Scanning tunneling microscopy and spectroscopy at very low temperatures

We discuss recent results and advances in very low temperature scanning tunneling microscopy in superconductors, focusing on the experimental developments that have permitted to extend the present applications of this technique to new materials. We detail the experimental apparatus used and discuss the results and the future possibilities of S-I-S tunneling using a superconducting tip and sample. Further on, we present results on the superconductivity of single gains of MgB2 and compare them with other works. We also discuss recent data on the borocarbide material TmNi2B2C. (C) 2001 Elsevier Science B.V. All rights reserved.