Thin films in ternary Bi–Mn–O system obtained by pulsed laser deposition

We have explored the influence of deposition temperature and the deposition rate on the growth of the ternary Bi–Mn–O system onto (001) SrTiO3 substrates by pulsed laser deposition. The studies were performed with a fixed oxygen pressure of 10Pa (0.1mbar) and substrate temperatures between 600 and 680°C. The films were obtained from non-stoichiometric targets with 10 and 15% Bi excess in order to compensate for Bi volatility. The fact that the compound is metastable together with the high volatility of Bi induces different Bi and Mn oxides apart from BiMnO3. Stabilisation of epitaxial BiMnO3 is therefore very elusive and only in a narrow temperature window around 630°C the presence of spurious phases is reduced to traces. X-ray diffraction results reveal a correlation between the Bi–Mn–O compounds and the deposition temperature. Reciprocal space maps show that the BiMnO3 grows completely strained on SrTiO3 substrates. The unit cell has a reduced volume, which could be due to the presence of Bi vacancies. The surface of the films is rough, but they flatten when the films are obtained at lower deposition rates.