THRESHOLD BEHAVIOR IN SYNCHROTRON-RADIATION-STIMULATED RECRYSTALLIZATION DURING SI HOMOEPITAXY ON SI(100)

A brilliant synchrotron-radiation beam with a large irradiation area h as made it possible to use spectroscopic phase-modulated ellipsometry to monitor vacuum-ultraviolet-excited Si homoepitaxy. We find the crys tallinity of Si films grown at 250 degrees C from Si2H6 depends strong ly on the photon intensity. When the photon intensity is higher than a critical value, electronically excited crystallization yields epitaxi al Si. At lower intensities, however, the initial epitaxy is terminate d halfway by island-shaped regions of polycrystalline Si, which are ev entually covered by a uniform nanocrystalline Si overlayer. (C) 1997 A merican Institute of Physics.