Temperature-dependent changes on the sulfur-passivated GaAs (111)<i>A</i>, (100), and (111)<i>B</i>surfaces

Abstract

The chemical bonding changes as a function of temperature in sulfur-passivated GaAs (111)A, (100), and (111)B surfaces were monitored in situ by synchrotron-radiation photoelectron spectroscopy. At relatively low temperatures (T\ensuremath{\simeq}200 \ifmmode^\circ\else\textdegree\fi{}C), As-S bonds are converted to Ga-S bonds. At higher temperatures, a well-ordered monolayer is observed and a predesorption state is observed for both the (111)A and (111)B surfaces at about 50 \ifmmode^\circ\else\textdegree\fi{}C below the S desorption temperature for the respective surfaces. It is also found that the S desorption temperature is well correlated with the coordination number of the sulfur atom on the GaAs surface.