An Ambient Air Scanning Tunneling Microscope to Study the Surfaces of Thin Metal Films

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Wilson, Joshua C.
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Houghton University
An ambient–air scanning tunneling microscope (STM) is being built at Houghton University to study the crystal growth and transformation of thin metal films. The STM operates by maintaining a constant current between a piezoelectrically–controlled scanning probe and the thin metal film sample while recording the height of the probe relative to the sample stage. This current is produced when electrons from the sample quantum tunnel through the ~10-10 m air gap to the probe, aided by a small bias voltage of ~-1 V applied to the sample. In order to achieve a tunneling gap of this size, the STM uses stepper motors to perform a rough approach of the probe to the sample. The STM is suspended on a dual-stage vibration isolation system which uses springs with eddy current damping to protect the STM from background noise. The STM is controlled by a user interface written in Processing and a Teensy 4.1 microcontroller via Arduino, along with a control circuit. The data collected by the STM are used to create an intensity plot that will act as an atomic resolution “image” of the film surface. All hardware, electronics, and programs have been completely and successfully tested.
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