Electronic structure of bulk and two-dimensional SrTiO 3 : DFT calculation with GGA + U methods
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RESEARCH PAPER
Electronic structure of bulk and two-dimensional SrTiO3: DFT calculation with GGA + U methods Aqing Chen & Selvakumar V. Nair & Bojan Miljkovic & Christina Souza & Harry E. Ruda & Zhenguo Ji
Received: 9 February 2020 / Accepted: 18 August 2020 # Springer Nature B.V. 2020
Abstract Electron structure of bulk and twodimensional SrTiO3 (2D-SrTiO3) were calculated using the first-principle approach based on the density functional theory (DFT) with GGA + U methods. An accurate direct band gap of bulk SrTiO3 of 3.52 eV and indirect band gap of 3.06 eV were obtained with the optimum UTi-3d = 6.0 eV and USr-3d = 3.0 eV. It is found that the electronic structure of 2D-SrTiO3 is strongly affected by the surface atoms. Most interestingly, the band gap of 2D-SrTiO3 is much smaller than that of the bulk material and is nearly independent of thickness. The origin of this behavior is traced to the nature of the conduction band in 2D-SrTiO3.
Keywords Two dimensional SrTiO3 . Band structures . DFT calculations
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11051-020-04994-5) contains supplementary material, which is available to authorized users. A. Chen (*) : Z. Ji College of Materials & Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018, People’s Republic of China e-mail: aqchen@hdu.edu.cn S. V. Nair : B. Miljkovic : C. Souza : H. E. Ruda Centre for Advanced Nanotechnology, University of Toronto, Toronto, Ontario M5S3E3, Canada
Introduction SrTiO3, the best known and most widely perovskite materials for oxide electronics (Ramirez 2007), has been widely used in metal-insulator transitions (Cen et al. 2008; Noller et al. 2006), superconductivity (Cossio et al. 2012) or large negative magnetoresistance (Brinkman et al. 2007), as well as photocatalysts (Can and Yildirim 2018; Li et al. 2018; Shenoy et al. 2018). Ultrathin single-crystalline two-dimensional transitionmetal oxide perovskites are expected to have novel properties with potential to be used in multifunctional electronic devices due to the strongly interacting electrons of the d orbital that give rise to a rich spectrum of exotic phases (Ji et al. 2019). Since the physical nature of the electronic structure and the chemical character of the subbands (Cen et al. 2008; Raghavan et al. 2013; Santander-Syro et al. 2011) is crucial to understand properties of such materials, numerous investigations on the electronic band structure have been done both experimentally and theoretically. In fact, two-dimensional film of SrTiO3 (2D-SrTiO3) has been fabricated successfully (Ji et al. 2019) in the year 2019. It also provides great opportunities for studying the correlated phases and interfacial phenomena of two-dimensional transition-metal oxide perovskites. However, the electronic band structure of ultrathin single-crystalline 2D-SrTiO3 as thin as a few atomic layers is still unclear and there is no recent reasonable theoretical works on it. Although the density functional theory (DFT) can effecti
