Cryogenic scanning tunneling microscope for quantum dot spectroscopy

We have designed and fabricated a cryogenic scanning tunneling microscope for probing lithography defined nanometer-scale devices. The piezoelectric double tube is capable of scanning an area up to 22 mu mx22 mum, while maintaining atomic resolution. In addition, the sample mount has a 5 mmx4 mm traveling range. Most importantly, the system is compact and, as a result, it can be inserted into the bore of a superconducting magnet. In this work, we demonstrate a unique application of scanning tunneling system, i.e., the scanning tip is in direct contact with the sample. The spectroscopic information therefore reflects the true characteristics of the devices under test, unlike the typical case where the tunneling barrier through vacuum imposes a large series resistance, on the order of 10(9) Omega. The design as well as the operation of this compact scanning tunneling microscope is described. (C) 2001 American Institute of Physics.