Asorption Behavior Of Graphene On The Chemically Decorated Si（111） Surface And The New Two-dimension SiC₂Material’s Prediction

Graphene, a single layer of carbon atoms arranged in a honeycomb lattice, is atypical sp2-hybrid material. It is considered as a potential candidate to replace Si asthe basic material for next generation nanoelectronic device due to its excellentelectronic properties. The realization of the synthesis of graphene on Si surface is thefoundation of graphene in combination with Si technology. To preseve the electroniccharacter of graphene on the Si（111） surface is the premise for graphene-basednanodevices. In this paper, we investigate the electronic characteristics of graphene onthe C-decorated Si（111） surface which provides some theoretical fundamentalsfor the growth of graphene on the Si surface. In our present work we alsofind a new kind of SiC₂two-demisonal material, its structure and electronic propertiesare predicted. The main points of our present work are as follows:（1） First principles calculations based on the density functional theory areperformed to study electronic structures of graphene adsorbed on clean or C-decoratedSi（111） surface. Two types of surface reconstructions,22and33, areconsidered to be decorated by carbon atoms with different concentrations. Firstly, wefind that graphene adsorbed on ideal clean Si（111） surface tends to induce a21reconstruction, and the electronic characteristics of graphene are preserved. We findthat the decoration of carbon atoms on the Si（111） surface can effectively passivatethe Si dangling bonds on the surface. Such decoration effects make the carbondecorated Si（111） surfaces promising substrate for graphene which preserves theexcellent electronic structure of graphene;（2） We investigate the the modified effect of hydrogen（H）, boron（B）,nitrogen（N）, fluorine（F） adsorbed Si（111） surface on the electronic properties ofgraphene by using the fisrt-principles method based on density functional theory. Theresults indicate that the H,B,N,F adsrobates can effectively saturate the danglingbonds on the Si（111） surface. When asorbed on the H, B, N, and F decorated Si（111）surface, the graphene only weakly interact with the surface. It is belongs to physicaladsorption. The graphene displays p-type doping when adsorbed on the H, N, and Fdecorated Si（111） surface, whereas the graphene displays n-type doping whenadsorbed on B decorated Si（111） surface. This provides an effective method tomodulate of the conduction types of graphene on the Si surface; （3） We propose a novel two-dimensional nano-sheet of SiC₂（SiC₂-pentagon）consisting of tetrahedral silicon atoms and triple-linked carbon atoms in afully-pentagon network. The SiC₂-pentagon with buckled configuration is morefavorable than its planar version and the previously proposed SiC₂-silagraphene withtetracoordinate silicon atoms. Buckled SiC₂-pentagon is an indirect-band-gapsemiconductor with a gap of1.388eV and confirmed dynamically stable. Itsone-dimensional nanoribbons can be metals or semiconductors depending on the edgetypes, shapes and decorations. Finally, we propose a method to produce the buckledSiC₂pentagon through chemical exfoliation on the SiC（001）-c（2×2） SDBsurface.