Pulsed laser deposition and nanometer scale characterization of YBa 2Cu 3O 7−δ thin films by scanning probe methods

Abstract

Scanning probe methods (SPM) are applied to study YBa 2Cu 3O 7−δ (YBCO) thin films grown on SrTiO 3(100) substrates by pulsed laser deposition (PLD). Prior to deposition the surface of the SrTiO 3 substrates is investigated by scanning force microscopy (SFM). The misorientation of the substrates as determined from SFM images is less than 0.2° off the (100) plane. Since the misorientation of the substrates varies from wafer to wafer a special half-shadow technique is applied yielding YBCO thin films with a gradient in thickness in order to study the growth morphology as a function of film thickness by scanning tunneling microscopy (STM). At a coverage of less than one YBCO monolayer we observe by STM the nucleation of YBCO islands at SrTiO 3 steps. Up to a film thickness of about 40 nm two-dimensional islands are spreading whereas at larger film thickness growth hills are observed.