In this work, we fabricated oxide on an n-type silicon substrate through local anodic oxidation (LAO) using atomic force microscopy (AFM). The resulting oxide thickness was measured and its correlation with load force, scan speed and applied voltage was analyzed. The surface oxide layer was stripped using a buffered oxide etch. Ohmic contacts were created by applying silver paste on the silicon substrate back face. LAO was performed at approximately 70% humidity. The oxide thickness increased with increasing the load force, the voltage, and reducing the scan speed. We confirmed that LAO/AFM can be used to create both lateral and, to some extent, vertical shapes and patterns, as previously shown in the literature.

Abstract: Nanoporous titanium dioxide (TiO(2)) is very attractive material for various applications due to the high surface to volume ratio. In this study, we have fabricated nanoporous TiO(2) thin films on Si by anodic oxidation. 500-nm-thick titanium (Ti) films were deposited on Si by using electron beam evaporation. Nanoporous structures in the Ti films were obtained by anodic oxidization using ethylene glycol electrolytes containing 0.3 wt% NH(4)F and 2 vol% H(2)O under an applied bias of 5 V. The diameter of nanopores in the Ti films linearly increased with anodization time and the whole Ti layer could become nanoporous after anodizing for 3 hours, resulting in vertically aligned nanotubes with the length of 200～ 300 nm and the diameter of 50～80 nm. Upon annealing at 600℃ in air, the anodized Ti films were fully crystallized to TiO(2) of rutile and anatase phases. We believe that our method to fabricate nanoporous TiO(2) films on Si is promising for applications to thin-film gas sensors and thin-film photovoltaics.