arXiv subjects

Radomír Čerstvý

Publications and source records attributed to Radomír Čerstvý.

4 recordsLinked to original sources

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↗

arXiv2026

Corrosion-resistant and conductive Ti-Nb-O coatings tailored for ultra-low Pt-loaded BPPs and PTLs in PEM electrolyzers

We develop highly corrosion-resistant and conductive Ti-Nb-O coatings for metallic components -- bipolar plates (BPPs) and porous transport layers (PTLs) -- in PEM water electrolyzers. Using reactive high-power impulse magnetron sputtering (HiPIMS), we deposit compact 200 nm bilayer coatings onto SS316L substrates, systematically tailoring their composition. By precisely controlling oxygen partial pressure and Nb/Ti ratio, we adjust stoichiometry and structure, directly affecting electrical resistivity and corrosion resistance. We examine interfacial contact resistance (ICR) and electrochemical parameters before and after accelerated corrosion testing. Optimized coatings exhibit resistivity on the order of 10^-4 Ohmcm and extremely low corrosion current densities (J_corr = 0.01-0.08 uA/cm^2), well below the U.S. DOE 2026 target. Most importantly, these coatings enable the ICR target after accelerated corrosion testing with a Pt overlayer as thin as 5 nm, reducing Pt loading by up to two orders of magnitude compared to conventional approaches.

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↗

arXiv2025

Thermally-induced microstructural evolution in nanoparticle-based CuO, WO$_3$ and CuO-WO$_3$ thin films for hydrogen gas sensing

This study systematically investigates the microstructural evolution of nanoparticle-based CuO, WO$_3$, and composite 'CuO-WO$_3$' thin films induced by their post-deposition annealing. The films were reactively deposited using a magnetron-based gas aggregation technique, with the composite films consisting of alternating monolayers of CuO and WO$_3$ nanoparticles. After deposition, the films were annealed in synthetic air at temperatures ranging from 200 to 400$^\circ$C and characterized using scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. Annealing of the CuO films led to the most pronounced changes associated with a gradual enhancement of crystallinity accompanied by significant particle growth with increasing annealing temperature, while the WO$_3$ and CuO-WO$_3$ films were more thermally stable to crystallization and particle growth. Notably, at 400$^\circ$C, the CuO--WO$_3$ films crystallized into a novel $γ$-CuWO$_4$ phase. The annealed films were further evaluated for their gas-sensing performance upon H$_2$ exposure and the obtained results were analyzed in relation to film properties and the microstructural evolution induced by annealing.

cond-mat.mtrl-sci↗