We report scanning tunneling microscopy (STM) studies of individual adatoms deposited on an InSb(110) surface. The adatoms can be reproducibly dropped off from the STM tip by voltage pulses, and impact tunneling into the surface by up to ∼100. The spatial extent and magnitude of the tunneling effect are widely tunable by imaging conditions such as bias voltage, set current and photoillumination. We attribute the effect to occupation of a (+/0) charge transition level, and switching of the associated adatom-induced band bending. The effect in STM topographic images is well reproduced by transport modeling of filling and emptying rates as a function of the tip position. STM atomic contrast and tunneling spectra are in good agreement with density functional theory calculations for In adatoms. The adatom ionization effect can extend to distances greater than 50nm away, which we attribute to the low concentration and low binding energy of the residual donors in the undoped InSb crystal. These studies demonstrate how individual atoms can be used to sensitively control current flow in nanoscale devices.

我们报告了沉积在 InSb(110) 表面上的单个吸附原子的扫描隧道显微镜 (STM) 研究。吸附原子可以通过电压脉冲从 STM 尖端可重复地脱落，并冲击隧道到表面最多 100 倍。隧道效应的空间范围和幅度可通过偏压、设定电流和光照明等成像条件进行广泛调节。我们将这种影响归因于 (+/0) 电荷跃迁能级的占据，以及相关吸附原子引起的带弯曲的切换。STM 地形图像中的效果通过填充和排空速率作为尖端位置的函数的传输建模得到了很好的再现。STM 原子​​对比度和隧穿光谱与 In 吸附原子的密度泛函理论计算非常一致。吸附原子电离效应可以扩展到大于 50nm 的距离，我们将其归因于未掺杂 InSb 晶体中残余供体的低浓度和低结合能。这些研究展示了如何使用单个原子灵敏地控制纳米级器件中的电流。