Close Approach and Sustained Tunneling Feedback Control in a Scanning Tunneling Microscope Design

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The goal in this research project is to design and implement a low cost scanning tunneling microscope (STM). We are pursuing this goal by using low cost materials, simple construction techniques, and a novel approach to tip actuation using rare earth magnets, hand-wound solenoids, and a single inexpensive piezoelectric stack. Through a combination of very simple hardware and software, we have implemented a close approach system that allows us to acquire electron tunneling consistently. The hardware used to accomplish this consists of a low-cost NXT motor, a piezo stack, and simple inexpensive electronics; the software that we developed is in LabVIEW (LV). After achieving electron tunneling, we maintain it by applying closed loop feedback control techniques using a LV-based proportional-integral-derivative (PID) algorithm. The feedback control allows us to maintain the tunneling current for an extended period of time. In this talk, we will focus on the hardware and software used in both the close approach and feedback control.