Materials Research Activities

Untitled Document

Erik Lægsgaard

In the summer of 1987, Erik Lægsgaard, prompted by his two colleagues in the Institute of Physics and Astronomy at Aarhus University, Flemming Besenbacher and Ivan Stensgaard, built a scanning tunneling microscope (STM). This instrument has provided a resource for CAMP (Center for Atomic-scale Materials Physics), a research project resulting in a long string of publications that have enjoyed widespread attention.

Interestingly, Lægsgaard was able to build the STM with materials scrounged from the laboratory in weeks. Only three years earlier, there had been widespread distrust of Binnig and Rohrer's STM measurements because of the difficulty of replication. By 1986, and the award of the Nobel Prize, the STM design had simplified considerably, reflecting a decreasing concern with insulation from external influences such as vibration. Lægsgaard and his colleagues demonstrated the surprising feat of atomic resolution without the use of extraordinary insulation, in fact with a mere minimum of insulation.

The Aarhus STM is acknowledged to be of excellent quality, and the Aarhus group has continued to prefer the homegrown variation to the commercial instrumentation for many applications.

In our interview (in Danish only, sorry!), Erik Lægsgaard describes the history of STM research at Aarhus. He relates the production of an STM in the summer of 1987, scrounging materials from idle experiments in the physics lab and reveals some of the mundane requirements: a foam rubber layer as insulation; contacting of electrodes with glue; electronics (adapted from Lægsgaard's previous research on particle detectors); piezo-tubes (scrounged from laser interferometers). For the tip, the Aarhus people simply used bits cut off a platinum-iridium filament using nothing more sophisticated than a wire-cutter. In fact, the expenses for the first STM amounted to a stunning 0 Danish kroners, because everything that went into the STM was scrounged from the lab!

There are now websites for making one's own STM, but a certain tinkering facility is required to follow the instructions. Erik Lægsgaard had the background to do it. He grew up in a rural garage on the island of Funen, finishing an apprenticeship as a car mechanic at the age of 15. He then began an apprenticeship as a radio mechanic, and studied electronic engineering at a polytechnic. He gained employment at Aarhus University in 1965, first in Electronics and then in the Physics Department, where he made particle detectors. In the 1990s, he then joined the faculty.

Lægsgaard is also an enthusiastic radio amateur, and his flair for tuning played itself out in the electronics controlling the scanning mechanism. The Aarhus electronics' noise level is particularly low. His radio background has led to a particularity of the Aarhus system: researchers use head phones while scanning. One quickly learns to recognize, for instance, the sound of atomic resolution. The use of wireless headphones has had the added advantage that pairs of researchers could discuss the measurement on the fly.

Legend: Jeppe Vagn Lauritsen listening to the sound of the tunneling current.

In the interview Lægsgaard also describes the development of the electronics and the software since 1987, along with some of the adaptations for UHV STMs. The impact of computers has been minimal with regard to the actual scanning process, but of course the data processing has improved. Data storage has also changed rapidly in the last 14 years, resulting in the loss of old data that are stored in a form no longer compatible with modern equipment.

This page was written by Arne Hessenbruch and last updated on 19 July 2001.