The resistivity and plasmon energies of bcc and A-15 superconductors

Abstract

Measurements have been made of the plasmon energies in Nb, bcc Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-y</inf> Ti <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</inf> alloys as a function of y, and Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</inf> Ge <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> samples as a function of x. The samples investigated are 1 micron thick film samples synthesized by selectively thermalized trisputtering. Samples of these systems can be synthesized in an amorphous as well as a crystalline state. Measurements of the plasmon energies have been made by electron energy loss spectroscopy. The measurements reported here were made with a primary electron beam energy of 80eV. For pure Nb a plasmon energy of 9.65±0.10eV was measured. For A-15 Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Ge a value of 4.91 ± 0.08eV was measured. For Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Ge from our resistivity data combined with this plasmon energy we calculate a value of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">h\tau\min{ep}\max{-1} = 0.148\pm0.017</tex> eV for the electron phonon relaxation time. The intensity of the plasmon peak as a function of x and y was observed to correlate with the high T <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> composition region. Samples have been characterized by T <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> , resistivity, X-ray diffraction, X-ray fluorescence, and Auger measurements.