中文摘要：

锯齿型和扶手椅型六角形石墨烯分别跨接在两Au电极上,构成分子纳器件,同时考虑对六角形石墨烯分别进行B,N和BN局部规则掺杂.利用第一性原理方法,系统地研究了这些器件的电子输运特性.计算结果表明：B及BN掺杂到扶手椅型六角形石墨烯,对其电流有较好的调控效应,同时发现本征及掺杂后的锯齿型六角形石墨烯均表现为半导体性质,且N及BN掺杂时,表现出明显的负微分电阻现象,特别是N掺杂的情况,能呈现显著的负微分电阻效应,这也许对于发展分子开关有重要应用.通过其透射特性及掺杂诱发的六角形石墨烯电子结构的变化,对这些结果的内在原因进行了说明.

英文摘要：

Zigzag- and armchair-edged hexagonal graphenes are sandwiched between two Au electroaes to consutruct nanodevices, and the effects of the orderly and locally doped with B, N, and BN for such graphene nanoflakes are considered, respectively. Based on the first-principles method, the electronic transport properties of these devices are investigated systematically. Our calculated results show that the using of B and BN to dope armchair-edged hexagonal graphenes can modulate the electronic transport properties significantly. Intrinsic and doped zigzag-hexagonal graphenes presents a semiconductoring behavior, and when it is doped with N and BN, there appears a negative differential resistance （NDR） phenomenon, especially for N-doping, and a very obvious NDR can be observed in zigzag-edged hexagonal grapheme： this might be important for developing molecular switches. The underlying causes for these findings are clearly elucidated by the transmission features and the doping-induced changes in electronic properties of a hexagonal graphene.