Enhanced Optical Emission from 2D InSe Bent onto Si‐Pillars

Abstract

Controlling the propagation and intensity of an optical signal is central to several technologies ranging from quantum communication to signal processing. These require a versatile class of functional materials with tailored electronic and optical properties, and compatibility with different platforms for electronics and optoelectronics. Here, the inherent optical anisotropy and mechanical flexibility of atomically thin semiconducting layers are investigated and exploited to induce a controlled enhancement of optical signals. This enhancement is achieved by straining and bending layers of the van der Waals crystal indium selenide (InSe) onto a periodic array of Si‐pillars. This enhancement has strong dependence on the layer thickness and is modelled by first‐principles electronic band structure theory, revealing the role of the symmetry of the atomic orbitals and light polarization dipole selection rules on the optical properties of the bent layers. The effects described in this paper are qualitatively different from those reported in other materials, such as transition metal dichalcogenides, and do not arise from a photonic cavity effect, as demonstrated before for other semiconductors. The findings on InSe offer a route to flexible nano‐photonics compatible with silicon electronics by exploiting the flexibility and anisotropic and wide spectral optical response of a 2D layered material.

Engineering the Dipole Orientation and Symmetry Breaking with Mixed‐Dimensional Heterostructures

“…Our EF is the highest among the results using the topographical changes, and is comparable to the mechanical strain method. Further, in contrast to the previously demonstrated methods (e.g., strain, [ 31 ] nanoparticles, [ 32 ] nanopillar arrays, [ 33 ] and wrinkles [ 34 ] ), our demonstrated robust method offers better uniformity, deterministic positioning and controllability, less fabrication complexity, and larger anisotropic response.…”

“…Three distinctive Raman modes of InSe are observed in the range of 100-300 cm −1 : A 1 (Γ) at ≈115 cm −1 , E(Γ) at ≈176 cm −1 , and A 1 (Γ) at ≈227 cm −1 , being in good agreement with previous reports. [31,33] The origin of the three Raman modes is depicted in the inset. The peak at ≈260 cm −1 belongs to the AlGaAs NW.…”

“…[28][29][30] Therefore, unlike typical TMDCs with in-plane (IP) dipole, the band edge transitions of InSe cannot couple effectively to light at a normal incident angle, largely hindering the InSe-based potential optoelectronic applications. Different approaches have been demonstrated to engineer the dipole orientation of InSe and enhance the light-matter interactions, for example, by applying strain, [31] nanotexturing with SiO 2 nanoparticles, [32] bending the flake onto an array of Si-nanopillars, [33] and forming localized wrinkles. [34] In this work, we report a new approach to engineer the dipole orientation of InSe by integrating 2D InSe with 1D AlGaAs nanowire (NW).…”

Strain-tuning of the electronic, optical, and vibrational properties of two-dimensional crystals

“…Single or multiple layers can indeed conform to the shape of the patterned substrate underneath, resulting in a localized layer deformation. [25][26][27][28][29][30][31][32][33] This method was used by several groups to create restricted regions of a TMD crystal subjected to strain fields, as depicted in Fig. 1.…”

Fabrication Methods for Integrating 2D Materials

“…Strain engineering has been another effective way to tune the properties of 2D materials, [424,[438][439][440] although it is relatively slow compared to the gate or optical tuning. The ability to apply continuous and reversible strain to 2D layers is highly useful for dynamically tuning their properties.…”