Compact coarse approach mechanism for scanning tunneling microscope

We report on the design and fabrication of a coarse approach mechanism, cal led a piezotube walker, based on a piezoelectric tube moving inside a trian gular prism shaped cavity. This walker walks like a six legged insect movin g its legs one by one and then the belly following. The walker works in any orientation from horizontal to vertical and its motion is found to be line ar with the applied voltage above a threshold voltage. A compact scanning t unneling microscope (STM) was fabricated using this approach mechanism. The scanner tube of the STM is mounted on the inside of the walker tube, reduc ing the size of the STM considerably. Topographical images with atomic reso lution were obtained for layered materials like graphite and NbSe2. (C) 200 1 American Institute of Physics.