A hydrogen gas sensor based on platinum–titanium–oxygen (Pt–Ti–O) gate silicon-metal-insulator-semiconductor field-effect transistors (Si-MISFETs) was developed. The sensor has a unique gate structure composed of titanium and oxygen accumulated around platinum grains on top of a novel mixed layer of nanocrystalline TiOx
and superheavily oxygen-doped amorphous titanium formed on SiO2/Si
substrates. The FET hydrogen sensor shows high reliability and high sensing amplitude (