stability by ab initio calculations. We focus on the effect of defects (either vacancies or C atoms, both relevant for numerous experiments including our own) on material characteristics. Different types, concentrations and distributio...

The growth of crystalline ZrO2 is studied by a combined approach of atom-by-atom growth simulations, high-power impulse magnetron sputtering and conventional pulsed magnetron sputtering. We focus on the energy of arriving atoms of various elements, and investigate how does it affect the growth of ZrO2 crystals of various orientations. The results a...

Amorphous Si-B-C-N alloys can combine exceptional oxidation resistance up to 1500 °C with high-temperature stability of superior functional properties. Because some of these characteristics require as high N content as possible, the maximum achievable N content in amorphous Si-B-C-N is examined by combining extensive ab initio molecular dynamics si...

We report high-quality, hard (31-41 GPa), crack-resistant (hardness-to-effective Young's modulus ratio of 0.13-0.16) and electrically conductive (2.8-4.2 × 10 5 S.m-1) HfB2-based ceramic materials with high thermal stability. The materials were prepared in the form of well adhesive films using a simple deposition process: pulsed magnetron sputterin...

The measured properties of constituent materials of experimentally prepared ZrO2/V1-zWzO2/ZrO2 thermochromic coatings with a low transition temperature are used to optimize the coating performance by varying the thicknesses of individual layers. The main attention is paid to the optimization of coating color in transmission, with the aim to shift i...

We report high-quality, hard (31–41 GPa), crack-resistant (hardness-to-effective Young's modulus ratio of 0.13–0.16) and electrically conductive (2.8–4.2 × 10⁵ S m⁻¹) HfB2-based ceramic materials with high thermal stability. The materials were prepared in the form of well adhesive films using a simple deposition process: pulsed magnetron sputtering...

We report on the microstructure of high-performance thermochromic ZrO2/V0.984W0.016O2/ZrO2 coating deposited on ultrathin flexible glass using a pulsed magnetron sputtering without any substrate bias voltage and post-deposition annealing. The coating combines a low transition temperature of 22 °C, an integral luminous transmittance approaching 50%...

Amorphous HfMSiBCN materials (M = Y, Ho, Ta, Mo or an enhanced Hf content instead of any other M) are investigated by ab-initio calculations and magnetron sputtering. We focus on combining the high-temperature stability and oxidation resistance of these materials with optimised mechanical, optical and electrical properties. First, we predict the co...

Reactive deep oscillation magnetron sputtering with a pulsed reactive gas flow control and to-substrate reactive gas injection into the high-density plasma in front of the sputtered Mo target was used for a low-temperature (< 120 °C) preparation of MoOx and MoOxNy films with 2.5 < x < 3.0 and y < 0.2. We explain the advantages of this deposition te...

The reversible semiconductor-to-metal transition of vanadium dioxide (VO2) makes VO2-based coatings a promising candidate for thermochromic smart windows, reducing the energy consumption of buildings. This paper deals with maximizing the application potential of these coatings in terms of their performance, an industry-friendly preparation techniqu...

Hard and optically transparent amorphous Hf7B10Si32C2N44, Hf6B12Si29Y2C2N45 and Hf5B13Si25Ho3C2N48 films were prepared and examined for the oxidation resistance in air and thermal stability in inert gasses up to 1600 °C. A thermal evolution of their structure, hardness and optical properties was also studied. An addition of Y or Ho (2–3 at.%) into...

The maximum achievable N content in atom-by-atom growth of Si-C-N films is examined by combining ab-initio molecular dynamics simulations in a wide range of compositions and densities with experimental data. When and only when the simulation algorithm allows the formation and final presence of N2 molecules, the densities leading to the deepest loca...

We report on high-performance thermochromic ZrO2/V0.982W0.018O2/ZrO2 coatings with a low transition temperature prepared on glass by a low-temperature scalable deposition technique. The V0.982W0.018O2 layers were deposited by a controlled high-power impulse magnetron sputtering of V target, combined with a simultaneous pulsed DC magnetron sputterin...

High-power impulse magnetron sputtering of a Ta target in precisely controlled Ar+O2+N2 gas mixtures was used to prepare amorphous N-rich tantalum oxynitride (Ta–O–N) films with a finely varied elemental composition. Postdeposition annealing of the films at 900°C for 5 min in vacuum led to their crystallization without any significant change in the...

