Pressure‐Tuneable Visible‐Range Band Gap in the Ionic Spinel Tin Nitride

Abstract

The application of pressure allows systematic tuning of the charge density of a material cleanly, that is, without changes to the chemical composition via dopants, and exploratory high‐pressure experiments can inform the design of bulk syntheses of materials that benefit from their properties under compression. The electronic and structural response of semiconducting tin nitride Sn3N4 under compression is now reported. A continuous opening of the optical band gap was observed from 1.3 eV to 3.0 eV over a range of 100 GPa, a 540 nm blue‐shift spanning the entire visible spectrum. The pressure‐mediated band gap opening is general to this material across numerous high‐density polymorphs, implicating the predominant ionic bonding in the material as the cause. The rate of decompression to ambient conditions permits access to recoverable metastable states with varying band gaps energies, opening the possibility of pressure‐tuneable electronic properties for future applications.

Towards bipolar tin monoxide: Revealing unexplored dopants

“…Ample experimental studies of nano-and polycrystalline tin monoxide report transparency of 70% or greater in the visible range [14]. Optical properties can also be enhanced further via applied stress/strain or through external doping [46][47][48]. As such, the preservation of transparency may also be a relevant criteria when selecting dopants for SnO targeted towards specific applications.…”

A Novel High‐Pressure Tin Oxynitride Sn2N2O

“…predicted CaTi 2 O 4 ‐ and CaFe 2 O 4 ‐type orthorhombic structures at 40 and 60 GPa, respectively. On the other hand, Kearney et al . predicted structures with space groups P 2 1 / c and R c at pressures above 40 and 87 GPa, respectively.…”

“…Sn 3 N 4 adoptst he spinel structure at ambient pressurea nd transforms into post-spinel phases only above 40 GPa. Huang et al [23] predicted CaTi 2 O 4 -a nd CaFe 2 O 4 -type orthorhombic structuresa t4 0a nd 60 GPa, respectively.O nt he other hand, Kearney et al [24] predicted structures with space groups P2 1 /c and R3 c at pressures above 40 and 87 GPa, respectively.A ta mbient pressure,t he enthalpy of formation DH f of Pbcn-Sn 2 N 2 Of rom the binaries is + 0.56 eV/Sn 2 N 2 O; taking the more favourable (at zero pressure)d efect-spinel-typeo f Sn 2 N 2 Ot he enthalpy differencei ss till + 0.30 eV/Sn 2 N 2 O. This indicates that Sn 2 N 2 Oi smeta-stable with respectt od ecomposition into the binaries.…”

New nitrides: from high pressure–high temperature synthesis to layered nanomaterials and energy applications

“…Synchrotron X-ray emission and absorption (XES/XAS) studies were combined with ab initio theoretical calculations to understand the ground and excited state electronic structures and evaluation of the bandgap properties [44,45]. Recent laboratory investigations of the optical properties of Sn 3 N 4 are now revealing pressure-induced tuning of the bandgap between 1.3 and 3.0 eV under compression up to 100 GPa, leading to the possibility for controlling the optoelectronic properties via strain engineering [47]. Attention later focused on mixed-anion oxynitride spinels in the Si-Al-O-N and Ga-O-N systems [48][49][50][51], using synchrotron XAS to characterize the local structure around the Al 3+ cations [52].…”