Nanometer level etching and deposition of Bi-Sr-Ca-Cu-O superconducting thin films

Abstract

In situ accurate flux monitoring technique utilizing atomic absorption spectroscopy (AAS) for the molecular beam epitaxy (MBE) growth is described. The AAS signal data are calibrated using the inductively coupled plasma spectroscopic technology. The calibration curves are not influenced by variations of both the substrate temperature and ozone flux rate within the range of MBE growth conditions. SrO and CaO are epitaxially grown on SrTiO<SUB>3</SUB> substrates with RHEED intensity oscillations. This fact becomes another convenient and practically important method for calibrating the AAS data. A method for estimating the ozone flux is also discussed. A gas-laser-etching of Bi-Sr- Ca-Cu-O thin films is carried out by digitally counting an etch process loop. Laser irradiation and NF<SUB>3</SUB> gas-supply are separately made. At a laser fluence range the etch depth is independent of the laser fluence, suggesting that the etching is limited by the amounts of absorption gas molecules. The way how the etch depth depends on the etching loop count is intensively investigated. The depth is saturated after etching of a few loops. The surfaces of the etched area are flattened and smoothened. Possible models about the etch depth saturation and surface flattening are discussed.