Electron-vacancy scattering in SrNbO\(_3\) and SrTiO\(_3\): A DFT-NEGF study

• Published in: arXiv.org
• Main Authors: Rosendal, Victor, Pryds, Nini, Dirch Hjorth Petersen, Brandbyge, Mads
• Format: Paper
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 11.01.2024
• Subjects: Density functional theory; Electron transport; Functionals; Green's functions; Lattice vacancies; Perovskites; Scattering cross sections; Thin films; Unit cell
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2401.06039

Oxygen vacancies are often attributed to changes in the electronic transport for perovskite oxide materials (ABO\(_3\)). Here, we use density functional theory (DFT) coupled with non-equilibrium Green's functions (NEGF) to systematically investigate the influence of O vacancies and also A and B-site vacancies, on the electronic transport as characterised by a scattering cross-section. We consider SrNbO\(_3\) and n-type SrTiO\(_3\) and contrast results for bulk and thin film (slab) geometries. By varying the electron doping in SrTiO\(_3\) we get insight into how the electron-vacancy scattering vary for different experimental conditions. We observe a significant increase in the scattering cross-section (in units of square-lattice parameter, \(a^2\)) from ca. \(0.5-2.5a^2\) per vacancy in SrNbO\(_3\) and heavily doped SrTiO\(_3\) to more than \(9a^2\) in SrTiO\(_3\) with 0.02 free carriers per unit cell. Furthermore, the scattering strength of O vacancies is enhanced in TiO\(_2\) terminated surfaces by more than 6 times in lowly doped SrTiO\(_3\) compared to other locations in slabs and bulk systems. Interestingly, we also find that Sr vacancies go from being negligible scattering centers in SrNbO\(_3\) and heavily doped SrTiO\(_3\), to having a large scattering cross-section in weakly doped SrTiO\(_3\). We therefore conclude that the electron-vacancy scattering in these systems is sensitive to the combination of electron concentration and vacancy location.