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.

Hydrophilic Antireflection and Antidust Silica Coatings

“…The stacking layers of SiO 2 /TiO 2 have also been investigated and have resulted in higher transmission, where titania nanoparticles resulted in a higher refractive index (n = 2.45) beyond the optimum value. 19 However, although such layers demonstrated improved optical properties due to a minimal reflectance value, they were not qualified to be used as self-cleaning assemblies.…”

“…In addition, a report by Kintaka and co-workers studied the usage of methyl tri-ethoxysilane (MTES) and tri-methylethoxysilane (TMES) as precursors to developing hydrophobic AR layers, where the CA increases from 22 to 108°. The stacking layers of SiO 2 /TiO 2 have also been investigated and have resulted in higher transmission, where titania nanoparticles resulted in a higher refractive index ( n = 2.45) beyond the optimum value . However, although such layers demonstrated improved optical properties due to a minimal reflectance value, they were not qualified to be used as self-cleaning assemblies.…”

“…A silica thin film has the properties to show simultaneously high optical transparency and low refractive index values, suitable to be used as optical films from the near-ultraviolet to the near-infrared spectral range. − This silicon oxide layer suppresses any parasitic light absorption in the visible range due to its suitable optical band gap and transmission range. − Also, low refractive index values allow these layers to be coupled with high-refractive-index materials for antireflection coating applications by minimizing the total light reflectance. − In addition, due to their high optical transparency, high hydrophobicity property, and the uniformity of their surface, silica layers are extensively used in various industrial and general-purpose applications including flexible displays, optics, bioengineering, ophthalmic, and energy generation. − ,− …”

“…Many techniques have been already employed to grow silica films, including electron beam evaporation, ion-assisted deposition, ion beam sputtering, magnetron sputtering (MS), sol–gel, and atomic layer deposition. − Among all of these techniques, magnetron sputtering (MS) demonstrated the best deposition competency due to the fine control over the growth parameters, film-uniformity, homogeneity, the low density of pinholes to resist defects, and stable optical properties. ,− Hence, nowadays, MS has become a state-of-the-art technique to grow pristine silica films even with large-scale capabilities. Moreover, having the ability to perform the reactive growth of these films under oxygen or any other reactive atmosphere help in controlling the film’s stoichiometry.…”

Optical Properties in Mid-Infrared Range of Silicon Oxide Thin Films with Different Stoichiometries

“…Thin-film SiO 2 is a material that has been extensively studied and is widely used in numerous applications, such as materials with a low refractive index, a barrier for thermal diffusion, and for improving adhesion or enhancing mechanical strength, among many others [16][17][18][19][20][21][22][23][24]. The properties of SiO 2 and SiO x thin films have also been studied in the mid-infrared range [25][26][27], a spectral region that is of great interest in topics related to blackbody radiation at room temperature [28] or in astronomy, as well as in current research topics such as "epsilon near zero" metamaterials or the fabrication of perfect anti-reflective coatings at specific wavelengths [29][30][31][32][33][34].…”