Abstract
Indium-based amorphous metal oxides (AMOs) are important materials that enable a wide range of electronic and optoelectronic applications. The metal cations that substitute for In are known to effectively tune the material properties as well as to retain the desirable amorphous state when subjected to high operating temperatures. While much attention focuses on property tuning, there is less focus on those fundamental factors that enhance thermal stability. Hence, in this paper, we employ in situ X-ray scattering and ab initio molecular dynamics (MD) to systematically study the effects of secondary cations on the crystallization process. A series of amorphous (In1-xMx)2O3 thin films (M = Sn, Zn, and Ga; x = 5, 10, 20, and 30%) are grown by pulsed laser deposition (PLD) under identical deposition conditions. The films are then annealed isochronally, and the degree of crystallinity, crystallization temperature (Tc), and crystallization time (τc) are determined by a quantitative analysis of the time-evolved X-ray scattering patterns. All doped films have a Tc higher than the corresponding undoped films, and significantly higher Tc values (>400 °C) are found at the higher degrees of Zn and Ga substitution (20 and 30%). For the same level of substitution, Tc increases in the order Sn > Zn > Ga, suggesting increasing crystallization barriers and local structural disorder. All crystallized films are in the common cubic phase except for IZO-20%, where an additional rhombohedral phase is observed throughout the crystallization process. The pole figure analysis reveals the detailed preferred orientations buried in postannealed crystalline films. Complementary ab initio molecular dynamics (MD) simulations of the as-deposited AMOs provide an informative theoretical perspective. The medium-range structures characterized by the value and variance of effective coordination numbers around metal and oxygen atoms are found to play an important role in explaining the observed crystallization dynamics in these oxides.
Recommended Citation
L. Zeng et al., "Thermal Stability of Amorphous Metal Oxides: The Interplay of Secondary Cations, Degree of Substitution, and Local Structure," Chemistry of Materials, vol. 36, no. 12, pp. 5965 - 5975, American Chemical Society, Jun 2024.
The definitive version is available at https://doi.org/10.1021/acs.chemmater.4c00351
Department(s)
Physics
International Standard Serial Number (ISSN)
1520-5002; 0897-4756
Document Type
Article - Journal
Document Version
Citation
File Type
text
Language(s)
English
Rights
© 2024 American Chemical Society, All rights reserved.
Publication Date
25 Jun 2024
Comments
Northwestern University, Grant OAC-1919789