New technology of metal oxide thin film preparation for chemical sensor application

The reduction of grain size in metal oxide films is one of the key factors to enhance the gas sensing properties of semiconductor layers. The basic idea introduced here is to create thin metal oxide films with small grain size by using a special regime of rf sputtering from either metallic or metal oxide targets. The regime includes the deposition of thin films with one or several interruptions of the sputtering process. The idea has been checked by preparing WO3 thin films using reactive rf sputtering from a pure tungsten target. Four types of films were prepared. For the first type a non-interrupted sputtering was used. In the deposition of films type 2, 3 and 4, the sputtering process was interrupted once, two and three times, respectively. It was found that the thickness of the WO3 films and the sensing properties of WO3 based sensors heavily depend on the number of interruptions during the deposition process.