Growth of fcc metals on lead sulphide: A K Green et al,J Vac Sci Technol, 8 (1), Jan/Feb 1971, 165–170

Abstract

Recent advances in artificial tunneling barriers have resulted in excellent tunnel junctions on several materials whose native oxide are of poor quality. Among the high Tc A15 compounds tunneling α2F(ω) data are now available for Nb3Sn, Nb3Al and Nb3Ge. Among B1 compounds there have been no published α2F(ω) results. Since this is another class of high Tc materials, the contrast would be interesting.This paper will give the first tunneling α2F(ω) spectrum for the B1 compound NbN. The spectrum show two large phonon peaks at energies of 13 meV and 47 meV. The λ value of 1.46±0.10 along with the 2Δ/kBTcof 4.25 show this to be a strong coupled material.In addition, we will present α2F(ω) as a function of composition for A15 VSi, comparing it with previously measured A15 compounds. Here in V3Si unlike the other A15 compounds measured, there is no evidence of mode softening which had been presented as an explanation for the high Tc's in the A15 compounds. Also unusual for the A15 compounds previously measured by tunneling, is that V3Si remains weak coupled as silicon concentration increases. Both the λ value (remaining about 1.0) and the sΔ/kBTc of about 3.5 show this.