An investigation of the dip-Ion Layer Gas Reaction process to produce ZnO films with increased deposition rates

Intrinsic ZnO thin film layers have previously been deposited using the dip-ILGAR ‘Ion Layer Gas Reaction’ method. This deposition method and material has been effectively employed to deposit the buffer layers in chalcopyrite solar cells [M. Bär, H.-J. Muffler, Ch.-H. Fischer, S. Zweigart, F. Karg, M.C. Lux-Steiner Prog. Photovolt: Res. Appl. 10 (2002) 173]. The original parameters for the ZnO dip ILGAR deposition process were optimised for film quality. These parameters, however, were not suitable for an up-scaled technology transfer to tape deposition as the dip speed and growth rate meant impractically long deposition times. The results presented here are from an investigation, using the laboratory scale ILGAR apparatus with 2.5×5 cm2 substrates, into parameters e.g. solvent, salt and apparatus parameters, which could allow an increased deposition rate and dip speed yet retains film quality. Simple dip mechanics and the Landau–Levich equation, which describes film thickness as a function of dip withdrawal speed, gravitational acceleration and the properties of the solution, are considered. The recently optimised deposition parameters given here will allow a dip speed of more than 7 m/min and deposition rate of 7.5 nm/cycle.