A Study on the Step Growth Kinetics of KDP Crystal by Michelson Laser Interferometer Experiment

The dislocation hillock slope and the normal growth rate determined by this dislocation source were simultaneously measured by using the Michelson laser interferometer technology. The crystal growth kinetic parameters, including the step growth kinetic coefficient and step free energy are measured or calculated and the mass diffusion characters on the step plane and the activity of different dislocation sources are discussed. It has been shown that the step kinetic coefficients have significant differences between high and low-activity dislocation sources. For example, the step kinetic coefficients are calculated to be 10.3×10-2 and 5.21×10-2 cm/s for high-activity and low-activity steps, respectively. The most important conclusion is that the surface diffusion does not play a noticeable role in the crystal growth of KDP. It has been believed that the variations of the shape and size of dislocation sources, along with the change of Burgers vectors, are the main reasons for the poor repeatability of kinetic experimental data of KDP crystals.