Relationship between electrical properties and crystallization of indium oxide thin films using ex-situ grazing-incidence wide-angle x-ray scattering

Journal Article · Thu May 25 00:00:00 EDT 2017 · Journal of Applied Physics

DOI: https://doi.org/10.1063/1.4984054 · OSTI ID:1377891

González, G. B. ^[1]; Okasinski, J. S. ^[2]; Buchholz, D. B. ^[3]; Boesso, J. ^[1]; Almer, J. D. ^[2]; Zeng, L. ^[3]; Bedzyk, M. J. ^[3]; Chang, R. P. H. ^[3]

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1. DePaul Univ., Chicago, IL (United States)
2. Argonne National Lab. (ANL), Argonne, IL (United States)
3. Northwestern Univ., Evanston, IL (United States)

Grazing-incidence, wide-angle x-ray scattering measurements were conducted on indium oxide thin films grown on silica substrates via pulsed laser deposition. Growth temperatures (T_G) in this study ranged from -50 °C to 600 °C, in order to investigate the thermal effects on the film structure and its spatial homogeneity, as well as their relationship to electrical properties. Films grown below room temperature were amorphous, while films prepared at T_G = 25 °C and above crystallized in the cubic bixbyite structure, and their crystalline fraction increased with deposition temperature. The electrical conductivity (σ) and electrical mobility (μ) were strongly enhanced at low deposition temperatures. For T_G = 25 °C and 50 °C, a strong < 100 > preferred orientation (texture) occurred, but it decreased as the deposition temperature, and consequential crystallinity, increased. Higher variations in texture coefficients and in lattice parameters were measured at the film surface compared to the interior of the film, indicating strong microstructural gradients. At low crystallinity, the in-plane lattice spacing expanded, while the out-of-plane spacing contracted, and those values merged at T_G = 400 °C, where high μ was measured. This directional difference in lattice spacing, or deviatoric strain, was linear as a function of both deposition temperature and the degree of crystallinity. The crystalline sample with T_G = 100 °C had the lowest mobility, as well as film diffraction peaks which split into doublets. The deviatoric strains from these doublet peaks differ by a factor of four, supporting the presence of both a microstructure and strain gradient in this film. More isotropic films exhibit larger l values, indicating that the microstructure directly correlates with electrical properties. Lastly, these results provide valuable insights that can help to improve the desirable properties of indium oxide, as well as other transparent conducting oxides.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States)
• Sponsoring Organization: National Science Foundation (NSF); DePaul University; USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1377891
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 20 Vol. 121; ISSN JAPIAU; ISSN 0021-8979
• Publisher: American Institute of Physics (AIP)Copyright Statement
• Country of Publication: United States
• Language: English