High-quality BaTiO3 epitaxial growth on GaAs (001) substrate by novel SrTiO3/Ti2.5O3 buffer layers
Abstract
Perovskite ferroelectric BaTiO3 material showed promising application in the photovoltaic field due to its positive polarization enhanced open voltage with ferroelectric modulation. Achieving perfect interfaces between the multi-layers based on BTO film was still unresolved. Therefore, we developed the bottom buffer layers SrTiO3/Ti2.5O3 films deposited on GaAs for reducing the lattice mismatch between the epitaxial oxide (BTO) GaAs via PLD system. The out-of-plane epitaxial relationship of this heterostructure was [110]BaTiO3//[110]SrTiO3//[010]Ti2.5O3//[001]GaAs and the in-plane epitaxial relationship was determined to be [110]BaTiO3//[110]SrTiO3//[100]Ti2.5O3//[110]GaAs from RHEED and XRD results. In addition, we found that the inter-diffusions of Ga and As atoms from GaAs substrate to oxides films were prevented greatly by the SrTiO3/Ti2.5O3 passivation layer. Using the Gibbs free energies of formations equations, we explained that the Ga atoms couldn’t diffuse through Ti-oxides at Ti2.5O3/GaAs interface. Our work provided an effective measurement to develop the BTO application in the photovoltaic field.