Features of the hopping conductivity in gallium and cobalt doped ZnO thin films

27th International Conference on Low Temperature Physics

Kytin, V.G.^1 ; Reukova, O.V.^1 ; Kulbachinskii, V.A.^1 ; Burova, L.I.^2 ; Kaul, A.R.^2 ; Ulyashin, A.G.^3

Physics Faculty, M.V. Lomonosov Moscow State University, Moscow

119991, Russia^1

Chemistry Department, M.V. Lomonosov Moscow State University, Moscow

119991, Russia^2

SINTEF Materials and Chemistry, Forskingsveien 1, Blindern, OSLO

0314, Norway^3

关键词: Density of localized state;    Magneto transport properties;    Metal organic chemical vapour depositions;    Monocrystalline substrates;    Negative magneto-resistance;    Positive magnetoresistance;    Structural disorders;    Temperature dependencies;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/568/5/052015/pdf
DOI  :  10.1088/1742-6596/568/5/052015

来源: IOP

【 摘 要 】

The effect of Ga and Co doping on the hopping transport of electrons in ZnO films was studied. All investigated films were deposited on monocrystalline substrates by water assisted metal organic chemical vapour deposition method. Temperature dependencies of the resistivity of all films obeyed the Mott's law at low temperatures. Both positive and negative magnetoresistance were observed in the temperature range of the Mott's law. The values of the localization length obtained from magneto transport data for ZnO and ZnO:Ga films are larger than the effective Bohr radii of a shallow donor state and are independent on the Ga content. These observations point to the localization of electrons in the random potential originating from the structural disorder. In Co doped ZnO films large positive magnetoresistance was observed in low magnetic fields at low temperatures. The value of positive magnetoresistance increases with an increase of Co content and decrease of temperature. Observed magneto transport properties of Co-doped films were interpreted by the decrease of electron hopping probability due to decrease of the density of localized states in magnetic field.