Band gap bowing in NixMg1−xO

Abstract

Epitaxial transparent oxide NixMg1−xO (0 ≤ x ≤ 1) thin films were grown on MgO(100) substrates by pulsed laser deposition. High-resolution synchrotron X-ray diffraction and high-resolution transmission electron microscopy analysis indicate that the thin films are compositionally and structurally homogeneous, forming a completely miscible solid solution. Nevertheless, the composition dependence of the NixMg1−xO optical band gap shows a strong non-parabolic bowing with a discontinuity at dilute NiO concentrations of x < 0.037. Density functional calculations of the NixMg1−xO band structure and the density of states demonstrate that deep Ni 3d levels are introduced into the MgO band gap, which significantly reduce the fundamental gap as confirmed by optical absorption spectra. These states broaden into a Ni 3d-derived conduction band for x > 0.074 and account for the anomalously large band gap narrowing in the NixMg1−xO solid solution system.

Epitaxial Growth and Bandgap Control of Ni1−xMgxO Thin Film Grown by Mist Chemical Vapor Deposition Method

“…The bandgaps of Ni1-xMgxO thin films in previous reports grown by the various methods [4,6,[14][15][16] are also shown for comparison. The bandgaps observed herein have the same tendency as those of previous studies [17]: the bandgap increases with increasing Mg composition. The bandgap reached 3.9 eV with a Ni1-xMgxO thin film with x = 0.28.…”

Polarization‐Modulated Photovoltaic Effect at the Morphotropic Phase Boundary in Ferroelectric Ceramics

“…As the BNT concentration increases, the Ni 3d states further broaden to form the conduction band minimum, leading to a stable gap which is not strongly dependent on the composition. [24] FE hysteresis loops of these two compositions were measured using a Ag/FE pellet (0.5 mm)/Ag configuration at 1 Hz. The polarization charge and switching current are plotted as a function of applied electric field in Figure 1e,f.…”

Bandgap bowing in a zero-dimensional hybrid halide perovskite derivative: spin–orbit coupling versus lattice strain

“…Since, in general, bandgap of a semiconductor alloy under the effect of bowing is smaller than the value estimated from the linear interpolation between the bandgaps of the end members; the bowing coefficient b is a positive quantity. 21 Typically, if b is small (a fraction of an electronvolt) and independent of composition, the bowing in most cases can be explained by the structural disorder effect. 22 solid solution, the variation in the bandgap with metal-composition cannot be explained by a single bowing coefficient.…”

“…It is apparent that the hexagonal symmetry of MA 16,21,23 Unlike the inorganic alloys, the underline mechanism of bandgap bowing in hybrid perovskite alloys is not clearly known yet and has been proposed so far as a competing effect between spin-orbit coupling (SOC) and lattice distortion. 16 As such, in the absence of a SOC effect, the optical bandgap of an alloy increases upon addition of an element having a higher effective ionic radius and the increase is expected to be linear following Vegard's law.…”