AVS 45th International Symposium
    Surface Science Division Thursday Sessions
       Session SS-ThP

Paper SS-ThP3
Adsorption Site of Mg on GaN(0001) from Photoelectron Holography Imaging

Thursday, November 5, 1998, 5:30 pm, Room Hall A

Session: Surface Science Division Poster Session
Presenter: G.J. Lapeyre, Montana State University
Authors: S.H. Xu, Montana State University
H. Cruguel, Montana State University
Y. Yang, Montana State University
J.F. Scheitzina, North Carolina State University
G.J. Lapeyre, Montana State University
Correspondent: Click to Email
The adsorption sites of Mg on GaN(0001) with and without predosed atomic hydrogen have been determined by the small-cone photoelectron holographic imaging(PHI) technique.@footnote 1@ The experiments were performed at the Iowa/Montana State University beamline at Synchrotron Radiation Center(SRC) in Madison. The diffraction data is directly inverted without the need for models to observe the local site of the Mg emitter. The GaN samples were grown with the MOCVD method. In the analysis chamber the samples were cleaned by several heatings at about 850 °C, and the sample showed a good 1x1 LEED net. After dosing with atomic hydrogen followed by deposition of 0.5 ML Mg, the 1x1 LEED net is still observed but with a higher background. A set of 82 emission spectra by photon energy scans at the constant initial energy(CIS) of the Mg 2p level were measured. The angles for the set of CIS span a grid over one-sixth of the emission hemisphere(the surface irreducible symmetry element). The PHI images show that the adsorption sites in each case is different. With H interlayer, Mg adsorbs in a three fold site with an atom directly below the Mg emitter, usually called the T4 site. The adsorption height is about 1.4 Å above the Ga adlayer. Without the H interlayer, Mg likes to replace the Ga atoms in adlayer. The observations suggested that the H interlayer plays a key role in preventing Mg from diffusion into GaN bulk by not interchanging with the Ga atoms. This work is supported by ONR/DEPSCOR grant, SRC supported by NSF. @FootnoteText@ @footnote 1@Huasheng Wu and G. J. Lapeyre, Phys. Rev. B 51, 14549(1995)