Fluoride Doping in Crystalline and Amorphous Indium Oxide Semiconductors


In this contribution, the structural and electronic effects of fluoride doping in both crystalline and amorphous indium oxides are investigated by both experimental and theoretical techniques. Pristine crystalline and amorphous fluoride-doped indium oxide (F:In-O) phases were prepared by solution-based combustion synthesis and sol-gel techniques, respectively. The chemical composition, environment, and solid-state microstructure of these materials were extensively studied with a wide array of state-of-The-Art techniques such as UV-vis, X-ray photoelectron spectroscopy, grazing incidence X-ray diffraction, 19F and 115In solid-state NMR, high-resolution transmission electron microscopy (HR-TEM), and extended X-ray absorption fine structure (EXAFS) as well as by density functional theory (DFT) computation combined with MD simulations. Interestingly, the UV-vis data reveal that while the band gap increases upon F-doping in the crystalline phase, it decreases in the amorphous phase. The 19F solid-state NMR data indicate that upon fluorination, the InO3F3 environment predominates in the crystalline oxide phase, whereas the InO4F2 environment is predominant in the amorphous oxide phase. The HR-TEM data indicate that fluoride doping inhibits crystallization in both crystalline and amorphous In-O phases, a result supported by the 115In solid-state NMR, EXAFS, and DFT-MD simulation data. Thus, this study establishes fluoride as a versatile anionic agent to induce disorder in both crystalline and amorphous indium oxide matrices, while modifying the electronic properties of both, but in dissimilar ways.




The authors thank the Northwestern U. MRSEC grant NSF-DMR 1720139 for support of this research. J.E.M. thanks NSF-DMREF grants DMR-1729779 and DMR-1842467 for support and NSF-MRI grant OAC-1919789 for computational facilities.

International Standard Serial Number (ISSN)

1520-5002; 0897-4756

Document Type

Article - Journal

Document Version


File Type





© 2022 American Chemical Society (ACS), All rights reserved.

Publication Date

24 Mar 2022