THz-STM enables scientists to image electron behaviour at extremely rapid timescales and enhanced how that behaviour changes between distinct atoms. “We can essentially zoom in to observe very swift procedures with atomic accuracy and over super-fast time scales,” says Vedran Jelic, Ph.D. student at the University of Alberta and head author on the novel research.
“THz-STM offers us with a novel window into the nanoworld, enabling us to explore ultra-fast procedures on the atomic scale. We are talking a picosecond or a millionth of a second. It is something that has never been done before.”
Jelic and his associates used their scanning tunnelling microscope to capture images of silicon atoms by raster scanning a very sharp tip across the surface and recording the tip height as it follows the atomic corrugations of the surface. While the original STM can estimate and manipulate single atoms, for which its creators earned a Nobel Prize in 1986, it does so using wired electronics and is ultimately limited in speed and thus time resolution.
Modern lasers release very short light pulses that can estimate an entire range of ultra-fast procedures, but usually over length scales limited by the wavelength of a light at hundreds of nanometres. Much effort has been expended to combat the limitations of combining ultra-fast lasers with ultra-small microscopy. The University of Alberta researchers addressed these limitations by working in a unique terahertz frequency range of the electromagnetic spectrum that enables wireless implementation. Usually, the STM required an applied voltage in order to operate, but Jelic and his associates are able to drive their microscope employing pulses of light instead. Such pulses occur over really fast timescales, which implies the microscope is able to see truly fast events.
By inculcating the THz-STM into an ultra-high vacuum chamber, free from any external contamination or vibration, they are able to precisely position their tip and maintain a perfectly clean surface while imaging ultrafast dynamics of atoms on surfaces. Their next step is to associate with fellow substance scientists and image a range of novel surfaces on the nanoscale that may one day revolutionize the efficiency and speed of current technology, ranging from solar cells to computer processing.
“Terahertz scanning tunnelling microscopy is opening the door to an unexplored regime in physics,” concludes Jelic, who is studying in the Ultrafast Nanotools Lab with University of Alberta lecturer Frank Hegmann, a world expert in ultra-fast terahertz science and nanophysics.
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