On the growth mechanism of an A-B crystal: II. effect of dissociative adsorption of B2 molecules

In a previous treatment, the BCF theory which applies to a monatomic crystal has been extended to the case of an A-B crystal growing from the vapour according to a scheme A(g) + B(g) ? AB(cr).The effect of dissociative adsorption of diatomic gas molecules according to a scheme A(g) + 1/2 B₂(g)?AB(cr) is incorporated in the present work. The results obtained are as follows. (i) The growth rate for a constant driving force Δg = kT lnP_A(P_B2)^1/2/P_A0(P_B201/2] varies with the partial pressures P_A and P_B2. (ii) In the limiting cases, P_A å P_B2 or P_A å P_B2, the major component is nearly under saturation and the growth rate is me$\text{r}$ely controlled by the minor component, which works as the so-called “growth unit”. (iii) Because of the associative desorption of B adatoms, the mean migration distance $\text{x}$_sB depends on the partial pressure P_B2. (iv) The theory is in good agreement with an experiment on the vapour growth of CdTe under controlled partial pressure of the constituent element.