Interface-state-controlled segregation of gold during ion-beam-induced epitaxy of amorphous silicon

Segregation coefficients and velocity enhancements for Au in amorphous Si during ion-beam-induced epitaxial crystallization were measured. At 320°C, velocity enhancements of up to 2.5 times were observed, and interface breakdown occurred at interfacial Au concentrations of 11 at. %. Although qualitatively similar to thermal solid-phase epitaxy, these velocity enhancements are substantially reduced in magnitude while the interface breakdown occurs at much higher concentrations. Between 250°C and 400°C, Au is trapped at the moving interface with segregation coefficients k, which are approximately velocity and concentration independent and vary between 0.001 and 0.012. In contrast with classical segregation, however, k increases linearly with interface position during the initial stages of growth to a temperature- dependent steady-state value. At 250°C, for example, k increases by at least a factor of 4 to 0.012 during growth. These results suggest an evolving interface structure from the initial thermal configuration to an irradiation-induced steady-state configuration with a higher trapping efficiency.