First-Principles Study Of Si/Ge Adsorption On Doping Graphene

Graphene, which was first created in 2004, have attracted large attention as a potential application in the field of microeletronics and fundamental physics because of its unique mechanical and electrical properties. In this paper, we carry out a first principles study of Si/Ge adsorption on vacancy and doping graphene. We focus our attention on the electronic structures of the systems as well as their magnetic properties induced by adsorption.We optimized the bulk diamond structure C, employing US-PP (Ustralsoft-pseudopotential). We calculated the lattice constant of graphene is 2.468 ?, which is slightly larger than the experimental value of 2.46 ?. In this work, the lattice constant of the graphene is assumed to take the theoretical values. The different adsorption structure of Si/Ge on pefect graphene and the relation of formation energy versus coverage are studied. In low coverage, when the coverage increases from 1/32 ML to 1/18 ML, the change of the corresponding formation energy is small. In high coverage, when the coverage increases from 1/18 ML to 1/2 ML, the formation energy increase as the increase of the coverage. This is because of the decrease in the distance between Si/Ge atoms which duo to the coverage increasing gives rise to the interaction increasing between Si/Ge atoms.First-principle calculations are carried out to study the effects of monovacancy and Boron doping on Si adsorption on graphene. It is found that B doping graphene system is relatively stable while monovacancy system is not. B doping induces the Si stable adsorption position from bridge site to top site and increases the conductivity of graphene system. It is found that Si single atom, sitting above the bridge site of defect-free graphene, is the most stable configuration. The spin properties of C atom have changed after Si adsorption. In our calculations, monovacancy and substituting B atom enhance the Si adsorption on graphene and the effect of monovacancy deeper than the dopant B does. No magnetic moment was observed in Si adsorbed on these two systems.We investigated the effects of monovacancy,Boron and nitrogen doping on Ge adsorption on graphene. It is found that the bridge site is the most favorable site of Ge adsorption for both the perfect and boron- and nitrogen-doped graphene. Vacancy defect enhance the Ge adsorption on graphene and the effect of vacancy deeper than the dopant does. A vacancy defect will induce magnetism in graphene, but Ge-adsorption makes the system non-magnetic. Substitutional boron-doping makes graphene p-type while nitrogen impurity electron-dopes graphene. However, no magnetism is induced by such substitutional dopants. While boron doping greatly enhances Ge adsorption, N-doping seems to have little effect on Ge adsorption. In both cases, however, net magnetism is brought in upon Ge adsorption, mainly because of the contributions from p electrons in Ge.We studied the effects of Si,Al and P doping on Ge adsorption on grapheme (describe by SG,AG and PG, respectively). It is found that the site of C atom changed after Si,Al and P doping graphene. Si,P doping graphene system is relatively stable while Al doping graphene system is not. The most favorable site is different when Ge adsorption on different doped graphene system. The most favorable site of Ge adsorbed on AG system is Ge adsorbed on the top of the Al atom, while on SG and PG system Ge adsorbed on the top of the C atom. In our calculations, Al,Si and P atom enhance the Ge adsorption on graphene and the effect of Al doping deeper than the other two dopant do. No magnetic moment was observed in Ge adsorbed on AG and SG systems while net magnetism is brought in Ge adsorbed on PG system.In summary, through this work, it can be enhance the understanding of the performance of graphene and the electronic structure of the surface and semiconductor-supported graphene. Further it can reveal the physical mechanism of graphene /semiconductor interaction, and reveal the effect of various defects on the electronic structure. The study of the interaction between carbon-base materials and Si / Ge which is micro base material in IVA has important significance in the production of electronic sensors.The result of this work will have some guidance and reference value on development and application of electronic devices.