Electron tunnelling and critical current behaviour of patterned Y1Ba2Cu3O7 − δ films

Abstract

We report on point contact tunnelling experiments on preferentially c oriented Y1Ba2Cu3O7−δ (123) films deposited onto (100) SrTiO3 substrates using an ultra-high vacuum (UHV) triple electron-gun system with BaF2, yttrium and copper as source materials. The films were coated with a thin silver layer and annealed at 450°C. A niobium point was then carefully brought into contact with the surface, which was investigated by electron tunnelling. Using 10 GHz radiation we identified microwave-induced current steps in the current-voltage characteristic. Also, there was a strong decrease in Josephson current on application of a magnetic field. Moreover, UHV films were patterned into strips as narrow as 10 μm using a reactive ion etching technique. Critical current densities of about 106 A cm−2 at 20 K were obtained, which is an order of magnitude larger than for sputtered films, but smaller than for UHV laser-patterned thinner films.