NEWLY DEVELOPED LOW-TEMPERATURE SCANNING TUNNELING MICROSCOPE AND ITSAPPLICATION TO THE STUDY OF SUPERCONDUCTING MATERIALS

A newly developed scanning tunneling microscope (STM) capable of opera ting at room temperature, 77 K, and 4.2 K is presented. This compact S TM has a highly symmetric and rigid tunneling unit designed as an inte gral frame except the coarse and fine adjustment parts. The tunneling unit is incorporated into a small vacuum chamber that is usually pumpe d down to 2X10(-4) Pa to avoid water contamination. The fine mechanic adjustment makes the tip approach the sample in 5 nm steps. The coarse adjustment not only changes the distance between the tip and the samp le, but also adjusts the tip to be normal to the surface of the sample . With this low-temperature STM atomic resolution images of Bi-2212 si ngle-crystal and large-scale topographies of a YBa2Cu3O7 thin film are observed at 77 K.