Electrical properties of Na/Mg co-doped ZnO thin films

Conducting and transparent Na–Mg co-doped ZnO thin films were deposited on glass substrates by sol–gel method. Zn (CH3COO)2·2H2O(AR), MgCl2·6H2O(AR)) and NaCl (AR) were selected as precursors. They were dissolved in methanol to form a mixed solution with a designed doping ion concentration. Diethanolamine (HN(CH2CH2OH)2, DEA, AR) was added into the mixed solution as a stabilizer in a DEA/Zn(OAC)2 molar ratio of 1:1. The electrical properties, phase structure, and surface morphology of the films were analyzed via Hall coefficient analyses, X-ray diffraction and scanning electron microscopy, respectively. The films exhibited an obscure (002) preferential growth in all the cases. Surface morphology studies showed that an increase in the films' thickness causes an increase in the grain size. Films with 0.25 μm thickness, prepared under optimal deposition conditions followed by an annealing treatment in vacuum, showed an electrical resistivity in the level of 102 Ω cm and p-type conduction. These results make Na–Mg co-doped ZnO thin films an attractive material for transparent electrodes in thin film devices.