Project Overview

Scanning tunneling microscopy is the use of electron tunneling to map and image material surfaces at the atomic level. This is done by bringing a conductive, scanning probe tip—usually made from tungsten—close enough to a material so that electrons from the tip can quantum mechanically tunnel across the gap between the probe and the sample, thus producing a tunneling current that can be measured and used to determine the atomic topography of a material's surface. STMs are composed of a preamplifier circuit that amplifies the tunneling current signal, and a PI controller that uses feedback from the scanner to provide both data on the scanning tip's distance from the sample, and a way to ensure a constant tunneling current by changing the scanning tip's position relative to the sample's topography of the sample. These elements together then provide information on the topography of the sample via the voltage applied to the piezo-driver, which is modulated by the PI controller.

STMs have been built using easily accessible materials in the past; these systems utilize piezo drivers that are used in electric buzzers to position a scanning tip in x, y, and z directions. These systems, however, commonly use disk scanners which are rather noisy despite their lower driving voltage.

Engineering Requirements

• • Resonant frequency of mechanical system should be <1 Hz.

  • Rastering code that provides signal for left-right scanning producing resolution of ~0.01 nm in the ±X and ±Y direction.

  • Noise figure should be <3 nV/√Hz for the amplifier

  • Produce tunneling current in the order of 1 nA, using a precise and low-noise preamplifier.

Marketing requirements

• • • • Device should be inexpensive and easy to use for academic researchers with very minimal knowledge of the device.