PrBa2(Cu0.8Al0.2)3O7 Thin Film Surface Smoothing by Ar-Cluster Ion Beam Bombardment
ABSTRACT Al doped PrBa2Cu 3O7 epitaxial thin film is an excellent insulating material for oxide superconducting junction application. The surface of such films grown at high temperature is usually very rough and requires smoothing during device fabrication. A gas cluster ion beam is a good tool for smoothing the surface down to the sub-nanometer level. In this paper, PrBa2(Cu0.8Al0.2)3O7 thin films of different thickness grown by Pulsed Laser Deposition (PLD) were irradiated with a 20 keV Ar-cluster ion beam. The average size of the Ar-clusters was about 3000 atoms per cluster. A film thickness varying from 48nm to 920 nm with corresponding initial roughness of 2 nm to 10 nm was studied. The roughness was gradually reduced with increasing cluster ion dosage, reaching an ultimate of 0.7 nm. For a sample of average sputtering yield, surface damage and the annealing effect after smoothing were also studied.