Modern energy, communication, and many other technologies depend on semiconductors. Since many years ago, scientists have been studying how to modify semiconductors’ underlying nanostructure to enhance device performance.
Researchers from the University of Tsukuba and their collaborator UNISOKU Co., LTD. have now created a simple-to-use time-resolved scanning tunneling microscope (STM) that can measure the motion of electrons in nanostructures with high temporal and spatial resolution. This method will be extremely useful for improving the performance of nanostructures.
The dynamics of charge carriers determine how current flows through semiconductors and, consequently, how well they operate. These dynamics can happen very quickly. Their dynamics, for instance, maybe 10 billion times quicker than the millisecond range of an eye blink. The most cutting-edge and essential technique for monitoring and visualizing these dynamics in semiconductors at the moment is optical pump-probe (OPP) STM.
However, today’s imaging and measurement technologies must be simplified for non-specialists to understand. Data collection and interpretation require unique methods. Consequently, the researchers wanted to examine this study’s ease of use and operation.
“OPP STM is a crucial technique for determining photo-induced charge carrier dynamics in nanostructures, but it still needs technical development to fulfill the demands of ultrafast observations,” according to senior author Professor Hidemi Shigekawa. “We explored ultrafast carrier dynamics in a typical semiconducting material because of our modifications to OPP STM,” he added.
The researchers describe some particularly remarkable methods that improved the functionality of the created system. They created a steady optical system and added a device to electronically control the laser oscillation and the interval between the pump and probe lights. Using this simple setup, they measured ultrafast charge carrier dynamics on gallium arsenide surfaces.
They also successfully used their method to link charge carrier dynamics to defects like step edges and terraces. This correlation was made possible in part by the imaging’s high level of stability, which allowed it to be carried out on a stable light spot position for 16 hours.
According to the researchers, this discovery will benefit areas like photocatalysis and ultrafast optical communication technology. The user-friendly way of connecting the underlying nanostructure of materials to matching photo-electrical properties will deliver the essential knowledge required for enhancing semiconductor device functionality.
By examining the nanostructure-function relationships of semiconducting materials like gallium arsenide and low-dimensional materials, this work successfully increased the usability of OPP STM. The basic experimental approach used by the researchers can benefit scientists working in various sectors by enhancing the photo-electrical performance of devices like integrated circuits and light-emitting diodes used in ultrafast optical communication technologies. By adjusting the pulsed laser’s wavelength and temporal breadth, the performance of time-resolved OPP STM can be further enhanced, and significant advancements are anticipated.
