Control of Electron Transport in Quasi-2D Layered ZnO and CuO Films via Surface Modification

Abstract

Quasi-2D metal oxide films, particularly ZnO and CuO, are promising candidates for solid-state gas sensors, where the operating principle relies on surface-modulated conductivity. However, theoretical modeling of such systems faces two fundamental challenges: monolayer models significantly overestimate the bandgap (up to 4.4 eV for ZnO and 3 eV for CuO), and standard SCC-DFTB parameter sets for copper oxide lead to unphysical lattice collapse during geometry optimization.
In this work, we present a combined theoretical approach to overcome these limitations. For ZnO(11-20), a layer-by-layer growth methodology is proposed. We demonstrate that a four-layer atomic model (24 Å thick) reproduces the bulk bandgap of 3.6 eV and stabilizes the Fermi level at −2.65 eV. Using the NEGF formalism and Landauer-Büttiker theory, we simulate the physical adsorption of organic molecules (alcohols and ketones). The results reveal a resistance decrease of 0.4–29% due to charge transfer from donor molecules to the n-type surface. Notably, ketones produce a stronger response than alcohols, driven by charge delocalization across the surface rather than the magnitude of charge transfer.
For CuO(111), we developed a modified Slater-Koster parameterization using the TANGO package, improving geometric accuracy by a factor of four. Transport calculations show that oxygen vacancies reduce resistance by four orders of magnitude via surface metallization, while molecular O₂ adsorption decreases resistance by eight orders of magnitude due to substantial charge transfer (−1.89 e).
These results provide a reliable theoretical foundation for designing highly sensitive metal-oxide nanosensors.

Speaker

Pavel Kolesnichenko
Saratov State University
Russian Federation

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