(151g) Ab Initio study of the Electronic and Optical Properties of Lanthanum-Doped and Magnesium-Doped Strontium Titanate Structures for Advanced Gas Sensing Applications

The prototypical perovskite oxide strontium titanate (STO) has garnered significant research interest for its relevant electronic, transport, structural, and optical properties that endow the material with a wide range of potential applications. Of particular interest is the tunability of its electronic and optical properties; the incorporation of dopants and defects into the bulk structure of STO has been shown to alter its electronic band gap and dielectric constant among other properties of note. Thus, an understanding of how such defects predictably modify the material properties of STO is advantageous in the implementation and rational tailoring of STO for use as a gas sensor. Herein, we present our approach to elucidate the relationship between the introduction of lanthanum (La) and magnesium (Mg) into bulk STO, respectively, as well as the emergence of oxygen vacancies in such structures and resulting structural, electronic, and optical properties. Specifically, we employed density functional theory (DFT) with GGA + U calculations to predict the energetic preferability of defect formation in STO bulk structures; the corresponding electronic properties—density of states (DOS) and band structures—and optical properties of energetically preferred geometries were calculated. Further, hydrogen and oxygen molecules were introduced to La-doped STO and Mg-doped STO bulk systems, respectively, to probe the probable adsorption sites of the species and identify the internal diffusion pathways that are critical to the gas sensing performance of doped bulk STO structures. Our results indicate that the tunability of the electronic and optical properties of STO is a feasible strategy to tailor STO-based materials for sensitive and highly selective gas sensing applications.