Graduate School of Engineering, Osaka University, 2-1 Yamada-Oka, Suita, Osaka 565-0871, Japan.
ACS Nano. 2013 Aug 27;7(8):7370-6. doi: 10.1021/nn403097p. Epub 2013 Aug 1.
The effect of tip chemical reactivity on the lateral manipulation of intrinsic Si adatoms toward a vacancy site on a Si(111)-(7 × 7) surface has been investigated by noncontact atomic force microscopy at room temperature. Here we measure the atom-hopping probabilities associated with different manipulation processes as a function of the tip-surface distance by means of constant height scans with chemically different types of tips. The interactions between different tips and Si atoms are evaluated by force spectroscopic measurements. Our results demonstrate that the ability to manipulate Si adatoms depends extremely on the chemical nature of the tip apex and is correlated with the maximal attractive force measured over Si adatoms. We rationalize the observed dependence of the atom manipulation process on tip-apex chemical reactivity by means of density functional theory calculations. The results of these calculations suggest that the ability to reduce the energy barrier associated with the Si adatom movement depends profoundly on tip chemical reactivity and that the level of energy barrier reduction is higher with tips that exhibit high chemical reactivity with Si adatoms. The results of this study provide a better way to control the efficiency of the atomic manipulation process for chemisorption systems.
室温下，通过非接触原子力显微镜研究了尖端化学活性对固有 Si 原子在 Si(111)-(7×7)表面空位处横向操纵的影响。在这里，我们通过使用具有不同化学性质的尖端进行恒高扫描，测量了与不同操纵过程相关的原子跳跃概率作为尖端-表面距离的函数。通过力谱测量评估了不同尖端和 Si 原子之间的相互作用。我们的结果表明，操纵 Si 原子的能力极大地取决于尖端顶点的化学性质，并与在 Si 原子上测量的最大吸引力相关。我们通过密度泛函理论计算合理化了观察到的原子操纵过程对尖端顶点化学活性的依赖性。这些计算的结果表明，降低与 Si 原子迁移相关的能量势垒的能力极大地取决于尖端的化学活性，并且与 Si 原子具有高化学活性的尖端相比，降低能量势垒的水平更高。这项研究的结果为控制化学吸附体系中原子操纵过程的效率提供了更好的方法。
