A variable-temperature ultrahigh vacuum scanning tunneling microscope

A variable-temperature ultrahigh vacuum (UHV) scanning tunneling microscope (STM) was designed and tested. Design details and initial results are pres ented. The STM is directly attached to the cold face of a continuous flow c ryostat which is mounted into a two-chamber UHV system. A significant advan tage of this system in comparison to many others is, that samples can be co oled down to base temperature of 6.5 K within very short times of below 2 h . This feature not only increases the potential sample throughput, it also allows to cycle the sample temperature within the regime below 20 K without losing track of given sample locations. The instrument was tested by imagi ng Au layers on graphite. The vertical stability at low temperature was fou nd to be below 3 pm. Images recorded at 6.5 K show crystalline Au islands a nd the Au(111)22x root3 reconstruction with atomic resolution. Using a resi stive heater, the sample temperature was adjusted between 6.5 and 20 K. Aft er an equilibration time of 15 min, the displacement due to the temperature change remained below 150 nm. Scanning tunneling spectroscopy on Au(111) g rains resolves the Au(111) surface state. (C) 2001 American Institute of Ph ysics.