Ultrahigh-vacuum four-circle diffractometer for grazing incidence x-ray diffraction on i n s i t u MBE grown III-V semiconductor surfaces

Abstract

An ultrahigh-vacuum compatible four-circle diffractometer coupled to a molecular-beam epitaxy growth chamber has been designed to collect grazing-incidence x-ray diffraction (GIXD) spectra on in situ grown III-V semiconductor surfaces and interfaces. The unit is on line at the D25 bending magnet beam port of the LURE-DCI hard x-ray synchrotron-radiation facility (Orsay, France). Epilayer growth, surface processing, and diffraction data collection are performed without interruption of the ultrahigh-vacuum environment (in the low 10−10-mbar range) around the sample. The setup has been first applied to the determination of the atomic structures of GaAs(001) reconstructed surfaces. Results concerning the As-saturated c(4×4) phase are presented together with preliminary information on the As-stabilized 2×4 reconstruction.