Metal oxide semiconductor(MOS)gas sensors are widely used in virtue of their advantages of low cost

high sensitivity

and good stability

but the preparation of high-quality MOS gas-sensitive films is still a challenge at present.Porous WO

3

films with high purity

high crystallinity and excellent homogeneity are successfully prepared by using a photochemical deposition(PCD)method and combining annealing process.The morphology and crystal structures of WO

3

films are characterized by scanning electron microscopy(SEM)and X-ray diffract

ion(XRD).Meanwhile

the gas sensors based on the WO

3

film are constructed

and the effects of deposition layer numbers and annealing temperature on the gas-sensitive performance of the WO

3

films are researched.Results show that all the WO

3

films-based gas sensors have outstanding selectivity to acetone.The 8 deposition layers and 300℃ annealing temperature

WO

3

film obtained at which exhibits the optimal gas-sensing performance

with high sensitivity

fast response-recovery rate

and wide working range for acetone at the optimal working temperature of 280℃.