Dry etching studies of YBa2Cu3O7-δ nm structures at cryogenic temperatures

Abstract

Abstract We report a systematic study about the influence of substrate temperature during dry etching on the superconducting properties in YBa2Cu3O7-δ nanobridge structures. The substrate temperature has been varied between 300 K and 20 K. High energy electron-beam lithography has been used to fabricate submicron bridges between large area contact pads. The linewidth has been varied from 1.5 μm to 200 nm whereas the length has been kept constant at 10 μm. It is shown that LN2 cooling of the substrate is an efficient method to minimize ion beam induced degradation in YBa2Cu3O7-δ nanostructures. Compared to 300 K substrate temperature, an increase in the critical current density jc at 77 K by an order of magnitude is reported for 400 nm wide structures. As a result of further reduced substrate temperature (20 K) during the dry etching process, 200 nm wide YBa2Cu3O7-δ structures have been fabricated with 64.5 K zero resistance temperature.