Development Of Tantalum Based Superconducting Tunnel Junction

Detectors For X-Ray Absorption Spectroscopy *

A thesis submitted to the faculty of
San Francisco State University
in partial fulfillment of
the Requirements for
the degree


Master of Science
in
Physics


by
Faustin Carter
San Francisco, California
August 2009


Superconducting tunnel junction (STJ) X-ray detectors can offer both the energy resolution and the fast count rate necessary to measure the energies of individual photons in fluorescence-detected X-ray absorption spectroscopy at a synchrotron.

The SFSU Cryogenic Electronics Group has developed a full-wafer fabrication process for Ta-based STJ X-ray detectors and has carried out a set of experiments to control the structural phase, optimize the film stress and uniformity, and determine the critical temperature (Tc) values for Ta films. Constructing STJs from Ta (rather than from the more traditional niobium) offers higher efficiency due to better X-ray absorption in the top electrode, which reduces the spectral-line splitting artifact present in Nb-based devices. This thesis discusses the fabrication challenges that arise from using Ta and presents DC characteristics of initial devices.

(* A copy of this thesis, in PDF format, is viewable by clicking on this link.)



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Updated 19 April 2013