Solid solutions based on zinc oxide for transparent electrodes

    The project aims at obtaining semiconductor solid solutions based on zinc oxide with high conductivity and transparency in the visible range of the spectrum. Transparent conducting oxides are attracted extraordinary attention lately due to the progress in the field of displays, portable electronics, organic light emitting diodes (OLED), flexible electronics , multifunctional glasses , solar panels and photovoltaic converters. Transparent conductive layers in these devices are integrated . Development of new materials need to replace the costly materials based on mixed indium tin oxide (ITO), which is characterized by relatively high crystallization temperature ( 270C ) and can be obtained , only electronic conductivity type . Solid solutions based on zinc oxide are the most promising materials for creating cheaper ( bezindievyh ) transparent conductive layers.

    During the reporting period were obtained thin films of n-type zinc oxide doped with metals of group III M = In, Ga. The technique of synthesizing thin films ZnO (M) on the rotating substrate nakapyvaniem (spin coating) solutions of the respective nitrate of 2 - methoxyethanol . First produced film doped with gallium and indium together . Film grown on inorganic and polymeric substrates precoated underlayer ZnO. The conditions for obtaining smooth multilayer coating thickness of 200 - 600nm . Systematic studies of the composition , crystal structure , microstructure and surface roughness , conductivity and optical properties in the visible range of the spectrum depending on the content of heterovalent substituents.
     Found different effects of indium and gallium on the electrical and optical properties of ZnO films . Introducing a small amount of gallium ( up to 1.2 at. % ) Leads to a significant increase in the conductivity of zinc oxide films , and increased transparency in the visible spectrum . Introduction of indium in a concentration of up to 10 at. % ) Leads to a monotonic decrease of the resistance films ZnO (In), however, at high concentrations of indium optical transmittance of the films in the visible range deteriorate. The difference in the effect of heterovalent substituents on the electrical properties of ZnO films may be due to effective ionic radii of impurities determining the ratio of donor and acceptor defects. Important is the opposite effect of gallium and indium on the mobility of electrons in the material , as well as possible on the surface segregation of zinc oxide grains and Ga- In- containing X-ray amorphous phases. Detected exciton absorption band due to the formation of more perfect crystalline structure of the doped films , the dependence of the energy content of the exciton peak Heterovalent deputy.
    The films are transparent in the visible range , the undoped ZnO for the wavelength range 400 - 800 nm the average transmittance value of 89 %. Introducing a small amount of gallium ( 0.5 - 2 at. % ) Increases the average value of the transmission to 95 %. Thin films co-doped with gallium and indium ( 0.7 atom % In) characterized by a maximum value of 97 % transmittance at wavelengths of 400-800 nm.

KEYWORDS
    Zinc oxide transparent electrodes , a solid solution thin film , conductivity , optical transmission , sol -gel , laser ablation