Migration enhanced epitaxy

A schematic phase diagram of MBE growth is depicted in fig. 4 (Ohno 1998 Shen et al. 1999). Recently it was shown that metallic (Ga,Mn)As with x = 0.1 can be obtained by the use of a modified MBE growth technique at 7s = 150°C, migration-enhanced epitaxy (MEE), where the beam fluxes of source materials are precisely controlled (Sadowski et al. 2001a, 2001b). 

The dose required for amorphization is a function of the kinetics of simultaneous dynamic recovery processes. The recovery process is accelerated at elevated temperatures and, in many cases, is greatly increased by radiation-enhanced defect migration. These simultaneous recovery processes may be associated with defect recombination or annihilation, epitaxial recrystallization at crystalline-amorphous interfaces (Carter and Nobes 1991), or nucleation and growth recrystallization in the bulk of the amorphous state. For any crystalline solid, there is a critical temperature, above which the rate of amorphization is less than the rate of recovery, thus amorphization cannot occur. However, Tc also depends on the energy and mass of the incident beam, as well as the dose rate. 

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