REFLECTION HIGH-ENERGY ELECTRON-DIFFRACTION AND PHOTOEMISSION-STUDY OF GASB(1OO) RECONSTRUCTIONS

The clean GaSb(100) surface exhibits a variety of reconstructions, inc luding a c(2X10), a c(2X6), and a (1X3)/c(2X6), in order of a decreasi ng surface Sb/Ga ratio. Core-level photoemission spectroscopy and refl ection high-energy electron diffraction were employed to study each of these reconstructions in detail. Our results show that the c(2X6) and (1X3)/c(2X6) surfaces have significantly different stoichiometries an d core-level line shapes, and are, in fact, different reconstructions, rather than variations of the same c(2X6) surface due to disorder. An alysis of the photoemission data taken with a wide range of incident p hoton energy suggests that the c(2X10) surface is very Sb rich, with m ore than 2 ML of Sb, while the c(2X6) has 1-2/3 ML of Sb, and the (1X3 )/c(2X6) has about 1-2/3 ML of Sb with 1/3 ML of Ga atoms intermixed o n the surface. Quantum-mechanical diffraction and interference effects are found to significantly affect the measurement of surface-to-bulk photoemission intensity ratios. Surface structure models are presented for each reconstruction which are consistent with the observed data.