We present Nb thin films deposited in-situ on GaAs by combining molecular
beam epitaxy and magnetron sputtering within an ultra-high vacuum cluster. Nb
films deposited at varying power, and a reference film from a commercial
system, are compared. The results show clear variation between the in-situ and
ex-situ deposition which we relate to differences in magnetron sputtering
conditions and chamber geometry. The Nb films have critical temperatures of
around 9K. and critical perpendicular magnetic fields of up to
Bc2=1.4T at 4.2K. From STEM images of the GaAs-Nb
interface we find the formation of an amorphous interlayer between the GaAs and
the Nb for both the ex-situ and in-situ deposited material.Comment: 12 pages paper, 9 pages supplementary, 6 figures paper, 7 figures
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