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

我们已经研究了使用晶体的晶格间距进行计量和精确定位的可能性。为了进行研究，我们已经建立了一个扫描隧道显微镜（STM）与两个隧道单元（一个双隧道单元STM，DTU-STM），与一个xy级与两个样品架，配置使样品和标度参考晶体的同时观察。结果，可以通过晶格图像的叠加来校准样品图像的横向尺度。为了访问这个测量过程的准确性，我们比较了同时获得的晶格图像与两个隧道单元。匹配度为99.98 +/-0.03%。虽然我们还没有测量系统的绝对精度，但实验的高重复性意味着该程序可以获得良好的结果。我们已经成功地在软件中识别的原子功能，所以它是安全的假设，一个自动化的测量机器，能够测量到几个微米将在不久的将来实现。研究使用STM和晶体的亚纳米定位控制的xy阶段也进行了。横向位置调制在10 μ m的顺序被用来测量原子分辨率的表面的梯度。通过这种技术，可以识别局部最大值和最小值的地形特征，从而实现主动定位的xy平台使用的晶格间距作为参考。STM针尖对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.