Vibrational and electronic excitations at GaN{0001} surfaces

The vibrational properties of clean, H- and D-covered GaN{0001} surfaces as well as electronic excitations were investigated by high-resolution electr on energy-loss spectroscopy. Surface cleanliness and structure were monitor ed by Auger electron spectroscopy and low-energy electron diffraction. At h ydrogenated surfaces H-Ga and H-N stretching vibrations were found at 1900 cm(-1) (235.6 meV) and 3255 cm(-1) (403.6 meV), respectively. After deutera tion a D-N stretching as well as a D-Ga bending mode were detected at 2395 cm(-1) (297.0 meV) and 390 cm(-1) (48.4 meV). From the isotope shift of the stretching vibrations, the periodic displacement of the N atoms is calcula ted. In the electronic loss regime, a transition from band gap states was f ound to vanish after H exposure. (C) 2000 Elsevier Science B.V. All rights reserved.