Atx g

The thickness of TiO₂ thin films were measured by spectroscopic ellipsometry (WVASE32, J.A. Woollam, Co., Inc., Lincoln, CA, USA). The deposition rate was calculated from the thickness of TiO₂ film and deposition time. The structural properties of TiO₂ thin films were investigated by using grazing incidence X-ray diffraction (GIXRD, ATX-G, Rigaku, Tokyo, Japan) at a 0.35° incidence angle over a range from 20° to 80°, X-ray photoelectron spectroscopy (XPS, AXIS-HS, Shimadzu/KRATOS, Kyoto, Japan) and Raman spectroscopy (LabRAM HR-800, Horiba Jobin Yvon, Longjumeau, France) with a 532.8 nm excitation laser. The morphologies of thin films were evaluated by atomic force microscope (AFM, Nano-R2, Pacific Nanotechnology, Santa Clara, CA, USA) and field emission scanning electron microscopy (FE-SEM, SU-8020, Hitachi, Tokyo, Japan). To confirm stability of the TiO₂ films, the adhesion between TiO₂ film and substrate was checked by ultrasonic oscillation and using adhesive tapes. All of the measurements were carried out at room temperature.

Structural analyses of the samples were conducted by using a high resolution X‐ray diffraction (HRXRD, Rigaku ATX‐G) with CuKα. A symmetric Ge[220] monochromator was used on the primary beam with a scan width and scan speed of 0.01° and 0.4° min⁻¹, respectively. Reciprocal space mapping (RSM) was performed around the (224) diffraction spots to estimate the extent of relaxation of the deposited thin films.

To adjust the film thickness, Alpha-step IQ surface profiler was used to measure the step height during the deposition, and the final device thickness was determined by transmission electron microscopy (TEM) measurements. The density of a-Si (pristine) and a-Si (densified) films were characterised by X-ray reflectometry measurement (ATX-G, Rigaku, operated at 40 kV, 250 mA), and the spectra were collected using Cu K_α x-ray source (λ = 1.54 Å) with a scan range of 0–6 degrees in 2θ. X-ray photoelectron spectra (Nexsa, ThermoFisher Scientific) on Ti, Ti-Si, and Ag-Ti-Si films were measured using a micro-focus monochromatic Al K_α X-ray source (hν = 1486.6 eV). The Ti-Si and Ag-Ti-Si films were deposited in the same procedure with the device fabrication, including the post RTA process at 350 °C for 5 min in the Ar atmosphere. The amorphous phase of a-Si (densified) and Ti_4.8%:a-Si films were characterised by X-ray diffraction measurement (Dmax2500-PC, Rigaku, operated at 40 kV, 200 mA) using glancing incident scan mode with a scan range of 1 degree and a scan speed of 2 degree/min.

Crystallinity of the fabricated thin films were investigated by grazing incidence X-ray diffraction analyses (Cu Kα₁, ATX-G, Rigaku Co.), which revealed that all oxide layers were amorphous in nature expect for NiO polycrystalline film. Cross-sectional thin-film samples for TEM observations were prepared by focused-ion-beam (FIB) micro-sampling technique, in which the multilayer structure region of the TFTs was cutout and thinned by FIB (FB-2000A, HITACHI) to obtain samples for cross-sectional observation. The cross-sectional microstructure and electron diffraction pattern of the a-WO₃ devices were examined by high-resolution TEM and STEM (JEM-ARM200F, 200 kV, JEOL Ltd.).