SnO2 thin films and La-doped SnO2 thin films are prepared by two-step vacuum thermal evaporation on glass substrates.The effect of oxidation

heat-treatment and doping content of La on the structure

sensitive characteristics of SnO2 films is studied.The results show that SnO2 thin films are n-type rutile structure by the heat-treatment of 45 min in O2 at temperature of 500 ℃.The proper doping of La can mend the crystal status of the SnO2 films

for which the choice and sensitive characteristics for gases can be improved obviously after doping.When gas volume fraction is 1×10-2

the sensitivity of SnO2 thin films La-doped（5 %） to ethanol is 12

whereas that can approach to 14 for La-doped（3 %）.