We report a low-temperature deposition of Al-O-N films in a wide range of compositions. We use and explain the advantages of reactive deep oscillation magnetron sputtering (leading to suppressed arcing on the Al target) with a pulsed reactive gas flow control and optimized reactive gas inlet position (leading to a very smooth composition control, d...

The self-organization of macromolecules on solid surfaces represents a topic of great current interest. Here, solvent-free interactions between polyolefins and silicon substrates are investigated upon their physical vapor deposition under vacuum. Molecular dynamics simulations show that polyolefins unfold upon adsorption and that two macromolecules...

The high-temperature behavior of an electrically conductive, opaque and hard Hf7B23Si22C6N40 ceramic film with an amorphous structure was systematically investigated in air up to 1700 °C and inert gases up to 1600 °C. The film was prepared by reactive pulsed dc magnetron sputter deposition in an argon‑nitrogen gas mixture. The study is focused on t...

We investigate the oxidation of a wide range of metal surfaces by ab-initio calculations. We go through a wide range of metals (Sc, Y, La, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Cu, Ag, Au, Zn, Cd, Al) and surface oxygen coverages (ΘO). Calculations of the adsorption energy per O atom (Eads_min) are followed by characterizing the preferred distribution...

Extensive molecular dynamics simulations of the atom-by-atom growth of Zr–Cu films were performed in a wide range of compositions, energies and growth templates. The results are correlated with and used to explain experimental results obtained using magnetron sputtering of the same films. After the identification of compositional ranges correspondi...

Structures of amorphous CNx materials are predicted by extensive ab-initio molecular-dynamics simulations (more than 800 trajectories) in a wide range of compositions and densities. The main attention is paid to the formation of N2 molecules, with the aim to predict and explain the maximum N content in stable CNx networks. The results show that the...

Reactive high-power impulse magnetron sputtering was used for high-rate (deposition rate of 60 nm/min) deposition of conductive (resistivity of 3 × 10 ⁻³ Ωcm) and optically transparent (extinction coefficient at the wavelength of 550 nm of 0.01) ZnO:Al thin films at ambient temperature (< 40 °C). We used planar Zn:Al target (3.09 at.% of Al) with d...

The paper deals with VO2-based thermochromic coatings prepared by reactive magnetron sputtering. We combine four ways how to improve the coating performance and to increase its application potential. First, reactive high-power impulse magnetron sputtering with a pulsed O2 flow control allowed us to prepare crystalline VO2 of the correct stoichiomet...

The paper reports on the structure, microstructure, mechanical and tribological properties and oxidation resistance of WNx films with a stoichiometry x = [N]/[W] ranging from 0 to 1.5 prepared by magnetron sputtering. It was found that (i) films with x ≤ 0.20 exhibit α-W structure and columnar microstructure, while films with x ≥ 0.27 exhibit β-W2N...

The ion-flux characteristics at a substrate position and the corresponding discharge characteristics were investigated during controlled low-temperature (300 °C) reactive high-power impulse magnetron sputtering (HiPIMS) depositions of thermochromic VO2 films onto conventional soda-lime glass substrates without any substrate bias voltage and without...

High power impulse magnetron sputtering of a Ta target in various Ar+O2+N2 gas mixtures was utilized to prepare amorphous tantalum oxynitride (Ta–O–N) films with a finely controlled elemental composition in a wide range. We investigate the effect of film annealing at 900°C in vacuum on structure and properties of the films. We show that the finely...

Reactive high-power impulse magnetron sputtering (HiPIMS) was used for deposition of amorphous In-Ga-Zn-O films at low substrate temperature (<70 °C). The depositions were performed using a strongly unbalanced magnetron equipped with a ceramic In2Ga2ZnO7 target (100 mm in diameter). Films were prepared at a constant argon pressure of 1 Pa on standa...

The paper deals with thermochromic VO2/SiO2 coatings prepared by low-temperature pulsed reactive magnetron sputtering on conventional soda-lime glass substrates without any substrate bias and without any interlayer. Thermochromic VO2 layers were deposited using reactive high-power impulse magnetron sputtering with a pulsed O2 flow control at a subs...

The paper deals with thermochromic VO2 films deposited by reactive high-power impulse magnetron sputtering with a pulsed reactive gas flow control under exceptionally industry-friendly conditions: onto amorphous glass substrates without any interlayer, without any substrate bias voltage and at low temperatures (Tdep) down to 300 °C. We show that (a...

