News
Single molecules by STM Although numerous designs for scanning tunneling microscopes (STMs) are capable of low-temperature measurements, many of these systems still suffer from problems such as cryostat vibrations or mechanical instabilities caused by temperature cycling of components. Wilson Ho and colleagues at Cornell University introduce a variable-temperature ultrahigh-vacuum STM design that offers stability comparable to that of a fixedtemperature STM
The design calls for the STM to be suspended by three swings from the cold tin of a continuous flow cryostat Two
radiation shields completely surround the unit. The unit provides temperatures from 8 to 350 K. Temperature drift at 8 K is typically less than 0.01 K per day. Moreover, widi the feedback loop off, the tip-sample drift is approximately 0.001 A/min at 8 K. The design allows for in situ dosing and photon irradiation of the sample surface, and, say the designers, the STM is simple and inexpensive to build. The researchers demonstrated the STM's capabilities by imaging molecules and atoms on surfaces moving an atom across a surface and performing inelastic electrontunneline
Schematic of the variable-temperature STM. (Adapted with permission. Copyright 1999 American Institute of Physics.)
on a sinde acetvlene molecule on a Conner surface (Ra> SW It>
