NEW DESIGN OF A VARIABLE-TEMPERATURE ULTRAHIGH-VACUUM SCANNING TUNNELING MICROSCOPE

We present the design of a variable-temperature ultrahigh vacuum (UHV) scanning tunneling microscope which can be operated between 20 and 40 0 K. The microscope is mounted directly onto the heat exchanger of a H e continuous flow cryostat without vibration isolation inside the UHV chamber. The coarse approach is performed with an inertial slider driv en by the same piezo tube that is also used for scanning. The performa nce of the instrument is demonstrated by two different kinds of measur ements: First we show topographic images of close packed metal surface s with atomic resolution. Then, we present results from scanning tunne ling spectroscopy measurements on WSe2 under illumination at variable temperatures. (C) 1998 American Institute of Physics. [S0034-6748(98)0 2004-8].