VERSATILE SYSTEM FOR POINT CONTACT CONDUCTANCE SPECTROSCOPY

A versatile system has been designed and constructed which is being used for point contact and tunnelling studies. A cryostat capable of going down to 1.5 K is equipped with a differential screw mechanism and a piezoelectric tube which help to make the point contact junctions in liquid helium. An attractive feature of this cryostat is the movable multi-tip arrangement. This enables the construction and study of four different point contact junctions under the same conditions in a single experiment. A simple analogue circuit built with low cost integrated circuits and components is used to measure the differential conductance, dI/dV, directly. This system has been used for studying electron transport across metal-metal and normal metal-superconductor microcontacts. Point contact tunnelling measurements have also been carried out on high T(c) oxide superconductors to determine the superconducting gap parameter, DELTA.