Read about our latest work in the AIP Virtual Journal

Facilities Three ultra high vacuum compatible low temperature scanning tunneling microscopes operational down to 4K have been developed at the Institute. All three machines are connected with their own mini MBE sample fabrication chamber equipped with standard surface analytical instruments. Each machine is housed in a separate acoustic and RF screened room and has its own unique capability. The Dual Probe STM This machine contains two independent STMs. The corse positioning of the two STMs is provided by five specially designed PZT steppers with an embedded position sensor of sub-micron resolution. These sensors make it convenient to manipulate and reposition two STM tips with respect to one another. The STMs are cooled by a home-made vapor shield He cryostat which has a remarkable hold time of 48 hours for 2.5 liters of He. High Magnetic Field STM In this machine, two independent STMs are placed in a high magnetic field ( up to ~ 9 Tesla ) generated by a set of superconducting (SC) coils. The STM has its own He cryostat to avoid the bubbling noise of the SC magnet. The sample is loaded through a side-entry port and the STM can be rotated to yield a 2D vector field with only one set of split SC coils. We use the same type of PZT motors developed for the above dual probe STM. Active Feedback STM This machine also contains two STMs with one functioning as a noise sensor so that its signal is fedback with an opposite phase to the second STM for noise cancellation. Special measures are taken so that the two tips have a similar and in-phase mechanical response. This machine will be ideal for high resolution scanning tunneling spectroscopy.