Optimizing the discharge voltage in magnetron sputter deposition of high quality Al-doped ZnO thin films

Abstract

Articles you may be interested inCarrier mobility of highly transparent conductive Al-doped ZnO polycrystalline films deposited by radio-frequency, direct-current, and radio-frequency-superimposed direct-current magnetron sputtering: Grain boundary effect and scattering in the grain bulk J. Appl. Phys. 117, 045304 (2015); 10.1063/1.4906353Correlations between 1/f noise and thermal treatment of Al-doped ZnO thin films deposited by direct current sputtering Transparent conducting Si-codoped Al-doped ZnO thin films prepared by magnetron sputtering using Al-doped ZnO powder targets containing SiC Transparent conducting Al-doped ZnO thin films prepared by magnetron sputtering with dc and rf powers applied in combination Investigation on the electrical properties and inhomogeneous distribution of ZnO:Al thin films prepared by dc magnetron sputtering at low deposition temperatureThe role of negative ions in the sputter deposition of oxides can be termed negative in the sense that they typically cause radiation-induced structural damage during film growth. For magnetron sputtered Al-doped ZnO (AZO) films, efforts have been made to alleviate the radiation damage by decreasing the discharge voltage jV d j, with $100 V being the lower limit explored. Here, the authors report initial results of depositing highly conductive and transparent AZO films by reducing jV d j down to 40 V. The deposition was performed by sputtering an AZO target using dense magnetron discharges, in which an 81 MHz radio frequency power was superimposed onto a DC power applied to the cathode. The authors found an optimal jV d j window within which high quality AZO films, with a <4 Â 10 À4 X cm resistivity, >30 cm 2 /(V s) Hall mobility, and >88% visible transmittance, were obtained at relatively high deposition rates (>30 nm/min). Based on the corresponding structural features, i.e., a full mass density coupled with a slight c-axis contraction along the out-of-plane direction, energetic negative ions were identified to have dominated in the structural evolution. The jV d j window was then interpreted in terms of two competitive kinetic processes simultaneously caused by the energetic negative ions: void reduction via ballistic relocation of atoms as well as residual radiation-induced damage. The findings thus reveal a positive role (i.e., concomitant densification) played by the negative ions in growing high quality fully dense AZO films, which has been overshadowed by the excessive radiation damage induced by ions with relatively higher energies.

Effective Oxygen-Defect Passivation in ZnO Thin Films Prepared by Atomic Layer Deposition Using Hydrogen Peroxide

“…Recently, n-type ZnO with high carrier concentration, high Hall mobility, and low resistivity could be prepared using various doping elements (doping with Cl, Ti, Al, Ga, and N). [12][13][14][15][16] However, the preparation of p-type ZnO with high carrier concentration and conductivity remains an unsolved problem, which prevents the commercial application of ZnO-based LEDs. 4,17) The presence of oxygen vacancies (V o ) in ZnO is one of the main barriers to preparing high-quality p-type ZnO.…”

The measurement and impact of negative oxygen ions during reactive sputter deposition

“…[257,258]. To lower the discharge voltage to even lower values, a high frequency RF (81 MHz) was superimposed to the DC power [259]. Experiments in the latter study were performed at constant DC power.…”