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应用基于密度泛函理论(DFT)的第一性原理,并借助Materials Studio软件中Castep模块建立了CO与SnO_2薄膜(110)面的吸附模型,最终确定了Pd掺杂的与纯净的SnO_2(110)面的最佳吸附位置分别为O_(2C)和Sn_(5C),吸附能分别为-1.842 5 eV和-0.533 3 eV。在此基础上,通过分析吸附体系电子态密度(DOS)及差分电荷密度的变化,阐明了SnO_2基CO气体传感器敏感膜的微观电阻变化机理及利用Pd掺杂能够改善气敏性能的原因。最后实验表明,Pd掺杂后SnO_2薄膜最佳工作温度由275℃降至200℃,灵敏度提高到30.1,验证了理论分析的结果。
The first principle of density functional theory (DFT) was applied and the adsorption model of the (110) plane of CO and SnO_2 thin films was established by means of Castep module in Materials Studio software. Finally, the Pd-doped and pure SnO_2 (110 ) Are O_ (2C) and Sn_ (5C), respectively, and their adsorption energies are -1.842 5 eV and -0.533 3 eV, respectively. On this basis, the change mechanism of DOS and differential charge density of adsorbed system is analyzed, and the mechanism of microscopic resistance change of SnO_2-based CO gas sensor sensitive membrane and the reason of using Pd doping to improve gas sensitivity are illustrated. The final experiment shows that the optimal working temperature of SnO_2 film after Pd doping is reduced from 275 ℃ to 200 ℃ and the sensitivity is increased to 30.1, which verifies the theoretical analysis results.