“…Various oxide semiconductor films such as SnO 2 , (1)(2)(3)(4)(5) WO 3 , (6)(7)(8)(9) TiO 2 , (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) MoO 3 , (23,24) NiO, (25,26) In 2 O 3 , (27,28) and ZnO (29,30) have been studied as gas-sensing materials and they demonstrated good sensing properties for detecting target gases such as NO x , O 3 , NH 3 , CO, H 2 , H 2 S, and CH 4 . Of these oxide semiconductor films, TiO 2 , an n-type semiconductor, has recently attracted much attention because of its high durability, high chemical stability in hostile environments, and thermal stability at high temperature.…”