Manufacture of p-type ZnO thin film by co-sputtering of Zn and Li ₂CO₃ targets simultaneously

The ZnO thin film has been the subject of much research in recent years due to its varied potential applications for optoelectronic devices. However, the p-type ZnO film conduction with low resistivity is difficult to achieve because of self-compensation effect of the opposite charge carriers in the material itself and low solubility of extrinsic doping acceptors. In this work, lithium-doped ZnO films were grown on glass substrates by RF reactive magnetron sputtering using Zn metal target with several Li₂CO₃ piece meals on it. This study examined the effect of Li content on the conduction and optical of ZnO thin films by r.f. magnetron sputtering. The structural, electrical and optical properties of the deposited films were strongly influenced by various Li content. The Li compositions of the ZnO thin films were determined by ICP-MS. Elemental depth profiles were performed by SIMS analysis. The structure characterization was used by GIAXRD measurement. Hot probes and Hall measurement were used to determine the resistivity, carrier density and mobility. The GIAXRD analysis indicated that the ZnO:Li films have (002) preferred orientation. The optical transmission spectra show a high transmittance (∼80%) in the visible region. The lowest resistivity of as-grown p-type ZnO:Li film is 4.72x10^-1 ohm-cm. A p-type conductive behavior was confirmed by the Hall effect measurement for these ZnO:Li films with a carrier concentration of 2.47x10¹⁹cm^-3 and hall mobility of 0.85 cm²/V-sec.