A DUAL TUNNELING-UNIT SCANNING TUNNELING MICROSCOPE

A regular crystalline lattice has a high potential of being used as a well-defined, universal reference scale in the metrological application of scanning tunneling microscopes (STMs). A dual tunneling-unit (DTU) STM, incorporating one XY scanner and two Z scanner with tips was developed to check the feasibility of the “crystal-reference” STM. Basic ideas and problems of substitution measurement and crystal-reference XY positioning table are discussed. With the scope of developing a robust and reliable positioning table, software and circuitry design were carried out on two methods of tip-and-target XY position lock control, and one method of servo tracking of atomic arrays. Promising simulation results were obtained as to the noise tolerance of the controls. A successful application of an impact force driven rough positioning mechanism for coarse tip approach is also introduced. Its performance, operating principles and structure are extremely high vacuum oriented. © 1990, American Vacuum Society. All rights reserved.