The paper deals with Hf–B–Si–C–N films deposited onto Si and SiC substrates using pulsed magnetron co-sputtering of a single B4C–Hf–Si target (at fixed 15% Hf and 20% Si fractions in the target erosion area) in argon–nitrogen gas mixtures. We focus on the effect of the nitrogen fraction in the gas mixture (in the range from 0% to 50%) and of the vo...

The paper reports on the thermal stability of two ternary Zr–Ta–O films (Zr25Ta5O70, Ta25Zr5O70) and two binary oxide films (ZrO2, Ta2O5) prepared by reactive high-power impulse magnetron sputtering using a pulsed reactive gas flow control. The thermal stability of the structure, microstructure, mechanical and optical properties of the films was in...

Reactive mid-frequency ac magnetron sputtering with a pulsed reactive gas (oxygen) flow control was used for high-rate depositions of defect-free, hard and highly optically transparent stoichiometric ZrO2 films onto floating substrates. The depositions were performed using two strongly unbalanced magnetrons in a closed-field configuration. We used...

Reactive high-power impulse magnetron sputtering with a pulsed O2 flow control and to-substrate O2 injection into a high-density plasma in front of the sputtered vanadium target was used for low-temperature (300 °C) deposition of VO2 films with a pronounced semiconductor-to-metal transition onto conventional soda-lime glass substrates without any s...

We investigate the oxidation of selected metal (Al, Ag, Cu, Ti, Zr, and Hf) surfaces by the density functional theory. We go through a wide range of (233 per metal) distributions of O atoms on a partially oxidizedmetal surface. First, we focus on the qualitative information whether the preferred distribution of O atoms is heterogeneous (stoichiomet...

The paper deals with the development and subsequent testing of a Buckingham interaction potential which allows one to correctly describe the atom-by-atom growth of TiO2. Contrary to the most frequent procedures of the interaction potential development, correct coordination numbers which the potential leads to in an open surface growth are included...

The paper deals with the methodology of film growth simulations using classical molecular dynamics and an empirical interaction potential. We focus on the effect of the cut-off distance (rC) of the short-range part of the potential. On the one hand, we find that rC does not affect the qualitative conclusions of the simulations and that its quantita...

High-power impulse magnetron sputtering with a pulsed O2 flow control was used for reactive deposition of densified stoichiometric ZrO2 films with gradient ZrOx interlayers onto floating Si and steel substrates at low substrate temperatures (less than 150 °C). The depositions were performed using a strongly unbalanced magnetron with a planar Zr tar...

Hafnium oxynitride ceramics were prepared in the form of thin films by high-power impulse magnetron sputtering of Hf in various Ar+O2+N2 gas mixtures. Smooth composition control was achieved by maximizing the degree of dissociation in plasma, suppressing the importance of the difference between reactivities of undissociated O2 and N2. The applicati...

Reactive high-power impulse magnetron sputtering was used to deposit HfO2 films on Si substrates using a voltage pulse duration, t1, from 100 to 200 μs and an deposition-averaged target power density, < Sd >, from 7.2 to 54 Wcm− 2. The effects of these processing parameters on the microstructure and properties of the films were studied by atomic fo...

The paper deals with MSiBCN (M = Ti, Zr, Hf) thin films prepared by pulsed dc reactive magnetron sputtering of M15Si20(B4C)65 targets. We focus on the effect of M choice and N2 + Ar discharge gas mixture composition. The experimental results are complemented and explained by ab-initio calculations. We find that the transition from Ti through Zr to...

The paper deals with thermochromic VO2 prepared by reactive high-power impulse magnetron sputtering and characterized by spectroscopic ellipsometry. We focus on the dispersion of optical constants in a wide temperature range and on the transmittance predicted using the optical constants. While the thermochromic behavior of VO2 in itself has been re...

Thin films of ZrO2 are of high interest due to a wide range of useful technological properties. Previously, the plasma-assisted preparation of ZrO2 has been described in terms of extrinsic process parameters such as total pressure, oxygen partial pressure or discharge power. In this paper the growth of ZrO2 is studied by atom-by-atom molecular dyna...

High-power impulse magnetron sputtering (HiPIMS) with a pulsed reactive gas (oxygen) flow control was used for high-rate reactive depositions of densified, highly optically transparent, stoichiometric HfO2 films onto floating substrates. The depositions were performed using a strongly unbalanced magnetron with a directly water-cooled planar Hf targ...

