Yuanfang Li (EngSci 1T5)

This summer, I had the privilege of completing a research internship at the National University of Singapore (NUS). While in Singapore, I worked under Dr. Jeroen A. van Kan at the Centre for Ion Beam Applications on improving the control system of the scanning tunneling microscope. The main goal of the project was to stabilize performance of the microscope by reducing internal and external noise. Together with my team mate, Rahul, we were able to accomplish this by improving the noise performance of the integrated circuits controlling the microscope, and eliminating noise from analog circuits by switching over to wireless digital control.

The performance of the integrated circuits was improved largely by replacing the operational amplifier in the circuit with a higher performing one. This was done by first completing a survey of the different amplifiers available on the market, then obtaining samples of the most suitable ones and testing them with the actual circuit to determine which one produced the least amount of noise. Other methods of reducing circuit noise were also attempted, including shielding the circuit in a copper box, but this proved less successful.

To further reduce noise, the analog feedback loop controlling the scanning tunneling microscope was replaced with digital control using a programmable FPGA chassis and two input and output cards. This process involved first testing the noise level of the cards themselves, then programming the chassis to implement the same control loop as the analog circuit. The microscope’s performance was further stabilized by using a router to allow users to control the microscope wirelessly from a computer without connecting it to the chassis.

The combination of improved integrated circuits and wireless digital control allowed us to achieve a stable tunneling current that was an improvement over previous results. In addition, the improved stability of wireless control of the chassis could be applied beyond the microscope to improve the performance of other instruments in the lab, such as the ion beam writer.

Throughout the internship, I was involved in both the theoretical and experimental aspects of the project as I had to research methods of reducing noise, and then apply it to the microscope’s control system. Furthermore, I had the opportunity to work with a variety of instruments, including operating the scanning tunneling microscope itself, and programming the chassis controlling it. The experience taught me many new engineering skills like soldering and block diagram programming, that I will be able to apply in the future to school and work projects.

In addition to the technical aspects of the project, the internship also provided me with experience working within a research team. I was privileged to meet and work with students and professors at NUS, as well as exchange students from other universities, and would like to thank them for all their help. This was a unique experience that not only allowed me to gain a lot of practical experience in electronics and control theory, but also provided me with the opportunity to explore Singapore. Many of the people I met provided me with great suggestions on places to visit and foods to try, allowing me to truly enjoy the Singaporean culture.

My research internship in Singapore was a unique and unforgettable experience. I am extremely grateful to the Department of Engineering Science at the University of Toronto and the National University of Singapore for providing me with this opportunity, as well as all the students and staff at NUS for making me feel so welcome at their university.