Real-time analysis of adsorption processes of Zn on the GaAs(001)-(2×4) surface

We have studied adsorption processes of Zn on the GaAs(001)-(2×4) surface using reflection high-energy electron diffraction (RHEED) and total-reflection-angle x-ray spectroscopy in real time. A rocking-curve analysis of RHEED has been used to determine the atomic coordinates of both clean and Zn-adsorbed 2×4 surfaces. The analysis for the clean 2×4 surface (ß2 phase) has shown that both As dimers in the outermost and third atomic layers are displaced upward from their bulk positions. When the 2×4 surface was exposed to a Zn beam, the Zn atoms are preferably adsorbed at Ga-vacancy sites in the missing dimer trenches of the 2×4 unit cell with site occupancies of 100% and 50% at 200 and 250 °C, respectively.