Non-contact testing of silicon conductivity
To create electric charges in silicon, researchers shine pulsed laser light onto a sample. One-photon tests using visible light only penetrate a tiny way into a silicon sample — on the order of micrometers (millionths of a meter) or smaller. But the new two-photon tests using near infrared light penetrate much, much deeper into silicon, on the order of millimeters (thousandths of a meter) or longer. The one-photon tests create a lot of electric charge (shown here as pluses and minuses) in a relatively small volume. By contrast, the two-photon test creates far fewer electric charges in a much larger volume.
February 2020 • NIST • https://www.nist.gov/news-events/news/2020/02/how-low-can-you-go-lower-ever • Tagged: Diagrams