Atomic layer deposition of CdxZn1−xS films

Abstract

Deposition of CdxZn1−xS has been demonstrated with atomic layer deposition (ALD) using diethylzinc (DEZn), dimethylcadmium (DMCd), and hydrogen sulfide as the precursors, and DFT calculations were performed to simulate the ALD process and the properties of the deposited films. The relative ratio of the pulses is varied for DMCd and DEZn to achieve different compositions over the spectrum from pure CdS to pure ZnS. Overall, the cadmium content in the films is higher than would be expected both as a function of pulse ratio and of temperature based on the growth rates of the binary films. At 150 °C pure ZnS shows almost pure cubic nature; however, the wurtzite content increases with the presence of cadmium until the film is approximately 10% wurtzite for pure CdS. Transmission electron microscopy (TEM) with high resolution confirms the coexistence of zincblende and wurtzite within grains due to the presence of stacking faults. The roughness of the films is a function of the composition, and the band gap and index of refraction can be finely tuned with composition.