Abstract
It has been a mystery how metal atoms adsorbed on perfect graphene impact the conductivity. We deposited Al, Cu, or Ag atoms onto graphene sheet on SiO2 substrate at room temperature or 573 K by pulsed laser ablation and measured the zero-gate resistance in-situ, showing that the resistance increased suddenly just after each of the deposition pulse and then decayed slowly to an elevated plateau, forming a sequential jagged peaks. Based on the fact that most areas of the graphene sheet are of perfect lattice structure, our calculations via first principles suggest that the resistance peaks result directly from the contribution of metal atoms landed on the perfect regions, and decaying of the peaks corresponds to the clustering process of the metal atoms.
Highlights
In the past few years, studies of metal atoms decorated graphene[1] have attracted considerable attentions
Depositing Ag atoms by DC plasma on graphene sheet adhered on the surface of SiO2 with a thickness of 300 nm over doped Si, Li et al observed that the metal atoms formed clusters and the conductivity decreased by about one order of magnitude at room temperature (RT), and the samples behaved even as insulators when the temperature was decreased down to 1.8 K.8
Number density of the metal atoms deposited by single pulse should be small enough so that most of the atoms initially landed on the graphene sheet are isolated and significantly distant from each other, otherwise, the diffusing and clustering process would not be clearly observed via the resistance changing
Summary
In the past few years, studies of metal atoms decorated graphene[1] have attracted considerable attentions. First-principles calculations[2,3,4] showed that Al, Cu or Ag atoms can be adsorbed on the surface by weak bonding resulting in n-type doping, indicating an increased conductivity. On realistic graphene with unavoidable defects, first-principle calculations of the conductivity is difficult for large defect and the reported experimental works are limited. Depositing Ag atoms by DC plasma on graphene sheet adhered on the surface of SiO2 with a thickness of 300 nm over doped Si, Li et al observed that the metal atoms formed clusters and the conductivity decreased by about one order of magnitude at room temperature (RT), and the samples behaved even as insulators when the temperature was decreased down to 1.8 K.8. In order to further understand the phenomena theoretically, we performed first principle calculations to give some explanations
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