arXiv subjects

Jiří Houška

Publications and source records attributed to Jiří Houška.

4 recordsLinked to original sources

arXiv2026

Bias Tunable Transport Modulation and Gas Selectivity in Layered BiOI: A DFT NEGF Study

Understanding the interplay between adsorption energetics and charge-transport modulation is essential for the rational design of low-power and bias-tunable gas sensors. Here, we present a comprehensive first-principles study of gas selectivity in layered bismuth oxyiodide (BiOI) by integrating density functional theory with nonequilibrium Green's function transport calculations. The adsorption and bias-dependent transport responses toward NO2, NH3, CO2, and representative volatile organic compounds are systematically examined. While NH3 and NO2 exhibit strong chemisorption and localized electronic perturbations, CO2 interacts through weak physisorption, demonstrating that adsorption strength alone does not determine sensing performance. Instead, the evolution of transmission channels near the Fermi level governs the sensing response. Bias-dependent calculations reveal an electrically tunable sensitivity hierarchy, in which weakly adsorbed CO2 preserves conductive pathways and exhibits pronounced low-bias sensitivity despite minimal charge transfer. Recovery-time analysis further highlights the trade-off between transport modulation and reversibility for strongly adsorbed species. These results establish a transport-centered selectivity framework for layered BiOI and provide mechanistic insight into electric-field-controlled gas sensing under ambient conditions.

cond-mat.mtrl-sci↗

arXiv2026

Boron-assisted stabilization of low-resistivity mixed-valence Cu-O thin films prepared by reactive magnetron sputtering

This study systematically investigated the influence of boron incorporation in Cu-O thin films and the effect of oxygen partial pressure ($p_{\rm ox}$) on the phase evolution, chemical bonding, and electrical characteristics of the prepared films. A phase transition from Cu$_2$O to Cu$_2$O/Cu$_4$O$_3$ to CuO was observed as oxygen partial pressure increased. Boron incorporation significantly broadened the stability window of the Cu$_2$O and Cu$_4$O$_3$ phases and delayed the transition to CuO at higher oxygen partial pressure. In the highly B-doped Cu-O films, Cu$_4$O$_3$ was stabilized even under oxygen-rich conditions along with the CuO phase, suggesting that boron significantly altered the oxidation pathway. The formation of B-O and possible B-O-Cu configurations altered the local oxygen chemistry and promoted mixed-valence copper oxide phases. Electrical measurements revealed that highly B-doped Cu-O films exhibited a delayed transition from a high-resistivity low-$p_{\rm ox}$ regime to a low-resistivity mixed-valence regime, ultimately reaching approximately 0.06 $Ω$ cm, among the lowest reported resistivities for a CuO-like material. These findings demonstrate that boron doping is an effective approach for tailoring the phase stability, defect chemistry, and electrical characteristics of Cu-O thin films for optoelectronic and photovoltaic applications.

cond-mat.mtrl-sci↗

arXiv2025

Ultra-low-resistivity nitrogen-doped p-type Cu2O thin films fabricated by reactive HiPIMS

We have successfully fabricated the nitrogen-doped cuprous oxide thin films on the amorphous standard soda-lime glass by reactive high-power impulse magnetron sputtering. The energy of film-forming particles was controlled by the value of pulse-averaged target power density, which has a significant impact on the elemental composition, structure and optoelectrical properties of the films. We have shown that the high-energy regime is more suitable for preserving Cu2O structure and leads to continuous substitution of oxygen by nitrogen compared with the low-energy regime. Moreover, in the high-energy regime, it is possible, to some extent, to independently control the electrical resistivity and optical properties. The electrical resistivity decreases down to 5 x10-2 ohm.cm at the optical band gap 2.0-2.3 eV. Special attention is paid to the formation of nitrogen molecules and their ability to form shallow acceptor states. Experimental results supported by our DFT calculations indicate that N2 replacing Cu in the Cu2O lattice is one possible (but not the only possible) acceptor. We have also found that the formation of nitrogen molecules is preferred in a high-energy regime.

cond-mat.mtrl-sci↗

arXiv2024

Extraordinary oxidation behavior of W-Zr thin-film metallic glasses: A route for tailoring functional properties of W-Zr-O films

The oxidation behavior of W-Zr thin-film metallic glasses (TFMGs) with 32, 48 and 61 at.% Zr, prepared by dc magnetron co-sputtering, was comprehensively studied after annealing in synthetic air. The study focuses on the effect of the annealing temperature (up to 600°C) on the oxidation process, oxygen saturation, structure evolution, and their subsequent impact on electrical, optical and mechanical properties. The findings reveal that controlled oxidation transforms W-Zr TFMGs into amorphous ceramic W-Zr-O films with substoichiometric compositions. This is a consequence of an oxidation process that does not proceed through the formation of a stoichiometric oxide layer on the surface of W-Zr TFMGs, acting as a diffusion barrier against fast oxidation, but leads to a gradual incorporation of oxygen across the film volume due to thermodynamics factors. Higher Zr content accelerates the oxygen incorporation and its depth uniformity in the films. As a result, the mechanical properties are significantly enhanced achieving hardness values of up to 17.5 GPa at approximately 50% oxygen saturation. Simultaneously, the electrical and optical properties are finely tuned with the resistivity and the extinction coefficient (measured at 550 nm) ranging from 1.7 to 95.7x10-4 Ohm.cm and 0.28 to 1.06, respectively.

cond-mat.mtrl-sci↗