Influence of crystal structure on charge carrier effective masses in BiFeO3

Abstract

Ferroelectric-based photovoltaics have shown great promise as a source of renewable energy, thanks to their in-built charge separation capability, yet their efficiency is often limited by low charge carrier mobilities. In this work, we compare the photovoltaic prospects of various phases of the multiferroic material BiFeO 3 by evaluating their charge carrier effective masses from first-principles simulations. We identify a tetragonal phase with the promising combination of a large spontaneous polarisation and relatively light charge carriers. From a systematic investigation of the octahedral distortions present in BiFeO 3 , we clarify the relationship between structure and effective masses. This relationship is explained in terms of changes to the orbital character and overlap at the band edges that result from changes in the geometry. Our findings suggest some design principles for how to tune effective masses in BiFeO 3 and similar materials through the manipulation of their crystal structures in experimentally accessible ways. arXiv:1804.02898v2 [cond-mat.mtrl-sci]

Metastable Tetragonal BiFeO3 Stabilized on Anisotropic a-Plane ZnO

“…9,10 Moreover, it was reported very recently that T-BFO has a rather low effective electron mass that is comparable with those of high-mobility oxides such as Ga 2 O 3 and BaSnO 3 . 11 Based on these facts, T-BFO has been emerging as a promising candidate for oxide electronics and spintronics.…”

“…Although anisotropic strain is powerful in tuning charge and spin phases, 21,22 it was seldom utilized to manipulate the structural phase transitions due to the limited anisotropies of the commonly used substrates. Herein, a strongly anisotropic template−nonpolar (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)-faceted ZnO (abbreviated as a-ZnO) was employed to exert highly anisotropic strains on BFO. The hexagonal ZnO unit cell corresponds to an orthogonal one through index transformation, 23 with ZnO (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) as one of the basal planes.…”

“…Herein, a strongly anisotropic template−nonpolar (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)-faceted ZnO (abbreviated as a-ZnO) was employed to exert highly anisotropic strains on BFO. The hexagonal ZnO unit cell corresponds to an orthogonal one through index transformation, 23 with ZnO (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) as one of the basal planes. Large compressive and tensile strains are respectively imposed along two orthogonal ⟨110⟩ directions of BFO, shifting the energy balance between competing phases.…”

“…As a consequence, T-BFO with a critical thickness of 110 nm can be stabilized on a-ZnO at room temperature. (10)(11)(12) substrates. For the ZnO growth, a commercial ZnO ceramic target was employed.…”

Antiperovskite Oxides as Promising Candidates for High-Performance Ferroelectric Photovoltaics: First-Principles Investigation on Ba4As2O and Ba4Sb2O

“…Band gap energy and effective mass of various ferroelectric semiconductors. Red squares denote the data for Ba 4 Pn 2 O, blue squares for synthesized materials (β-CuGaO 2 , , BiFeO 3 , , KNbO 3 , , BaTiO 3 , , ZnSnO 3 , Sn 2 P 2 Se 6 , and Sn 2 P 2 S 6 ), and purple circles for theoretically suggested materials [ZnSnS 3 and ABiO 3 (A = Cd, Zn, Ca, and Mg) . The vertical dashed line indicates the Shockley–Queisser value of the band gap.…”