HREELS investigation of hydrogenated and deuterated GaN{0001} surfaces

The vibrational properties of clean, H- and D-covered GaN{0001} surfaces we re investigated by high-resolution electron energy-loss spectroscopy Anger electron spectroscopy and low-energy electron diffraction were utilized to monitor the surface cleanliness and structure, respectively. At the clean s urface the Fuchs-Kliewer surface phonon frequency was determined to 700 cm( -1) (86.8 meV). For the adsorbate-covered surfaces current structure models predict only Ga-H vibrations for surfaces of either polarity. Despite of t his, the HREEL-spectra of the hydrogenated sample show a new loss structure at 3255 cm(-1) (403.6 meV) and a shoulder at 1900 cm(-1) (235.6 meV) which are attributed to N-H and Ga-H stretching vibrations, respectively. After deuterium exposure an isotope shift occurs. Again, a N-adsorbate vibration is clearly resolved. A Ga-D bending: mode is observed at 390 cm(-1) (48.4 m eV). indicating that vibrations of both species are present.