Abstract
The unique response of amorphous ionic oxides to changes in oxygen stoichiometry is investigated using computationally intensive ab initio molecular dynamics simulations, comprehensive structural analysis, and hybrid density-functional calculations for the oxygen defect formation energy and electronic properties of amorphous In2O3-x with x = 0-0.185. In marked contrast to nonstoichiometric crystalline nanocomposites with clusters of metallic inclusions inside an insulating matrix, the lack of oxygen in amorphous indium oxide is distributed between a large fraction of undercoordinated In atoms, leading to an extended shallow state for x < 0.037, a variety of weakly and strongly localized states for 0.074 < x < 0.148, and a percolation-like network of single-atom chains of metallic In-In bonds for x > 0.185. The calculated carrier concentration increases from 3.3 x 1020cm-3 at x = 0.037 to 6.6 x 1020 cm-3 at x=0.074 and decreases only slightly at lower oxygen content. At the same time, the density of deep defects located between 1 and 2.5 eV below the Fermi level increases from 0.4 x 1021 cm-3 at x = 0.074 to 2.2 x 1021 cm-3 at x = 0.185. The wide range of localized gap states associated with various spatial distributions and individual structural characteristics of undercoordinated In is passivated by hydrogen that helps enhance electron velocity from 7.6 x 104 to 9.7 x 104 m/s and restore optical transparency within the visible range; H doping is also expected to improve the material's stability under thermal and bias stress.
Recommended Citation
J. E. Medvedeva et al., "Metallic Networks and Hydrogen Compensation in Highly Nonstoichiometric Amorphous In₂O₃₋ₓ," Physical Review Materials, vol. 6, no. 2, article no. 25601, American Physical Society (APS), Feb 2022.
The definitive version is available at https://doi.org/10.1103/PhysRevMaterials.6.025601
Department(s)
Physics
International Standard Serial Number (ISSN)
2475-9953
Document Type
Article - Journal
Document Version
Final Version
File Type
text
Language(s)
English
Rights
© 2022 American Physical Society (APS), All rights reserved.
Publication Date
01 Feb 2022
Comments
The authors acknowledge the support from the National Science Foundation (NSF) DMREF Grants No. DMR-1729779 and No. DMR-1842467. The computational resources were provided by Missouri S&T and NSF-MRI Grant No. OAC-1919789.