ITO/SiO2/ITO Structure on a Sapphire Substrate Using the Oxidation of Ultra-Thin Si Films as an Insulating Layer for One-Glass-Solution Capacitive Touch-Screen Panels

Abstract

The SiO2 generated by low-temperature oxidation of ultra-thin metallic silicon (thickness = 50 nm) film was evaluated for implementation in one-glass-solution capacitive touch-screen panels (OGS-TSPs) on sapphire-based substrates. Our results show that the silicon films oxidized at 823 K exhibited the highest visible transmittance about 91% at 550 nm, compared to ~72% transmittance of the as-deposited silicon films which were deposited at room temperature. Additionally, the annealed films exhibited a more uniform, dense, and smooth surface microstructure than that of the as-deposited Si films. X-ray photoelectron spectroscopy (XPS) results revealed that the low-temperature oxidation of Si films at 823 K yielded SiO2. Furthermore, when the insulating SiO2 film obtained by low-temperature oxidation was sandwiched between two indium tin oxide (ITO) layers (ITO/SiO2/ITO) on a sapphire substrate, the SiO2 film resulted in the dielectric strength of approximately 3 MV/cm. In addition, the highest optical transmittance obtained by the ITO/SiO2/ITO films is about 88.3%. The change in capacitance of the ITO/SiO2/ITO structure was approximately 3.2 pF, which indicates the possibility of implementation in capacitive touch-screen panel devices.