We study the thermal, mechanical and electrical properties of B4C, BCN, ZrBC and ZrBCN ceramics prepared in the form of thin films by magnetron sputtering. We focus on the effect of Zr x (B4C)1-x sputter target composition, the N2+Ar discharge gas mixture composition, the deposition temperature and the annealing temperature after the deposition. Th...

The present study focuses on the effect of Cu incorporation into magnetron sputtered alumina films. The transformation phenomena in an Al-O film and Al-Cu-O films with varying Cu content (1.4-9.6 at%) were studied using differential scanning calorimetry (DSC) and X-ray diffraction in combination with ab-initio calculations. In the Al-O film, only a...

High-power impulse magnetron sputtering with a pulsed reactive gas (oxygen) flow control was used for high-rate reactive depositions of densified, highly optically transparent, stoichiometric ZrO2 films onto floating substrates. The depositions were performed using a strongly unbalanced magnetron with a directly water-cooled planar Zr target of 100...

Hf-B-Si-C films were deposited onto silicon and glass substrates using pulsed magnetron co-sputtering of a single B4C-Hf-Si target (at a fixed 15% Hf fraction and a varying 0–50% Si fraction in the target erosion area) in pure argon. We focus on the effect of the Si content in the films. The film structure changes from nanocolumnar (at 0–7 at.% of...

Pulsed reactive magnetron sputtering was used to deposit Zr–B–C–N films as a function of the N2/Ar ratio in the plasma. The microstructure evolution of the films was studied by high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy and nanoindentation. Zr–B–C–N films with a chemical composition (in at.% without 1–2 at.%...

High-power impulse magnetron sputtering of a planar Ta target in various Ar + O2 + N2 gas mixtures was investigated at an average target power density close to 50 W cm− 2 during a deposition. A strongly unbalanced magnetron was driven by a pulsed dc power supply operating at the repetition frequency of 500 Hz and the average target power density of...

The presence of a small fraction of high-energy particles in the total particle flux is an important factor which affects the structure of atom-by-atom deposited thin films. In this paper the role of high-energy (up to 400 eV) particles is studied by molecular dynamics simulations, focused on obtaining quantitative information not accessible experi...

High-power impulse magnetron sputtering with a pulsed reactive gas (oxygen) flow control was used for high-rate reactive depositions of densified stoichiometric ZrO2 and Ta2O5 films onto floating substrates. The depositions were performed using a strongly unbalanced magnetron with a planar zirconium or tantalum target of 100 mm diameter in argon-ox...

The paper deals with characteristics of a wide range of ternary and quaternary metal nitrides (M = Ti, Zr, Hf, V, Nb or Ta) of various compositions obtained by ab initio calculations. We focus on the formation energies (E form), bulk moduli (B), shear moduli (G) and a difference of B and G from the weighted average of B and G of binary metal nitrid...

Thin films of crystalline TiO{sub 2} are of high interest due to their photoactivity and photoinduced hydrophilicity. Previously, preparation of TiO{sub 2} has been described in terms of extrinsic process parameters, such as total pressure, oxygen partial pressure, or substrate bias potential. We study the growth of TiO{sub 2} phases, rutile and an...

We study optical properties of Al2O3 films prepared by various techniques using spectroscopic ellipsometry. The film preparation techniques include conventional pulsed magnetron sputtering in various gas mixtures, high power impulse magnetron sputtering, annealing of as-deposited Al2O3 in an inert atmosphere and annealing of as-deposited Al in air....

The article reports on the effect of the addition of copper in the Al2O3 film on its mechanical and optical properties. The Al–Cu–O films were reactively co-sputtered using DC pulse dual magnetron in a mixture of Ar + O2. One magnetron was equipped with a pure Al target and the second magnetron with a composed Al/Cu target. The amount of Al and Cu...

Amorphous SiBCN materials were prepared using reactive magnetron sputtering, and their structure, electronic structure and electrical and optical properties were studied using a combined approach of experiment and ab initio calculations. We focus on the effect of N content over a wide range on the material properties. We find that decreasing the N...

Binary and ternary amorphous transition metal (TM) nitrides and oxides are of great interest because of their suitability for diverse applications ranging from high-temperature machining to the production of optical filters or electrochromic devices. However, understanding of bonding in, and electronic structure of, these materials represents a cha...

