Change of electronic structure of ultrathin film of indium tin oxide by “In situ” Ar+ ion non-reactive successive etching process

"In situ" argon (Ar⁺) ion non-reactive successive sputtering/etching process was used to produce ultrathin films of indium tin oxide nanomaterial. In each sputter/etch-cycle (τ_etch = 300s), x-ray photoelectron spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UV PES) were measured and studied their change of electronic/bonding/atomic structure, density-of-states (DOS), valence band maximum (VBM), and work functions of the ultrathin films of indium-tin-oxide nanomaterial. During Ar⁺-ion non-reactive successive sputtering/etching process ((τ_etch = 0-1800 s) the thicknesses are reducing from 100 nm (ITO) ≈ 2.0 nm (ultrathin films of indium-tin-oxide). These results were further revealed with the "ex-situ" HR-SEM, HR-TEM, AFM, XRD, Raman, and x-ray absorption near edge structure (XANES) spectroscopy measurements, where a small shift of the Raman mode (A_1g) peak with reduced intensity and XANES edge-shift with change in line shape/intensities further confirmed the formation of ultrathin films of indium-tin-oxide nanomaterial. The SEM/TEM/AFM of Ar⁺-ion sputtered/etched (τ_etch = 1800 s) of these films are considered as an alternative technique to make ultrathin films of indium-tin-oxide nanomaterial for the fabrication of future electronic/optoelectronic/photovoltaic devices.