Ballistic electron emission microscopy or BEEM is a technique for studying ballistic electron transport through a variety of materials and material interfaces. BEEM is a three terminal scanning tunneling microscopy (STM) technique that was invented in 1988 at the

Jet Propulsion Laboratory The Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center in the City of La Cañada Flintridge, California, United States. Founded in the 1930s by Caltech researchers, JPL is owned by NASA an ...

Pasadena, California Pasadena ( ) is a city in Los Angeles County, California, northeast of downtown Los Angeles. It is the most populous city and the primary cultural center of the San Gabriel Valley. Old Pasadena is the city's original commercial district. I ...

by L. Douglas Bell,

Michael H. Hecht Michael H. Hecht is a research scientist, associate director for research management at the Massachusetts Institute of Technology's Haystack Observatory, and former deputy project director of the Event Horizon Telescope. He served as lead scie ...

, and William J. Kaiser. The most popular interfaces to study are metal–semiconductor

Schottky diode The Schottky diode (named after the German physicist Walter H. Schottky), also known as Schottky barrier diode or hot-carrier diode, is a semiconductor diode formed by the junction of a semiconductor with a metal. It has a low forward voltage ...

s, but metal–insulator–semiconductor systems can be studied as well. When performing BEEM, electrons are injected from a STM tip into a grounded metal base of a Schottky diode. A small fraction of these electrons will travel ballistically through the metal to the metal– semiconductor interface where they will encounter a

Schottky barrier A Schottky barrier, named after Walter H. Schottky, is a potential energy barrier for electrons formed at a metal–semiconductor junction. Schottky barriers have rectifying characteristics, suitable for use as a diode. One of the primary char ...

. Those electrons with sufficient energy to surmount the Schottky barrier will be detected as the BEEM current. The atomic scale positioning capability of the STM tip gives BEEM

nanometer 330px, Different lengths as in respect to the molecular scale. The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm) or nanometer (American and British English spelling differences#-re ...

spatial resolution. In addition, the narrow energy distribution of

electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no kn ...

s tunneling from the STM tip gives BEEM a high energetic resolution (about 0.02 eV).

References

{{DEFAULTSORT:Ballistic Electron Emission Microscopy Scanning probe microscopy American inventions Jet Propulsion Laboratory