Electrical properties of ZnO thin films deposited by pulsed laser deposition

Structural and electronic transport properties of polycrystalline ZnO thin films, prepared by pulsed laser deposition, have been investigated. The films were deposited on glass and Si3N4/Si substrates using O-2 and N-2 atmospheres. X-ray analysis revealed preferential c-axis orientation perpendicular to the sample substrate. Films deposited under relatively high 02 pressure were highly resistive. However, the conductivity a increased while the films were irradiated with ultraviolet light, showing an Arrhenius (In sigma proportional to T-1) dependence as a function of temperature. The ZnO film deposited in N2 atmosphere exhibited at room temperature a resistivity similar to 1 Omega cm, and a sheet carrier concentration similar to 5 10(12) cm(-2). The variation of the conductivity with temperature, in the range 60 - 150 K, follows a In sigma proportional to T-1/4 dependence characteristic of variable range hopping. An analysis of the experimental results of conductivity as a function of temperature, in terms of possible doping effects, as well as conduction mechanisms is presented.