Compositional effects accompanying near equilibrium vapour growth of solid solution crystals of the types IV‐VI and II‐VI

Abstract

Near equilibrium evaporation-condensation in a sealed ampoule leads to almost full compositional reproduction of a solid solution if it consists of components having comparable vapour pressures; this can be qualitatively interpreted by domination of entropy increase. Nevertheless, even vestigial separation requires closer characteristics, since it may prove crucial -particularly for properties of semiconducting solid solutions. Maximum component separation allowed by a small temperature difference is described here in terms of thermodynamics and kinetics of solid-vapour and vapour-solid phase transitions. Theoretical models of the determining effects having different character are shortly described, and their applicability areas are determined. Experimental data collected for crystal growth of numerous semiconducting solid solutions of the II-VI and IV-VI type support the conclusion drawn from the models that the near equilibrium crystal growth from the vapour in a closed system ensures the highest degree of compositional uniformity.

Monocrystalline Cd0.2Zn0.8Te solid solution obtained by self‐selecting vapour growth

“…The difference in x of 0.02 between the produced crystal and the part of remainders is larger than usually observed for the SSVG method. We attribute it to considerably smaller volatility of ZnTe than of CdTe and also (stronger than usual) deviation of the ampoule interior from isothermal character -it was shown that the limit of separation degree in a closed, near equilibrium system is a growing function of deviation from isothermal conditions [32].…”

“…The method of self-selecting vapour growth SSVG, which is based on formation of specific temperature field [31], provides most favourable conditions for undisturbed vapour growth of monocrystals, since it ensures best reduction of influence of any foreign material on the growing crystal. Simultaneously, a near isothermal, closed system ensures in general the lowest level of compositional gradients [32], when solid solution crystals are grown. Therefore, compositional differences remain near to the detection limit of most sensitive analytical techniques.…”

Proposição de uma nova rota simplificada para a síntese de pontos quânticos coloidais de CdTe: caracterização e estudo da cinética de crescimento

“…e σ , na qual σ, o parâmetro exponencial da equação de Gibbs-Thomson, é deőnido por σ ≡ 2γVm rcRT , onde γ é o termo de energia de superfície para o CdTe, R é a constante universal dos gases, r C é o raio crítico, a partir do qual os PQs se formam, T é a temperatura do meio reacional e V m é o volume molar, que para o CdTe vale 38,711 cm 3 mol [71]. Para seguirmos adiante com o cálculo da concentração de equilíbrio, precisamos determinar primeiramente o raio crítico.…”