Ab initio Study on Carbon-Induced Modification of Si(001)

 

Hanchul Kim

 

Korea Research Institute of Standards and Science, Yuseong P.O.Box 102, Daejeon 305-600, Korea

 

Using ab initio pseudopotential calculations, we have studied the structural modification of Si(001) due to carbon incorporation. First, as for the isolated carbon incorporation, we found that the most stable configuration is the so-called DV41 defect, in which a C atom substitutes a fourth-layer Si atom under a surface Si dimer vacancy (DV). Increasing the number of incorporated carbon atoms, they start to interact. In consequence, the surface transforms into the 2 × n (n ~ 10) superstructure featuring one-dimensional DV lines on the surface. Further C-incorporation leads to the formation of the c(4×4) phase, that has been reported for several decades without microscopic understanding. Based on the experimentally measured carbon content using scanning tunneling microscopy(STM), we have determined the energetically stable atomic structures of carbon-incorporated Si(001)-c(4×4) phases. The theoretical STM images are in good accordance with the experimental data.