Research On The Microscopic Morphology Of Surface And Growth Kinetics Of ZTS Crystal With Urea Doped

Zinc tris(thiourea) sulphate(ZTS), as a metalorganic complex of the thiourea, is a new nonlinear crystal and becoming a hot crystal material in the nonlinear optical crystal materials field, which not only has advantages of high stability, high mechanical strength and the property of high energy storage just like the inorganic crystals, but also has advantages like the organic crystal such as high nonlinear coefficient, good optical homogeneity, high laser damage threshold, high frequency doubling effect, low angle sensitivity and so on. Nowadays, the research of ZTS crystal at home and abroad is mainly focus on the effcts of different types of additives on the quality of growth, optical performance, electrical performance of ZTS crystal, while the research about the effects of additives on the microscopic morphology of surface, microscopic growth mechanism and growth rates of ZTS crystal is less. Appropriate amount of additives is helpful to improve the of growth quality and growth rate of ZTS crystal, hence, it is needed to make a research on effects of additives on the surface morphology of ZTS in order to investigate the quality of of ZTS crystal and it is needed to study the effects of additives on the growth rate and growth kinetics of ZTS crystal.In this paper, urea is selected as the additive. By the atomic force microscopy, the high precision optical microscope and other equipment, the morphology, the growth kinetics of displacement of the(100) face of ZTS crystal doped and the normal growth kinetics of ZTS crystal are studied, the main research contents and conclusions are as follows:① The solubility of ZTS crystals with different concentrations of urea doped was measured by hanging crystal method, and results show that the solubility and the solubility coefficients of ZTS crystal are both small at a low temperature, and the effect of urea on the solubility is very little; At a higher temperature, a moderate of urea doped in ZTS crystal can make an improvement of solubility, and the promoting effect is more obvious when the the temperature is higher.② The(100) face of ZTS crystal is scanned by the ex situ AFM technique. As a general rule, the morphologies of steps on(100) face of ZTS crystal with different supersaturation and doped with 2.5mol% urea are studied, and the results show both the elementary steps and macrosteps are existed. In this experimental conditions, the elementary steps are in priority on(100) face of ZTS crystal with a low supersaturation of 0.03, whose height is 0.553 nm, macrosteps are in priority on the(100) face of ZTS crystal with a high supersaturation of 0.09. The feature of step-bunching on(100) face of ZTS crystal is more serious compared with that in a pure solution. The results can make a good accord with the model of impurity motivating the asymmetrical step kinetic coefficients.③ The average displacement velocities of steps on(100) face of ZTS crystal in different conditions are measured in situ by the optical microscope, and the effect of different conditions on the displacement velocities is analyzed. The results show that with the increase of concentration of urea, the average velocities increase firstly and then decrease, reaching a maximum when the cocentration of urea is about 5mol%. The relation between the average displacement velocities of steps and the supersaturation are linear. Under the conditions of doped with low urea concentrations of 2.5mol% and 5mol%, the kinetic coefficients of steps increases, and the activation energy of steps is decreased, compared with the condition of undoped and doped with high urea concentrations of 7.5mol% and 10mol%. At the beginning stage of growth of ZTS crystal, the average displacement velocities of steps change obviously with the increase of time, and the average displacement velocities of steps stabilizes gradually.④ The normal growth rates of ZTS crystals under different conditions are measured, and the effects of different concentrations of urea on the normal growth rates are studied. The results show that the normal growth rates of(100) and(001) surfaces increase at first, then it leads to a decrease basically, however, the corresponding concentrations of urea to the maximums of normal growth rates are different. The normal growth rate of(100) face increases with the increase of concentrations of urea doped, while the trend of that slows down with high urea concentrations of 7.5mol%-10mol%. According of the factor of α, at the temperature of 298 K, it can be judged that the growth dynamics mechanisim of(100) face follows the growth model of dislocation basically, and the growth dynamics mechanisim of(010) and(001) faces mainly follow the continuous model. Finally, when the supersaturation is a constant, the higher the temperature is, the bigger the normal growth rate of(100) face behaves. The reason for that is the diffusivity of the growth units is enlarged when the temperature is higher, so the growth of crystal is promoted.