An ultrahigh vacuum cryogenic scanning tunneling microscope with tip and sample exchange

An ultrahigh vacuum, cryogenic scanning tunneling microscope (STM) has been developed for imaging and current-voltage spectroscopy. Design details and results from initial studies are presented. The microscope design is based on the Besocke "beetle" style STM with some significant modifications. In particular, the placement of the tip and sample have been interchanged to facilitate in-vacuum transfer of tips and samples. The STM operates in a cryostat submerged in liquid helium or liquid nitrogen. Imaging of the 22 x root 3 reconstruction of the Au(111) surface and atomic resolution of graphite are demonstrated. A current versus voltage spectrum showing Coulomb charging features and level quantization in a 29000 amu Au nanocrystal is also presented to show the spectroscopic capability of the instrument. (C) 1999 American Institute of Physics. [S0034-6748(99)01801-8].