Band gap tuning of epitaxial SrTiO3-δ/Si(001) thin films through strain engineering

Abstract

We investigate the effect of strain and oxygen vacancies (VO) on the crystal and optical properties of oxygen deficient, ultra-thin (4–30 nm) films of SrTiO3-δ (STO) grown heteroepitaxially on p-Si(001) substrates by molecular beam epitaxy. We demonstrate that STO band gap tuning can be achieved through strain engineering and show that the energy shift of the direct energy gap transition of SrTiO3-δ/Si films has a quantifiable dimensional and doping dependence that correlates well with the changes in crystal structure.

Prediction of orientation relationships and interface structures between α-, β-, γ-FeSi2 and Si phases

“…In that, prediction of possible coherent interfaces with regular atomic structure is of great importance due to the stability of their electronic and transport properties on the one hand, and the compatibility of such substrate and film phases for epitaxial growth on the other hand. Feasibility of high-quality thin film synthesis is of particular interest in lattice strain band engineering (Cottier et al, 2015;Seo et al, 2019) and for most of the applications in spintronics and optoelectronics. A vivid example of such a case is the epitaxial synthesis of -FeSi 2 on silicon substrates.…”

Optics of epitaxial strained strontium titanate films

“…[10][11][12][13][14][15][16] However, the experimentally observed optical properties of epitaxial films do not always agree with modeling and are scattered and often poorly understood. [2][3][4][5]17,18 Apart from unintentional technological issues, this disparity indicates insufficient knowledge of optical phenomena in epitaxial films and creates a bottleneck for potential applications. Here, we aim to better clarify these phenomena in epitaxial strained films of representative STO.…”

“…1(a)] show that the AFD film is highly transparent at the energies E < 3.5 eV, in contrast to substantial absorption for this spectral range in non-stoichiometric STO films. 18,25 The film's spectrum is clearly shifted to higher photon energies compared to that of the crystal, and the blueshift is accompanied by a relative suppression or smearing of the spectral features. This behavior indicates an uplift of the conduction band and changes of the interband transitions in the film.…”