Visualizing atomic processes using real-time scanning tunneling microscopy

Scanning Tunneling Microscopy (STM) is a technique for imaging surfaces at the atomic level. The ultra-high resolution has made STM essential in many fields, but one major drawback has been how long it takes to produce an image. A typical STM image takes on the order of 100 seconds or more to produce, which makes STM ineffective for any dynamic analysis.

Gura et al. reduced this time down to about 8 milliseconds per image, thanks to a combination of high-speed electronics and a spiral scan pattern. Their high-speed STM is capable of visualizing dynamic atomic processes.

“With this project, we wanted to bridge from simple imaging into the area of resolving time periods over several orders of magnitude to study the actual motion and dynamic behavior of atoms,” said author Markus Heyde.

The team combined several innovations to reduce the scanning time, most importantly an innovative spiral scan pattern. Traditional STM scans feature a horizontal raster scan pattern that results in the scanning tip passing over each atom two or four times per scan. The spiral scan reduces the number of passes and eliminates sudden speed or direction changes.

The result is an STM scan that can image atoms as they move in real time. The researchers tested their innovation on diffusing atomic oxygen and observed a single oxygen atom moving on millisecond time scales.

“The next steps to take are to write automated software routines in order to track changes and motion events in our data,” said author Florian Kalaß.

Source: “Spiral high-speed scanning tunneling microscopy: Tracking atomic diffusion on the millisecond timescale,” by Leonard Gura, Zechao Yang, Matthias Brinker, Florian Kalaß, William Kirstaedter, Patrick Marschalik, Heinz Junkes, Markus Heyde, and Hans-Joachim Freund, Applied Physics Letters (2022). The article can be accessed at https://doi.org/10.1063/5.0071340 .