Comparison of Lateral Crystal Growth in Selenium Thin Films and Surface of Bulk Samples

Crystal growth in the surface of selenium bulk samples and in selenium thin films of different thicknesses has been studied under isothermal conditions using different microscopy techniques (optical, infrared, and scanning electron microscopy). The structure of the formed crystals is described with respect to previous publications focused on crystal growth in selenium thin films and bulk samples. Crystal growth rates were obtained from the linear dependence of crystal sizes on annealing time. Such behavior assumes that crystal growth is driven by liquid-crystal interface kinetics. The crystal growth rates found in the surface of bulk samples are comparable with those found in thin films and a few orders of magnitude higher than previously published growth rates of volume crystals formed in selenium undercooled melts. The crystal growth rates were scaled with the viscosities to analyze the Stokes-Einstein relation. A relatively high decoupling between the crystal growth rate and viscosity occurs in the studied samples of amorphous selenium. Therefore, the standard screw dislocation growth model is corrected for the decoupling, which provides a satisfactory description of the crystal growth rate over a wide temperature range.