Construction of an Inexpensive Scanning Tunneling Microscope for Undergraduate Laboratories

Our goal is to produce an inexpensive, room-temperature, atmospheric-pressure scanning tunneling microscope (STM) with atomic resolution. Our prototype uses slip-stick motion for coarse approach to the surface to be imaged. Motion of the tip is accomplished with four flat piezoelectric translators that provide both z-motion (slip-stick and feedback control) as well as the x-y scanning motion. Maximum x-y scan range is estimated and measured to be approximately 1.7 $\mu $m x 1.7 $\mu $m and the fine z-motion range is estimated to be about 570 nm. Control of the x-y motion is done with a microcontroller containing two 16-bit DACs (digital to analog converter). The z-motion is driven by an analog loop that amplifies the tunneling current and then drives the inner electrode of the piezo translators. The cost of our prototype is currently under {\$}300 and we hope to keep it very affordable for high school and college teaching laboratories.