arXiv subjects

Jemal Yimer Damte

Publications and source records attributed to Jemal Yimer Damte.

6 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

First Principles Investigation of Gas Adsorption on Bilayer Transition Metal Dichalcogenides for Sensing Toxic Gases

Transition metal dichalcogenides have shown great promise in the field of gas sensing due to their high catalytic activity and unique electronic properties. They can effectively interact with various gas molecules, making them suitable materials for high performance gas sensors. In this work, we have studied the sensing properties of nitrogen containing gases on different heterostructures using density functional studies. The result shows that NH3 and NOx exhibit weak electronic interactions with MoS/WTe and MoTe/WS heterostructures and strong electronic interactions are observed between NH3 and NOx molecules with MoS/IrO and MoS/TiO heterostructures.

physics.app-ph↗

arXiv2024

Formation of C1 oxygenates by Activation of Methane on B, N Co-doped Graphene Surface Decorated by Oxygen Pre-covered Ir13 Cluster: A First Principles Study

We employ density functional theory (DFT) to investigate the adsorption and dehydrogenation of methane on the BNG-Ir13 cluster at both low and high oxygen coverage. The DFT calculations show that the low-oxygen-coverage BNG-Ir13 cluster (BNG-Ir13O cluster) forms methanol and formaldehyde with a lower activation energy barrier compared to the high-oxygen-coverage BNG Ir13 cluster. Furthermore, the results reveal that the BNG-Ir13 cluster with low oxygen coverage has a higher methane adsorption energy and a lower activation energy barrier for methane dissociation compared to the high-oxygen-coverage BNG-Ir13 cluster. Quantitatively, the methane adsorption energy on the low-oxygen-coverage BNG-Ir13 cluster is -0.44 eV, and the second dehydrogenation of methane is the rate-determining step with an energy barrier of 1.24 eV, in both cases lower numbers than those observed for the high-oxygen-coverage BNG-Ir13 cluster.

physics.app-ph↗

arXiv2024

Tribo-piezoelectric Nanogenerators for Energy Harvesting: a first-principles study

Two-dimensional transition metal dichalcogenides (TMDs) are highly promising candidates for various applications due to their unique electrical, optical, mechanical, and chemical properties. Furthermore, heterostructures consisting of TMDs with metals, oxides, and conductive materials have attracted significant research interest due to their exceptional electronic properties. In this study, we utilized density functional theory to investigate those electronic and transport properties, which are relevant for the application of tribo-piezoelectricity in creating novel nanogenerators: an interdisciplinary approach with promising implications. The results of the study demonstrate that the enhancement of charge transfer between layers and the orbital contribution to the Fermi level under applied strain in MoS/IrO, MoS/TiO, MoS/WTe, and MoTe/WS heterostructures is noteworthy. Additionally, non-equilibrium Green's function calculations of electron transport properties provide valuable insights into the behavior of these materials under different conditions. While MoS/IrO and MoS/TiO hetero-bilayers are unsuitable due to their tendency to exhibit large current flow with increasing voltage, others like MoS/WTe and MoTe/WS hetero bilayers show promise due to their ability to prevent voltage drop. The presented innovative concept of utilizing compressive strain of TMD bilayers to generate a tribo-piezoelectric effect for nanogenerators has a potential to contribute to the development of efficient and sustainable energy harvesting devices.

cond-mat.mtrl-sci↗