A new laser ablation geometry for the production of smooth thin single-layer YBa 2Cu 3O 7− x and multilayer YBa 2Cu 3O 7− x/PrBa 2Cu 3O 7− x films

Abstract

The advantages and results of a new geometry for laser ablation are presented. The laser beam enters the ablation chamber via a computer controlled scanning mirror and is x− y rastered across the target surface. The laser beam hits the target at normal incidence through the ablation plume. The ablation products are allowed to thermalize in a 200 mTorr oxygen atmosphere before being deposited on a heated substrate (750 °C, SrTiO 3, LaAlO 3, yttria-stabilized zirconia) facing 180° to the initial plume direction. This overcomes the problem of molten rocks and blobs ejected from the target being deposited on the substrate and results in very smooth films (± 50 Å for 5000 Å thickness). The high temperature resistivities of YBa 2Cu 3O 7− x were linear with temperature with their extensions passing through zero resistivity at 0 K. Typical T c values of 90–92 K widths were regularly obtained. No oxygen anneal either in situ or post-deposition was required. X-ray analysis shows the films to be c axis oriented. The technique has been extended to the growth of very high quality YBa 2Cu 3O 7− x /PrBa 2Cu 3O 7− x multilayer films. Their X-ray spectra are presented for various thicknesses of the individual layers.