First-Principles Study Of SnO₂ Material And Preparation Of SnO₂ Thin Film

SnO₂, which is the most extensive application of gas-sensitive material, can be used to detect all kinds of flammable, explosive and dangerous gas. In this paper, the structure and characteristic of SnO₂ were studied from theoretical and experimental aspects.SnO₂ bulk structure, oxygen vacancy, Pd-doped and SnO₂ (110) surface adsorbing CO were analyzed by first-principles that are based on density functional theory. The results showed that SnO₂ was a kind of bandgap semiconductor, Sn, O must exist covalent effect; When oxygen vacancies and Pd doping concentration in SnO₂ bulk increased, conduction band width gradually increased, the band-gap width decreased gradually, optical absorption band appeared blue shift. Nine kinds of configuration were calculated by CO adsorbing on SnO₂ stoichiometric (110) and reducing (110), it obtained two types of stable structure respectively, and by further analysising it showed that: SnO₂ material's conductivity after CO adsorbing on SnO₂ (110), the models of CO adsorbing on SnO₂ stoichiometric (110) surface were more stable than CO adsorbing on SnO₂ reducing (110) surface and the model that CO adsorbed by horizontal approach between Sn (5) and O (2) on the stoichiometric (110) surface was the most stable configuration in all of the models.Through adjusting the substrate temperature, sputtering pressure and the ratio of argon to oxygen, SnO₂ thin film which had different component and micro-structure were prepared by magnetron sputtering. The results showed that: the higher the temperature of the substrate, the better of film crystallization degree; the lower the pressure in the chamber, the easier amorphous films formed and the optimum ratio of argon to oxygen is 4:1.SnO₂ thin film samples were analyzed under different anneal temperatureby XRD and TEM, the results showed that the film crystallze at 300°C, the grain size was 8 nm, and the film's degree of crystallization and the film grain size inc- reased with increasing annealing temperature. When the temperature was 600°C, the sample had become crystal entirely and the grain size was 24 nm. The samples annealed at 500°C for different times were studied; it was found that, the degree of crystalline thin films and grain size increased with increasing annealing time.According to SnO₂ material working condition, some single sensor and multi-sensor structure were designed to meet sensitivity of testing condition.