Theoretical study of hydrogenated 3C-SiC(001)-(2 x 1) surface

The atomic structure and electronic states of the hydrogenated 3C-SiC(001)-(2 x 1) surface are investigated by the first-principles calculations. Two models of the hydrogenated surfaces are studied, i.e., the hydrogenated alternating up and down dimer (AUDD) surface and the missing row asymmetric dimer (MRAD) surface, respectively. It is found that the length of the dimers on monohydrided AUDD surface is significantly reduced after hydrogenation, in sharp contrast to the case of Si(001)-(2 x 1) surface on which the dimers become longer after hydrogenation. The strengthening of the dimers on monohydrided AUDD surface can explain the strong S-state observed in experiments. In the calculated partial density of states (PDOS) of the adsorbed hydrogen atoms on monohydrided AUDD surface, there is only one sharp peak at the energy of about 2.6 eV below the valence band maximum (VBM), in good agreement with the recent photoemission experiments. This binding energy is considerably lower than that of the hydrogen-induced states on Si(001) surface. The reduction of the dimer length, the strong S-state, and the low binding energy of the hydrogen-induced states on the monohydrided AUDD surface can be uniformly explained by the smaller lattice constant of SiC and the stronger Coulomb interaction between the adsorbed H atoms. In the PDOS of the hydrogen atoms on dihydrided MRAD surface, there are several large peaks with the main surface resonance peak located at about 4 eV below the VBM. The calculation shows that the position of the calculated hydrogen-induced states of monohydrided AUDD surface agrees with the photoemission experiments. (C) 2004 Elsevier B.V. All rights reserved.