利用优化差分电路制作扫描隧道显微镜针尖

扫描隧道显微镜是一种分辨率极高的表面研究仪器，针尖对其工作过程及图像质量有决定性的影响。本文针对目前针尖腐蚀成功率较低和不稳定的缺点，提出了一种新的电路。该设计改变了反应电流的测量机制，使实际反应电压在实验过程中保持稳定，同时为了得到更加尖锐的针尖，利用差分电路监控反应过程的电流变化，能够在反应结束的瞬间立刻切断电路，避免了过度反应使针尖变钝。最后，通过观察反应电压，阴极圆环位置，差分电路灵敏度以及电解液浓度对针尖质量的影响，给出了合适的反应参数，并且比较了差分电路和传统电流阈值监控法的优缺点。结果表明新电路在稳定性上有所提高，与电流阈值监控法相比，针尖质量更好，另外扫描隧道显微镜测试结果也表明针尖质量完全符合要求。

Preparation of tips for scanning tunneling microscopy by optimized difference method

Scanning tunneling microscope is a high-resolution surface research instrument, and its tip has an important impact on the image quality. In this study, we proposed a new circuit for overcoming the shortcomings in current popular equipments, such as low success rate and unstable corrosion process. The measuring mechanism of reaction current changed so that the actual voltage between the cathode and anode remained stable during the experiment. Moreover, in order to obtain a sharper tip, the differential circuit wasused to monitor the reaction process which couldbe cut off immediately to avoid overreaction and led to a blunt apex. Finally, we observed the effects of the reaction voltage, the position of cathode ring, the sensitivity of the differential circuit and the electrolyte concentration on the tip quality, and proposed the appropriate reaction parameters. The advantages and disadvantages of the new circuit and the traditional method were also suggested. The results showed that the new circuit wasimproved in stability and quality, which was also proved by the scanning tunneling microscopy test.