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Ballistic Electron Emission Microscopy
Ballistic electron emission microscopy (BEEM) is a three terminal STM technique that can measure the Schottky barrier height between a metal and semiconductor. It can also measure carrier transport through materials and material interfaces with nanoscale resolution. It is an ideal technique to study the nanoscale fluctuations in the electrostatics of buried interfaces that have high technological relevance.
In BEEM, a STM tip is used to inject hot electrons into the metal layer of a Schottky diode while the current transmitted into the semiconductor is recorded. If injected electrons travel through the metal film without scattering; and if the electrons carry enough perpendicular momentum to overcome the Schottky barrier the electrons are collected as BEEM current. BEEM probes the electrostatics of the buried metal-semiconductor interface by varying the injected carrier energy and tip location with meV energy resolution (~0.02 eV) and nanometer spatial resolution, respectively. This technique has been used to measure the Schottky barrier height of many different metal/semiconductor interfaces