Study On The Synthesis And Properties Of Semiconductor Oxide Thin Films

Semiconductor materials refer to materials that possess conductivity between those ofmetals and insulators, with room temperature conductivity σ ranging from10-8to105S·m-1.The electrical properties of semiconductors are usually affected by the ambient atmospheresuch as light intensity, electric field strength, temperature, humidity and so on. Due to theirimportant roles, semiconductor materials have become the pillar industry in our modernsociety and are called as “industrial food”.Oxide semiconductor means oxide possessing semiconductor characteristics. The electricalcharacteristics of oxide semiconductors are usually affected by the oxygen partial pressure inthe atmosphere. If the conductivity of the oxide semiconductor will increase at the presence ofthe oxidative atmosphere, it is called oxidation-type semiconductor, or p-type semiconductor;whereas, if the conductivity of the oxide semiconductor will increase with the reductiveatmosphere, it is called reduction-type semiconductor, or n-type semiconductor.In this article we report the preparation and characterization of three kind of oxidesemiconductor materials: SnO2thin films; TiO2thin films and In2O3particles. Specifically, itcontains:1Tin oxide thin films: synthesis and gas sensing propertiesHigh quality of SnO2thin films on glass substrates were prepared solvothermally from theseed films fabricated by sol-gel technique. The synthetic procedure has the merit of simplicityand low cost. It reveals that using SDBS as the surfactant can significantly improve the filmquality during the solvothermal reaction. When used as gas sensors, the SnO2SDBS-filmsshow good gas sensing performance to NO2gas at mild test conditions such as roomtemperature, ambient pressure, and dry air background, and a detection limit of about0.5ppmis achieved. The surfactant-free-films show a little bit inferior discrimination ability to differentconcentrations of NO2gases although their responses to sample gases are quite high, which isascribed to their easiness of reaching the saturated adsorption due to the SnO2crystals’ cleansurfaces as well as its higher surface to volume ratio. The SnO2films also exhibit good sensingselectivity. When exposed to5ppm of CO gas, the sensors show no obvious responses. 2Preparation and properties of titanium dioxide thin filmsTitanium dioxide films with high quality were prepared by using sol-gel method, in whichthe effects of sol conditions and film fabrication techniques on the film quality wereinvestigated in details. The spin coating technique was shown to be more effective inobtaining high quality of films than dip coating method does. For fabricating multilayer films,it showed that the film fabrication strategy of “coating-drying-heattreatment……coating-drying-heat treatment” is much better than that of“coating-drying……coating-drying-heat treatment”. Additionally, experiments based onelement doping showed that the strontium-doped titanium dioxide thin films revealed muchenhanced photocatalysis performance compared with those of the un-doped titanium dioxide.3Preparation of indium oxide particles on Si substrate by chemical vapor deposition (CVD)methodMicron/nano scaled In2O3particles were grown on Si substrates by using CVD method.Keeping the oxygen flow rate of6sccm, indium oxide particles with regular octahedron andtruncated octahedron morphologies were synthesized. The growth mechanism of theseparticles was proposed based on the results of the experiments: on on hand, the morphologiesof the crystals were determined by the growth rates of different low-energy crystallographicplanes; on the other hand, the mobility and mean free path of absorbed reagent species usuallydetermine the growth behavior of the crystals. The octahedral crystals were considered to beformed under dynamic equilibrium with the growth rates of crystallographic planesproportional to the surface energy, whereas, non-dynamic equilibrium and various structuraldefects promote the growth of imperfect cubes.