  We present a method for in-situ tuning the critical current (or switching
current) and critical temperature of a superconducting nanowire using high bias
voltage pulses. Our main finding is that as the pulse voltage is increased, the
nanowires demonstrate a reduction, a minimum and then an enhancement of the
switching current and critical temperature. Using controlled pulsing, the
switching current of a superconducting nanowire can be set exactly to a desired
value. These results correlate with in-situ transmission electron microscope
imaging where an initially amorphous nanowire transforms into a single crystal
nanowire by high bias voltage pulses.
