Electron Dynamics in Semiconductors Can Now Measure Using Optical Nanoscopy Laser Beam Tool

Every mobile phone, laptop, and autonomous vehicle contains a tiny semiconductor at its core, whose characteristics and performance are ultimately controlled by free electrons. These electrons can now be measured in a new way that was created by UC Berkeley researchers. This method may help create semiconductor materials and electronics that are more energy-efficient.

According to a report in Nano Letters, scientists have demonstrated a new kind of optical nanoscopy that can measure electron dynamics in semiconductors, a task that has grown more difficult as the demand for ever-smaller and faster-integrated circuits increases. To measure electrons with high resolution, new tools are required because many components of everyday electronic devices are already at the nanoscale.

(Photo: Bethany Clarke / Stringer)
Optical nanoscopy uses laser beams to strike free electrons, scattering light and providing insights into electron distribution and dynamics within semiconductor materials.

Optical Nanoscopy Tool

Professor of mechanical engineering Costas Grigoropoulos, who is also the study's principal investigator, claims that their optical nanoscopy tool combines pump-probe optics and near-field scanning optical microscopy to produce high resolution at both temporal and spatial scales. A variety of semiconductor materials, including silicon, germanium, and gallium arsenide, as well as less common ones like 2D materials and ferroelectrics, can also be used with this technology.

To measure electrons, or energy carriers, at picosecond and nanometer scales, the optical nanoscopy tool combines optical imaging and laser probing technologies. These measurements may reveal information about the distribution and behavior of energy carriers in semiconductor materials, which may affect other characteristics such as energy efficiency.

The study, according to Jingang Li, the lead author and a postdoctoral researcher in Grigoropoulos' Laser Thermal Lab, is a critical first step in examining and further optimizing energy savings for semiconductor-based electronic devices, including mobile phones, LEDs, commercial solar cells, and sensors, following the report from Berkeley Engineering press release.

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Ultrafast Lasers And Lesser Nanometers

As reported by Phys, Li explained that because integrated circuits have a high chip density, the distribution and transport of electrons control both the device's functionality and the generation and dissipation of heat. They will be able to examine the nanoscale thermal control in these densely packed devices thanks to their nanoscopy tool.

Using atomic force microscope (AFM) tips with apex curvatures of less than 30 nanometers and ultrafast lasers, optical nanoscopy can measure the electrons in semiconductors. Researchers illuminate the AFM tip with two laser beams: a pump beam and a probe beam. After a precisely timed delay, the second beam strikes the tip after the first beam has excited electrons in the sample. After that, by examining the second beam's scattered light, it is possible to determine the local information on electron properties.

Li speculates that optical nanoscopy might be used for tasks other than counting electrons in semiconductor materials. He explained that because it is a versatile optical diagnostic tool, it can be used to investigate a wide range of other physical phenomena and functional elements, including phase transitions and data storage. Yoonsoo Rho, Penghong Ci, and other postdoctoral researchers in mechanical engineering are additional co-authors of this study. D. Matthew Eliceiri and Rundi Yang, both students, as well as Junqiao Wu, a professor of materials science and engineering. The Laser Prismatics LLC contributed to this study.