IN-SITU MONITORING OF THE C(4X4) TO THE 2X4 SURFACE PHASE-TRANSFORMATION ON GAAS(001) BY GRAZING-INCIDENCE X-RAY-DIFFRACTION

The transition between the arsenic saturated c(4 X 4) and the As stabi lised 2 X 4 reconstructed GaAs(001) surfaces has been followed in situ on a UHV grazing incidence X-ray diffractometer stage. X-ray diffract ion lines specific of either structure have been recorded as a functio n of temperature. The intensity and lineshape evolution has enabled to propose a model for the transformation involving a homogeneous disord ering of the c(4 X 4) surface through random As desorption followed by nucleation and growth of 2 X 4 domains. Under UHV conditions, the irr eversible transition is observed over a temperature interval ranging f rom 330 degrees C to 380 degrees C.