Photoresponse of laser modified high-T_c superconducting thin films

The discovery of high critical temperature (Tc) superconductors has spawned an extensive research effort to understand and apply these new materials. One potentially promising area is in microelectronics. High quality superconducting thin films on a variety of substrates have been demonstrated by several authors. However, useful application of these thin films requires subsequent processing to fabricate microelectronic structures. These structures can range from relatively simple superconducting lines for interconnects to as yet undiscovered electronic devices. In this paper, we present our work on the use of a focused laser beam to modify the transport properties of a superconducting thin film. By placing the film in a vacuum chamber and scanning a focused Ar+ laser beam normal to the surface, we can selectively remove oxygen from the film on a micron scale. The resulting transport properties reveal a reduced Tc and critical current density (Jc). By monitoring the room temperature electrical resistance, one can control the degree of oxygen removal which allows one to modify the film properties from metallic-like to semiconducting-like. This technique shows promise for forming device structures based upon a superconducting-semiconducting-superconducting geometry. Current progress towards the realization of a fast photodetector fabricated by this technique will be discussed.