Comment on "Epitaxial BiFeO 3 Multiferroic Thin Film Heterostructures"

Abstract

Like Wang et al. (1), we grew BFO films on 50-nm underlayers of SrRuO₃ (SRO) on SrTiO₃ (001) substrates (STO). In addition, we used plain STO and conducting 0.2% atomic Nb-doped SrTiO₃ substrates (Nb-STO). Both BFO and SRO films were grown by pulsed laser deposition with a KrF excimer laser (248 nm, 1 Hz, target-substrate distance = 8cm). BFO films were grown (670°C, 8 Pa O₂, 1.6 J cm^–2) using a Bi-rich target of Bi_1.2FeO₃, because Bi is volatile (6). SRO films were grown (650°C, 9 Pa O₂, 1.7 J cm^–2) using a stoichiometric target. The growth rate for both BFO and SRO was 10 Å/min. After deposition, films were cooled at 5°C/min to 400°C in 40 kPa oxygen, annealed for 1 hour, and then cooled to room temperature at 8°C/min.