Probing Anisotropic Deformation and Near-Infrared Emission Tuning in Thin-Layered InSe Crystal under High Pressure

Abstract

Indium selenide (InSe) exhibits high lattice compressibility and an extraordinary capability of tailoring the optical band gap under pressure beyond other 2D materials. Herein, by applying hydrostatic pressure via a diamond anvil cell, we revealed an anisotropic deformation dynamic and efficient manipulation of near-infrared light emission in thin-layered InSe strongly correlated to layer numbers (N = 5−30). As N > 20, the InSe lattice is compressed in all directions, and the intralayer compression leads to widening of the band gap, resulting in an emission blue shift (∼120 meV at 1.5 GPa). In contrast, as N ≤ 15, an efficient emission red shift is observed from band gap shrinkage (rate of 100 meV GPa −1 ), which is attributed to the predominant uniaxial interlayer compression because of the high strain resistance along the InSe−diamond interface. These findings advance the understanding of pressure-induced lattice deformation and optical transition evolution in InSe and could be applied to other 2D materials.

Giant Out-of-Plane Exciton Emission Enhancement in Two-Dimensional Indium Selenide via a Plasmonic Nanocavity

“…Nevertheless, the two-dimensional InSe, with OP excitonic features, demonstrates high exciton densities by suppressed electron–hole pair recombination. InSe provides a suitable platform for studying excitonic complexes and exciton condensation. − The intrinsic OP orientation of excitons in two-dimensional InSe arises from the behavior of electronic states under an inversion symmetry operation . The distinctive OP exciton transition is derived from the conduction band minimum (CBM), which is dominated by the antibonding s orbital of the In atom, and the valence band maximum (VBM), which is dominated by the nonbonding p z orbital of the Se atom .…”

Stacking Faults Enabled Second Harmonic Generation in Centrosymmetric van der Waals RhI3

“…DFT calculations were performed to simulate the evolution of the SHG response of RhI 3 under different pressures. Because vdW RhI 3 nanoflakes are primarily adsorbed on the surface of diamond anvil during high-pressure experiments, the external pressure is mainly out-of-plane and would result in obvious compression of interlayer spaces . Based on this phenomenon, 2L AC̅ RhI 3 with the interlayer distance decreased by 2.5% and 5% are used to simulate the system under low pressure (below 3 GPa) .…”

“…Because vdW RhI 3 nanoflakes are primarily adsorbed on the surface of diamond anvil during high-pressure experiments, the external pressure is mainly out-of-plane and would result in obvious compression of interlayer spaces. 45 Based on this phenomenon, 2L AC̅ RhI 3 with the interlayer distance decreased by 2.5% and 5% are used to simulate the system under low pressure (below 3 GPa). 46 SHG spectra with and without pressure corresponding to |χ yyy (2) |, |χ yxx (2) |, and |χ xxy (2) | with and without the compression of interlayer distance are shown in Figures 6a and S17, respectively.…”

Strong Linearly Polarized Light Emission by Coupling Out-of-Plane Exciton to Anisotropic Gap Plasmon Nanocavity

“…In contrast to group VI TMDs, InSe undergoes a crossover from indirect to direct band gap transition as the layer thickness increases . As a result, two-dimensional InSe flakes with a layer number above 7 all support direct exciton emission with out-of-plane dipole orientation as well as a thickness controllable emission wavelength, making it a promising candidate for developing nanophotonic and optoelectronic devices for on-chip applications. − However, compared to the TMD monolayer, the excitonic emission in InSe is still relatively weak. Thus, so far, there is still a lack of reports on the InSe-based light-emitting diode.…”