Structure-Charge Transport Relationships in Fluoride-Doped Amorphous Semiconducting Indium Oxide: Combined Experimental and Theoretical Analysis

Aritra Sil, Laleh Avazpour, Elise A. Goldfine, Qing Ma, Wei Huang, Binghao Wang, Michael J. Bedzyk*, Julia E. Medvedeva, Antonio Facchetti, Tobin J. Marks

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

Anion doping of transparent amorphous metal oxide (a-MO) semiconductors is virtually unexplored but offers the possibility of creating unique optoelectronic materials owing to the chemical tuning, modified crystal structures, and unusual charge-transport properties that added anions may impart. We report here the effects of fluoride (F-) doping by combustion synthesis, in an archetypical metal oxide semiconductor, indium oxide (In-O). Optimized fluoride-doped In-O (F:In-O) thin films are characterized in depth by grazing incidence X-ray diffraction, X-ray reflectivity, atomic force microscopy, X-ray photoelectron spectroscopy, and extended X-ray absorption fine structure (EXAFS). Charge-transport properties are investigated in thin-film transistors (TFTs), revealing that increasing fluoride content (0.0 → 1.57 atom %) slightly lowers the on-current (Ion) and electron mobility due to scattering from loosely bound F- centers but enhances important TFT performance parameters such as the Ion/Ioff ratio, subthreshold swing, and bias stress stability, yielding superior TFT switching versus undoped In-O. These results are convincingly explained by ab initio molecular dynamics simulations and density functional theory electronic structure calculations. Combined with the EXAFS data, the experimental and theoretical results show that F- hinders crystallization by enhancing the local and medium-range disorder, promotes a uniform film morphology, and favors the formation of deeper, more localized trap states as compared to F--free In-O. These data also show that the local organization and electronic structure of amorphous F--doped oxide semiconductors are significantly different from those of F--doped crystalline oxide semiconductors and suggest new avenues to further modify a-MOs for enhanced optoelectronic properties.

Original languageEnglish (US)
Pages (from-to)805-820
Number of pages16
JournalChemistry of Materials
Volume32
Issue number2
DOIs
StatePublished - Jan 28 2020

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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