SCANNING TUNNELING MICROSCOPE WITH CONTINUOUS-FLOW CRYOSTAT SAMPLE COOLING

We have constructed an ultrahigh vacuum scanning tunneling microscope (STM) for operation in the temperature range 20-300 K. The design cons ists of a vibration isolated sample holder mounted on a continuous flo w cryostat. By rotation and linear motion of the cryostat, the sample can be positioned in front of various surface preparation and analysis instruments contained in a single vacuum chamber. A lightweight beetl e-type STM head is towered from the top onto the sample by a linear ma nipulator. To minimize helium convection in the cryostat, the entire v acuum system, including a liquid helium storage Dewar, can be tilted b y a few degrees perpendicular to the cryostat axis, which improves the operation. The performance of the instrument is demonstrated by atomi cally resolved images of the Pd(111) surface and adsorbed CO molecules . (C) 1997 American Institute of Physics.