Researchers Identify Electronic Activity Previously Invisible to Electron Microscopes

Researchers Identify Electronic Activity Previously Invisible to Electron Microscopes

Researchers from University of California, Los Angeles developed a new imaging technique that produces a topographical map of electron flow between two electrodes

Electronic chips that are used in various electronic gadgets are made in semiconductor fabrication plants. These plants use powerful transmission electron microscopes that can observe physical structures that are smaller than a billionth of a meter. However, these microscopes cannot observe electronic activity that makes the devices function. Now, a team of researchers from University of California, Los Angeles (UCLA) and University of Southern California developed a new imaging technique that enables to watch and understand the electronic activity inside working devices. The research led by Chris Regan, UCLA professor of physics and astronomy and a member of the California NanoSystems Institute was published in the journal Physical Review Applied on October 29, 2018.

The new method is capable of describing details that traditional approaches with electron microscopes fail to capture. Moreover, the method also reveals electronic states within a sample, an achievement previously impossible with such microscopes. Beams of electrons are used in electron microscopes to observe an object. The team paired a Scanning Transmission Electron Microscope (STEM) and electron-beam induced current imaging known as EBIC imaging. An amplifier in EBIC imaging is used to measure the electrical current in a sample that are exposed to a microscope’s electron beam. This technique was first demonstrated in the 1960s and is used for showing the electric field built into certain devices such as solar cells.

The team combined both the standard scanning microscope images and EBIC images to examine a simple pair of electrodes. The EBIC images demonstrated previously unseen resolution and contrast and highlighted the electrode that was receiving current and produced a detailed map of the electrodes’ conductivity. To understand the mechanism in the electrodes, the team used two amplifiers to record two EBIC measurements and found that EBIC imaging captured weak signals from secondary electrons. Such sensitive measurements enabled the team to visualize location of electrons along with the spots of their absence.

Emily Sanders

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