Kinetics of CdTe(100) sublimation

One of the processes involved in the deposition of CdTe solar cells is closed-space sublimation. While a few first-principles calculations of the binding energies of Cd and Te atoms and/or Cd_xTe_y clusters have been carried out, the relevant desorption barriers and prefactors are still not known. In addition, experimental measurements of the temperature-dependent sublimation rate from the (100) CdTe surface have led to two significantly different values for the effective activation energy, depending on which experimental technique was used.  Here we present the results of accelerated molecular dynamics simulations of Cd atom, Te atom, and Te₂ dimer desorption for a variety of different configurations of the Cd-terminated and Te-terminated (100) surface which we have used to obtain key barriers and prefactors. Based on a steady-state assumption we find surprisingly good quantitative agreement between the temperature-dependent sublimation rate estimated from our simulations and experimental results.  Our results also provide quantitative support for a previous suggestion that the sublimation rate is determined by a competition between two processes: vacancy nucleation and step-flow, each of which corresponds to a different activation barrier and turns on at different temperatures.