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Construction of an experimental apparatus for atom transfer between nano-regions

纳米区域间原子转移实验装置的构建

基本信息

批准号：
05555007
负责人：
TOMITORI Masahiko
金额：
$ 5.95万
依托单位：
Japan Advanced Institute of Science and Technology, Hokuriku (1994-1995)Tokyo Institute of Technology (1993)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research (B)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1995
项目状态：
已结题

项目摘要

Recently, atom transfer in STM has attracted much interest. However, the mechanism of atom transfer in STM has not been revealed, because the experimental conditions are not always constant ; the induced high field and passing current in the proximity region between the tip and the sample are affected by the atomic structure of the tip apex. Then we have constructed a new UHV-STM/FEM with a tolerance of applying a high voltage of 10kV and increasing the tip temperature to 1500ﾟC in the STM head. The design makes possible the cleaning and build-up of the STM tip utilizing thermal field evaporation. The tip can be positioned on the surface using a 3-dimensional mechanical stage, which driven by inertia-piezomotor screws with a 30nm step. The STM and FEM operation modes can be easily switched ; the tip can be aligned to a tapered small hole of the STM sample holder, adjacent to the sample, and then the pattern of field emitted electrons from the tip can be projected on the screen behind the sample. Thus the tip apex can be evaluated before and after the experiments of atom transfer.We have studied Si (111)7x7 by STM/STS using a [111]-oriented W tip, which was built-up by heating it while applying a positive high voltage. STS measurements sweeping from-3 to 3 V resulted in unstable tunneling spectra. Immediately after the STS measurements, FEM images showed that the apex changed drastically to be darker at the center. This result indicates that the Si atoms were transferred to the tip apex by the sweeping voltages and the adsorption of Si on the tip apex increased the workfunction of the apex. This is the evidence of Si atom transfer in the STS measurements.

最近，STM 中的原子转移引起了人们的广泛兴趣。然而，STM中原子转移的机制尚未被揭示，因为实验条件并不总是恒定的；尖端和样品之间的邻近区域中的感应高场和通过电流受到尖端顶点的原子结构的影响。然后，我们构建了一个新的 UHV-STM/FEM，其耐受施加 10kV 的高压并将 STM 头中的尖端温度提高到 1500°C。该设计使得利用热场蒸发来清洁和构建 STM 尖端成为可能。可以使用 3 维机械平台将尖端定位在表面上，该平台由步进 30 nm 的惯性压电电机螺钉驱动。 STM和FEM操作模式可轻松切换；尖端可以与 STM 样品支架上靠近样品的锥形小孔对齐，然后尖端场发射电子的图案可以投影到样品后面的屏幕上。因此，可以在原子转移实验之前和之后评估尖端顶点。我们使用[111]取向的W尖端，通过STM/STS研究了Si(111)7x7，该尖端是通过在施加正高电压的同时加热它而构建的。 STS 测量范围从 3 V 扫描到 3 V 导致隧道光谱不稳定。 STS 测量后，FEM 图像立即显示顶点发生了巨大变化，中心颜色变暗。该结果表明，Si原子通过扫描电压转移到尖端顶点，并且Si在尖端顶点上的吸附增加了尖端的功函数。这是 STS 测量中 Si 原子转移的证据。