Gallium ion implantation into niobium thin films using a focused-ion beam

We have implanted 30 keV gallium ions into niobium films 100 Å thick using a focused-ion beam (FIB). The nature of the FIB tool allows the irradiation of a specific, controllable, area of the substrate, from hundreds of square microns down to an arbitrary, user-defined pattern defined by a 70 Å stencil. A sacrificial layer of gold covering the niobium controls the range of the incident gallium ions and prevents the niobium film from sputtering away under bombardment. This article examines the behavior of these films phenomenologically, including information about the changes in transition temperature and resistance of the implanted samples. Also a curious unexplained feature of the resistive transition at implant doses below about 3×10¹⁹ cm^-3 will be presented and discussed.