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 Ionn/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.
- Atomic force microscopy,
- Calculations,
- Carrier transport,
- Combustion synthesis,
- Crystal atomic structure,
- Density functional theory,
- Electronic structure,
- Extended X ray absorption fine structure spectroscopy,
- Fluorine compounds,
- Metals,
- Molecular dynamics,
- Morphology,
- MOS devices,
- Negative ions,
- Optoelectronic devices,
- Oxide semiconductors,
- Semiconducting indium,
- Semiconductor doping,
- Silicon on insulator technology,
- Synthesis (chemical),
- Thin film transistors,
- Thin films,
- Transport properties,
- X ray absorption,
- X ray photoelectron spectroscopy, Ab initio molecular dynamics simulation,
- Electronic structure calculations,
- Extended X-ray absorption fine structures,
- Grazing incidence X-ray diffraction,
- Metal oxide semiconductor,
- Opto-electronic materials,
- Optoelectronic properties,
- Thin-film transistor (TFTs), Indium compounds
Available at: http://works.bepress.com/julia-medvedeva/79/