SnO_(2-x)薄膜非化学计量比对气敏性能的影响

Influences of Nonstoichiometric Ratio on the Gas-Sensing Properties of SnO_(2-x) Thin Films

采用反应磁控溅射法制备SnO2薄膜经常出现化学计量比的失衡问题。通过控制溅射过程中的氧分压制备不同化学计量比的SnO2-x薄膜,研究非化学计量比对薄膜结构、成分以及气敏性能的影响。XRD结果表明氧分压对材料结构和取向的影响非常显著。薄膜的O/Sn和表面化学成分通过XPS进行确定,分析发现氧分压的增加促使薄膜接近化学计量比,但表面化学吸附氧含量在0.33Pa氧分压下达到最大。气敏性能测试表明,非化学计量比主要影响薄膜表面的化学吸附氧数量,从而影响导电性和气体敏感性。氧分压对薄膜化学吸附氧的影响趋势与对气敏性能的影响趋势一致。0.33Pa氧分压下制备的薄膜拥有最多的表面吸附氧,同时对氢气的灵敏度高达45.6%。另外,在0.2-0.5Pa氧分压下制备的薄膜对氢气具有较好的选择性。

Tin dioxide thin films prepared by reactive magnetron sputtering method are always nonstoiehiometrie. The nonstoichiometric ratio of SnO2-x is controlled in the sputtering process by oxygen partial pressure. Microstructure, surface composition and gas-sensing properties are studied for the various nonstoichiometric ratio thin films. According to XRD, orientation and phase structure are influenced by oxygen partial pressure. Through testing surface composition and computing the O/Sn based on XPS data, it is found that the composition of SnO2-x thin films tends to stiochiometric and the amount of adsorbed oxygen reaches to maximum value under the 0.33Pa oxygen partial pressure. Oxygen partial pressures directly influence stiochiometric and gas sensitivity of the thin film. Actually, the main effects of nonstiochiometric on conductivity and sensitivity come from the changes of chemical adsorbed oxygen on the surface of tin dioxide thin films because of the various oxygen partial pressures in the sputtering period. The best sensitivity to hydrogen gas is 45.6% for tin dioxide thin films, which is deposited in the 0.33Pa oxygen partial pressure. The results also show that tin dioxide thin films had high selectivity to hydrogen gas when sputtering oxygen partial pressure was in the range of 0.2 to 0.5Pa.