School of Physics, Shandong University, Jinan 250100, P.R. China.
Nano-organic Photoelectronic Laboratory, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
J Chem Theory Comput. 2011 Mar 8;7(3):707-12. doi: 10.1021/ct1004998. Epub 2011 Jan 10.
We investigate the electron transport between a scanning tunneling microscope tip and Si(100)-2 × 1 surfaces with four distinct configurations by performing calculations using density functional theory and the nonequilibrium Green's function method. Interestingly, we find that the conducting mechanism is altered when the tip-surface distance varies from large to small. At a distance larger than the critical value of 4.06 Å, the conductance is increased with a reduction in distance owing to the π state arising from the silicon dimers immediately under the tip; this in turn plays a key role in facilitating a large transmission probability. In contrast, when the tip is closer to the substrate, the conductance is substantially decreased because the π state is suppressed by the interaction with the tip, and its contribution in the tunneling channels is considerably reduced.
我们通过使用密度泛函理论和非平衡格林函数方法对具有四种不同构型的扫描隧道显微镜尖端和 Si(100)-2×1 表面之间的电子输运进行了计算研究。有趣的是，我们发现当针尖-表面距离从大到小变化时，导电机制会发生改变。在距离大于 4.06Å 的临界值时，由于针尖下的硅二聚体产生的π态，电导随着距离的减小而增加；这反过来又在促进大传输概率方面起着关键作用。相比之下，当针尖更接近衬底时，电导会显著降低，因为与针尖的相互作用抑制了π态，其在隧道中的贡献大大减少。
