The hydrogenated and bare diamond (110) surface: a combined LEED-, XPS-, and ARPES study

The atomic and electronic structures of the hydrogenated and hydrogen-free diamond (110) surface are investigated by low-energy electron diffraction ( LEED), angle-resolved photoelectron spectroscopy (ARPES), and X-ray induced core-level spectroscopy (XPS). From the C 1s core-level spectra, different states of surface termination can be distinguished. The plasma-hydrogenate d surface exhibits a surface C 1s component shifted by 0.8 eV towards a hig her binding energy, which we attribute to coadsorbed hydrocarbons. During t hermal annealing up to 900 degrees C, gradual desorption first of the hydro carbons and then of hydrogen yields a clean surface with a surface C 1s com ponent shifted by -1.1 eV and an increase in downward band bending of about 1.2 eV compared to the as-prepared surface. From the valence band spectra, we conclude that an essentially hydrogen-terminated surface is maintained at an annealing temperature of 600-800 degrees C. All states of the surface are unreconstructed. After the plasma treatment, the surface reveals monoa tomic steps running parallel to the [1(1) over bar 0] direction. From an an alysis of the extinction of LEED reflexes, we conclude that within the chai ns of surface atoms running along [1(1) over bar 0], the C-C bond length is uniformly altered in a way that keeps the chains undimerized. Finally, for the hydrogen-free surface, an occupied surface band is observed with a dis persion of 0.35 eV between <(Gamma)over bar> and (J) over bar that lies ent irely below the valence band maximum. (C) 1999 Published by Elsevier Scienc e B.V. All rights reserved.