DEVELOPMENT OF A TWO DEGREES OF FREEDOM LENGTH MEASUREMENT SYSTEM USING A CRYSTAL AS THE SCALE REFERENCE

我们研究了利用晶体的晶格间距进行测量和精确定位的可能性。为了开展这项研究，我们建立了一台具有两个隧道单元(一个双隧道单元STM，DTU-STM)的扫描隧道显微镜(STM)，带有一个带有两个样品夹持器的XY工作台，这种结构可以同时观察一个样品和标尺参考晶体。结果，可以通过叠加晶格图像来校准样本图像的横向尺度。为了考察这一测量过程的准确性，我们比较了用两个隧道单元同时获得的晶格图像。匹配度为99.98+/-0.03%。虽然我们还没有测量到系统的绝对精度，但实验的高重复性意味着该程序可以提供良好的结果。我们已经成功地完成了原子特征的软件识别，因此可以肯定地认为，在不久的将来将实现一台能够测量到几微米的自动测量机。此外，还研究了使用STM和晶体进行XY工作台的亚纳米定位控制。利用10 pm量级的横向位置调制，以原子分辨率测量表面的梯度。通过这种技术，可以识别地形特征的局部最大值和最小值，从而实现以点阵间距为基准的XY工作台的主动定位。扫描隧道显微镜针尖与单个原子的定位也被确认了数十分钟。

We have investigated the possibility of using the lattice spacing of a crystal for metrology and accurate positioning. To carry out the research, we have built a scanning tunneling microscope (STM) with two tunneling-units (a dual tunneling-unit STM, DTU-STM), with an xy stage with two sample holders, The configuration enables simultaneous observation of a sample and the scale-reference crystal. As a result, it is possible to calibrate the lateral scales of the sample image by superposition of the crystalline lattice image. In order to access the accuracy of this measurement procedure, we have compared crystalline lattice images acquired simultaneously with the two tunneling-units. Matching of 99.98 +/- 0.03%. Although we have not measured the absolute accuracy of the system, the high repeatability of the experiment implies the procedure to give good results. We have succeeded in the software recognition of the atomic features, so it is safe to assume that an automated measurement machine, capable of measuring up to a few microns will be implemented in the near future.Study on the use of the STM and a crystal for sub-nanometer positioning control of the xy stage was also carried out. Lateral position modulation in the 10 pm order was used to measure the gradient of the surface with atomic resolution. By this technique, it becomes possible to recognize the local maximum and minimum of the topographic features, and thus implement active positioning of the xy stage using the lattice spacing as the reference. Positioning of the STM tip to a single atom was also confirmed for tens of minutes.