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 grains of MgB 2 and compare them with other works. We also discuss recent data on the borocarbide material TmNi 2B 2C.