In this report, atomic force microscopy (AFM) nanolithography and electrochemical anodic oxidation using bias-assisted lithography are used to created oxide patterns on the surface of a silicon substrate. Non-contact mode imaging was conducted after the lithography process to confirm the successful fabrication of oxide patterns on the surface as well as to distinguish the surface difference between the oxide layers and silicon substrate. With only a few seconds of run time, oxide patterns as narrow as 35 nm in width were created illustrating that the bias mode in the Park Scientific SmartLitho software can be used to generate well-defined nanoscale patterns and features.

Nanoporous tungsten oxide films were synthesized by an anodic oxidation process in aqueous NaF/HF electrolytes. The tungsten films were deposited by the radio frequency magnetron sputtering method on sapphire substrates, and the anodic oxidation process was conducted in a dual-electrode reaction chamber with graphite electrode. The effects of processing parameters (anodic voltage, time, temperature, and the operation distance) on the morphology and porosity of the synthesized films were investigated experimentally. The samples were characterized by x-ray diffraction and scanning electron microscopy. The results showed that the pore diameter and porosity increased gradually with increasing anodic voltage, whereas the “wall” of the pore was subjected to electric breakdown at 60 V, and the pore diameter and porosity decreased. The pore diameter and porosity showed an early increased and later decreased state as the operation time and distance are increased. The sensitive response in the resistive method is reaction-dominated type and is exhibited as a linear relationship as a function of hydrogen gas concentration. The response toward 500 ppm hydrogen in air is up to 15.1 with a response time of 10 min at 200 °C.