Functionalizing the GaN(0001)-(1 x 1) Surface. I. The Chemisorption of Aniline
NAVAL RESEARCH LAB WASHINGTON DC
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Chemisorption of aniline C6H5NH2 on the GaN0001-1x1 Ga-polar surface has been studied using mainly Xray-excited Auger electron, electron energy loss and ultraviolet photoemission spectroscopies XAES, ELS and UPS respectively. The XAES data show adsorption near room temperature with a total sticking probability of 0.05 and a saturation coverage of 0.28 phenyl rings per surface lattice site. The ELS data show removal of the characteristic surface-state band centered at 3.4 eV and the appearance of a pi to pi loss at 6.5 eV due to CC bonds. In contrast benzene C6H6 does not chemisorb under these conditions. The UPS data, which have been analyzed with the aid of density functional theory molecular orbital calculations, indicate that adsorption occurs with a phenyl-NH group forming a Ga-N-Ga bridge. Adsorption causes a decrease in electron affinity delta chi is approximately -0.55 eV due to a surface dipole layer, and measurement of delta chi and of changes in band bending have been used to construct a partial energy level diagram for the aniline-covered surface.
- Physical Chemistry
- Solid State Physics