A study of deuterium interaction with diamond (110) single crystal surfaceby TPD, EELS and LEED

The present paper describes, for the first time, the desorption of deuteriu m from a degraded and well-defined microwave (MW) treated Di(110) surface. The interaction of deuterium with the Di(110) surface was studied by therma l programmed desorption (TPD), low energy electron diffraction (LEED), and low energy electron energy loss spectroscopy (EELS). It was found that hydr ogen MW plasma treatment yielded(lll) faceting on the well-defined Di(110): H surface. Heating the hydrogenated surface at 1100 degrees C in vacuum res ulted in hydrogen desorption. Activated low-coverage deuterium adsorption o n the Di(110) surface was performed in situ. From the well-defined surface, deuterium desorbed, yielding a single desorption peak, gamma(1), at simila r to 960 degrees C. Due to numerous deuterium adsorption/desorption cycles, the well-defined Di(110) surface was gradually degraded. From the degraded Di(110) surface a broad desorption peak, gamma(2), centered at similar to 660 degrees C, in addition to the gamma(1) peak, was detected in the TPD sp ectrum. It is suggested that the gamma(1) peak is associated with C-D bond breaking on the diamond structure. By contrast, it is suggested that the ga mma(2) peak is connected with desorption from different sites on non-diamon d carbon. Desorption from the gamma(1) sites was found to obey first-order kinetics. The activation energy and pre-exponential factor of deuterium des orption from gamma(1) sites were determined to be 75.5 kcal/mol and 3 x 10( 12) s(-1), respectively. A possible mechanism describing the first-order de sorption kinetics is discussed. This discussion includes a comparison with other reports and with our own results on deuterium desorption from the Di( 111) and Di(100) surfaces. (C) 1999 Elsevier Science S.A. All rights reserv ed.