Combining experimental and modelling approaches to understand the expansion of lattice parameter of epitaxial SrTi1-xTaxO3 (x = 0–0.1) films

• Published in: Computational materials science 2023-01, Vol.217, p.111917, Article 111917
• Main Authors: Arya, Mamta, Kumar, Shammi, Hasina, Dilruba, Sen, Raja, Ojha, Sunil, Kumar, Vijay, Som, Tapobrata, Dhar, Sankar
• Format: Article
• Language: English
• Subjects: Density function theory; Doped SrTiO3; Epitaxial growth; Lattice parameter; Thin films
• ISSN: 0927-0256; 1879-0801
• DOI: 10.1016/j.commatsci.2022.111917

[Display omitted] Cubic SrTiO3 is widely used as a model perovskite oxide due to its exotic optical, electronic, magnetic, superconducting, and ferroelectric properties, which are dominantly influenced by its lattice parameter. This paper reports on the experimental observation of Ta5+ dopant-induced expansion of the perpendicular lattice parameter (a⊥) of (001) heteroepitaxial SrTixTa1-xO3 (x = 0–0.1) films grown at substrate temperature (Tg) of 750 °C under 5 × 10-5 mbar oxygen partial pressure (pO2). The experimental results demonstrate the synthesis of very high-quality epitaxial thin films in which almost all the Ta5+ dopants are substituted. However, not all the carriers are activated due to compensating defects. All these films have smooth surfaces and are stoichiometric in compositions. The value of a⊥ increases linearly with increasing Ta or free carrier concentrations. This expansion is modelled via density functional theory (DFT). The influences of three effects are considered in the present modelling: (i) ionic radius of Ta dopant (ii) deformation potential due to hydrostatic strain energy (iii) concentration of free carrier. Further calculations of a⊥ are also performed by considering the influence of substrate and the results overestimate the experimental values by ∼ 1 %. Further experiments on other perovskite systems are required to establish the efficacy of these modelling approaches.