Thermoelectric Charge Imbalance in Superconducting Aluminum and the Development of a Scanning Tunneling Microscope

摘要

Two experiments in solid-state physics have been performed, the observation of the superconducting fountain effect and the development of a Scanning Tunneling Microscope. In the first experiment, the quasiparticle transport current induced in a superconducting aluminum film by a temperature gradient has been measured by means of the spatially decaying charge imbalance generated near the end of the sample, where the current is divergent. The magnitude and decay length of the charge imbalance are in good agreement with the predictions of a simple model that takes into account the nonuniformity of the temperature gradient. The inferred value of the thermopower in the superconducting state agrees reasonably well with the value measured in the normal state. Measurements of the decay length of the charge imbalance induced by current injection yield a value of the inelastic relaxation time tau/sub E/ of about 2 ns, which is substantially smaller than that obtained from other measurements for reasons which are not completely understood. In the second experiment, a Scanning Tunneling Microscope, an instrument first developed at IBM Zurich, has been developed at U.C. Berkeley in order to study surface structure. On uncleaned gold surfaces, a typical vertical resolution of 0.1 A and a lateral resolution of 20 to 30 A have been achieved, with one instance of lateral resolution under 10 A. 85 references, 36 figures. (ERA citation 10:009293)