Growth of (110) diamond using pure dicarbon - art. no. 165414

We use a density-functional-based tight-binding method to study diamond gro wth steps by depositing dicarbon species onto a hydrogen-free diamond (110) surface. Subsequent C-2 molecules are deposited on an initially clean surf ace, in the vicinity of a growing adsorbate cluster, and finally near vacan cies just before completion of a full new monolayer. The preferred growth s tages arise from C-2n clusters in near ideal lattice positions forming zigz ag chains running along the [(1$) over bar 10] direction parallel to the su rface. The adsorption energies are consistently exothermic by 8-10 eV per C -2, depending on the size of the cluster. The deposition barriers for these processes are in the range of 0.0-0.6 eV. For deposition sites above C-2n clusters the adsorption energies are smaller by 3 eV, but diffusion to more stable positions is feasible. We also perform simulations of the diffusion of C-2 molecules On the surface in the vicinity of existing adsorbate clus ters using a constrained conjugate gradient method. We find migration barri ers in excess of 3 eV on the clean surface, and 0.6-1.0 eV on top bf graphe nelike adsorbates. The barrier heights and pathways indicate that the growt h from gaseous dicarbon proceeds either by direct adsorption onto clean sit es or after migration on top of the existing C-2n chains.