Transport properties of non magnetic and magnetic ZnO thin films under Field Effect

摘要

The integration of ZnO based high mobility transparent semiconductors with perovskites that exhibit a wide spectrum of physical properties (superconductivity, ferroelectricity, ferromagnetism, etc.) may lead to a wide variety of new electronic/optoelectronic devices. Here we present results about the deposition of high crystalline quality Al or Co doped ZnO films grown by pulsed laser deposition on 110 face of strontium titanate single crystals. Field Effect (FE) experiment, allowing to change the carrier concentration of the film by more then 4 orders of magnitude (from ≈ 10~(15) to ≈ 10~(20) e-/cm~3, estimated by Hall effect measurements under FE), were employed to investigate transport mechanisms in depth. In particular we observed a crossover of low temperature magnetoresistance from a negative behaviour in the accumulation state to a positive one in the depletion state. The measurement of the activation energy as a function of the Gate potential allowed to get information on the density of states.