Nucleation and growth mechanism of CdTe cluster grown on CdS films

The growth of CdTe films on CdS/glass was investigated. Using atomic force microscopy (AFM), we have obtained images of the coverage of CdTe deposited by radio-frequency magnetron sputtering (RF sputtering) on a CdS substrate. A nucleation kinetics model has been derived from the analysis of the particle size distribution observed by AFM. The reconstructed nucleation process was characterized by a systematic behaviour. The nucleation rate, negligible at the beginning, reaches a maximum after a certain time and then tends to zero for a longer deposition time. The nucleation process shows a temperature-dependent incubation time. The incubation time is related to the time of formation of a “critical CdTe cluster”. The size of the critical cluster is explained by the thermodynamic properties of the system and by the amount of interface misfit strain energy of CdTe lattice with respect to the substrate. The films were deposited at a substrate temperature of 250, 300, 350 and 400 °C, the incubation time calculated values are 817, 503, 283 and 68 s for each temperature, respectively, and the activation energy that the CdTe molecules have to overcome to pass from the gas phase to the solid phase have been found to be 0.332±0.003 eV.