Surface engineering using compounds of titanium nanocoatings for silicon based optical devices

摘要

Most silicon based detectors are sensitive predominantly in the visible region. To extend their sensitivity further into theUV and IR regions, surface modification techniques can be employed. In addition, there is always a need for biocompatible,eco-friendly, and cost effective devices for bio-medical applications. Therefore, devices fabricated usingsilicon and titanium can enable the fabrication of affordable health care devices. Another critical factor that plays a majorrole in controlling the device performance is its surface wettability. Tuning the surface energy and thus its wettability canimprove the stability, passivation, self-cleaning, and anti-aging properties of device surfaces. In this paper, we present amethod for tuning the surface wettability with enhanced optical absorption in the UV-Vis-NIR regions. We optimize thetitanium coatings on silicon substrates and demonstrate how the controlled deposition of film thickness and annealingtemperature or time can affect the self-cleaning behavior and light localization with anti-reflection properties of surfaces.We take the combined advantage of the anti-reflective properties of anatase or rutile phases of oxides of titanium (TiOx)and the nature of opto-semiconductor Schottky barrier Ti-O-Si formed at the titanium and silicon interface for theimproved absorption in a wide spectral range of radiation ranging from 200 nm (UV) to 3000 nm (short-wavelengthinfrared) wavelengths. An average optical reflectance tuned to less than 10% and absorbance greater than 70% can beobtained. Further, these coatings act as a protective encapsulation by possessing a hydrophobic surface with watercontact angles > 100°.