The Optical Properties Of In-N Co-Doped ZnO Thin Films By Sol-Gel Spin-Coating Method

Among various transparent conductive oxides such as zinc oxide(ZnO),indium tin oxide(ITO),and fluorine-doped tin oxide(FTO),ZnO has received a great deal of attention because it has a wide band gap(3.37 eV),high excitation binding energy(60 meV),and low production cost.Currently,ZnO thin film has been used in diverse applications such as thin film transistors(TFT),light-emitting devices(LED),optoelectronic devices,and solar cells.In this thesis,unintentionally doped ZnO thin films,In-doped ZnO thin films and In-N co-doped ZnO thin films were prepared on glass substrates by sol-gel spin coating method.The lattice structure,surface morphology,optical transmittance and optical band gap of the films were investigated by X-ray diffraction(XRD),scanning electron microscopy(SEM),and ultraviolet-visible spectrophotometer(UV-Vis).The main contents and results are as follows:(1)Different sol concentrations have a great influence on the crystallization properties of unintentionally doped ZnO thin films.When the sol concentration is 0.4 mol/L,the film has the best c-axis orientation,the highest crystallinity,and the average transmittance in the visible range is 80%.(2)The crystallinity of the ZnO thin film decreases with the In doping,and the(002)diffraction peak of the thin film shifts to the small angle.The surface morphology of the thin film changes significantly,and even the adhesion phenomenon occurs.However,the transmittance of the film has been significantly improved,reaching about 90%,and the absorption edge of the transmission curve has a blue shift,which corresponds to an increase of the forbidden band width.(3)With the increase of N doping amount,the crystallinity of In-N co-doped ZnO thin film has been improved significantly.When the N doping amount is 8.0 at%,the(002)diffraction peak intensity of the film is the highest,the crystallinity is the best.The surface of the film has uniform grain size and dense arrangement,the transmittance is about 90%,and the band gap is slightly reduced.