Preparation And Optoelectronic Properties Of ZnO Films

Zinc oxide (ZnO) film has been widely used in transparent conducting films and gas sensors because of its unique optoelectronic properties. The properties of ZnO film are strongly dependent on preparation techniques which include substrate temperature, oxygen partial pressures (OPP), annealing process. In the dissertation, ZnO films have been prepared by magnetron sputtering and E-beam evaporation methods. The main contents include:Firstly, ZnO films with different OPP were deposited on quartz substrates by RF magnetron sputtering. The surface roughness and carrier concentration decrease as OPP increases, but the carrier mobility and resistivity increase. The average transmittance in visible spectra region of all samples is higher than 83%. The refractive index increases, extinction coefficient and optical band gap decrease as the increase of OPP.Secondly, Ag doped ZnO (ZnO:Ag) thin films were deposited on n-Si (100) substrates by E-beam evaporation technique. The films were annealed at temperature between 500 and 800℃for 4 hours in low oxygen pressure. When the annealing temperature increases from 500℃to 800℃, the crystalline size increases from 12.37 nm to 32.36 nm, ultraviolet emission peak shifts to short wavelength, the carrier concentration increases and resistivity decreases.Thirdly, ZnO films were deposited on p-Si (111) substrates which had been coated a S1O2 layer to fabricate n-ZnO/SiO2/p-Si heterojunctions.Ⅰ-Ⅴcurves show all the heterojunctions exhibit rectification characteristics and changed obviously under the light. The heterojunctions with no SiO2 layer has a better photoconductive with sensitivity of 1.531. Under reversed bias, the intensity of potential barrier increases with the increase of SiO2 thickness, and potential barrier has efficiently blocked electron tunneling which make the heterojuction has a better rectification characteristic.