Volume 86, Issue 1, 01 July 1999
Index of content:
- DEVICE PHYSICS (PACS 85)
Explicit Green’s function of a boundary value problem for a sphere and trapped flux analysis in Gravity Probe B experiment86(1999); http://dx.doi.org/10.1063/1.370775View Description Hide Description
Magnetic flux trapped on the surface of superconducting rotors of the Gravity Probe B (GP-B) experiment produces some signal in the superconducting quantum interference device readout. For the needs of GP-B error analysis and simulation of data reduction, this signal is calculated and analyzed in this article. We first solve a magnetostatic problem for a point source on the surface of a sphere, finding the closed form elementary expression for the corresponding Green’s function. Second, we calculate the flux through the pick-up loop as a function of the source position. Next, the time dependence of a source position, caused by rotor motion according to a symmetric top model, and thus the time signature of its flux are determined, and the spectrum of the trapped flux signal is analyzed. Finally, a multipurpose program of trapped flux signal generation based on the above results is described, various examples of the signal obtained by means of this program are given, and their features are discussed. Signals of up to 100 fluxons, i.e., 100 pairs of positive and negative point sources, are examined.
86(1999); http://dx.doi.org/10.1063/1.370776View Description Hide Description
The effect of using bilayer Ni/Al-1%Cu or Co/Al-1%Cu metallization stacks with regard to hillock formation is investigated in this study and compared to hillock suppression capabilities of Al-1%Si and Al-1%Cu single layer films and Ti/Al-1%Cu bilayer metallization stacks. Various heat treatments during and immediately after depositions were used to study the resistances of different metallization stack specimens to hillock formation. The densities and sizes of hillocks were characterized using scanning electron microscopy and atomic force microscopy, while interfacial reactions between the transition metal layer and Al-1%Cu in the metallization stack were examined using glancing angle x-ray diffraction. Resistivities of the bilayer metallization stacks were characterized using conventional four-point probe measurements. Our studies indicate that metallization processes involving bilayer metallization stacks of nickel and cobalt with Al-1%Cu are more robust compared to those involving titanium with Al-1%Cu. The mechanism of hillock formation is analyzed in light of intermetallic compound formation and stress-strain considerations.