The paper contains a detailed discussion of the electronic structure of the novel hard and thermally stable amorphous SiBCN materials. We focus on the weight of individual electronic states on different elements, bond types, bonds of different lengths, and the number of atoms and clusters of atoms the states are localized on. A special attention is...

Amorphous hydrogenated silicon nitride (SiNH) materials prepared by plasma-enhanced chemical vapor deposition (PECVD) are of high interest because of their suitability for diverse applications including optical coatings, gas/vapor permeation barriers, corrosion resistant, and protective coatings and numerous others. In addition, they are very suita...

It has previously been noted that two types of hydrogen exist in hydrogenated amorphous carbon (a-C:H) prepared by chemical vapor deposition techniques: H bonded to C atoms and unbonded H2 molecules (up to 80% of all H). Little is known on the atomic-scale processes during the formation of the structures containing unbonded hydrogen, and on the eff...

It has previously been noted that different fcc metal nitrides exhibit different superior properties, including the high hardness of TiN and the excellent corrosion and oxidation resistance of CrN. Si and C have been added into such metal nitrides in order to tailor their functional properties. Contrary to the intensively studied TiSiN and TiCN nan...

The effect of the gas mixture composition on the high-temperature behavior of amorphous Si–B–C–N coatings was systematically investigated up to 1700 °C in a flowing air and inert gases (He and Ar). The Si–B–C–N coatings were deposited by reactive dc magnetron co-sputtering using a single B4C–Si target in two nitrogen–argon gas mixtures (50% N2 + 50...

Quaternary Si–B–C–N films were prepared using reactive direct current magnetron co-sputtering of silicon, boron and carbon from a single C–Si–B target in nitrogen–argon gas mixtures at substrate temperatures of 180–350 °C. We focused on complex relationships between process parameters, elemental composition, bonding structure, and mechanical, tribo...

Amorphous silicon-boron-carbon-nitrogen alloys were deposited by reactive magnetron sputtering, and their bonding statistics and electronic structure were investigated using a combined approach of experiment and molecular dynamics simulations. The authors show a difference between Si-based and C-based Si-B-C-N networks, and investigate coordination...

Energy-resolved mass spectroscopy was used to investigate differences in ion-bombardment characteristics during conventional reactive magnetron sputtering of TiN films and their deposition using a grid-assisted magnetron system with anode at a high potential (up to 350 V relative to grounded chamber walls). Narrow ion energy distributions with a ma...

Amorphous silicon–boron–carbon–nitrogen alloys were deposited by reactive magnetron sputtering in nitrogen–argon gas mixtures, and their structure and resulting mechanical properties were investigated using a combined approach of experiment and molecular-dynamics simulations. We show a difference between structures of the materials deposited with a...

We systematically investigated the effect of the rf induced negative substrate bias voltage, U b , on characteristics of novel quaternary Si–B–C– N films. The films were deposited on Si(100) or glass substrates by reactive dc magnetron co-sputtering of silicon, boron and carbon from a single C–Si–B or B 4 C–Si target in nitrogen–argon gas mixtures...

It has previously been noted that the implantation of argon atoms into amorphous SiBCN materials (prepared by magnetron sputtering in various N2+Ar mixtures) leads to variations in a number of material properties; for example an increase in compressive stress. Little is known about the mechanism by which Ar incorporation affects structural and mech...

Based on the results obtained for C–N and Si–C–N films, a systematic investigation of reactive magnetron sputtering of hard quaternary Si–B–C–N materials has been carried out. The Si–B–C–N films were deposited on p-type Si100 substrates by dc magnetron co-sputtering using a single C–Si–B target at a fixed 20% boron fraction in the target erosion ar...

The Ti film deposited by grid-attached magnetron sputtering possesses mirror-like surface RMS roughness of 0.6∼1.3 nm. On the other hand, Ti film deposited by conventional magnetron sputtering possesses a steeply increased RMS surface roughness of 6 nm. The cross-sectional TEM micrographs indicated that Ti coating by conventional process was compos...

We report ab initio molecular dynamics simulations of the preparation of CNx , BCN, and SiBCN materials formed by energetic-ion-assisted deposition techniques. We focus on the formation of N2 molecules during liquid-quench simulations and investigate how density, temperature, and quench rate affect the number of N2 molecules formed in the network....