Nanotexturing To Enhance Photoluminescent Response of Atomically Thin Indium Selenide with Highly Tunable Band Gap

Abstract

Manipulating properties of matter at the nanoscale is the essence of nanotechnology, which has enabled the realization of quantum dots, nanotubes, metamaterials, and two-dimensional materials with tailored electronic and optical properties. Two-dimensional semiconductors have revealed promising perspectives in nanotechnology. However, the tunability of their physical properties is challenging for semiconductors studied until now. Here we show the ability of morphological manipulation strategies, such as nanotexturing or, at the limit, important surface roughness, to enhance light absorption and the luminescent response of atomically thin indium selenide nanosheets. Besides, quantum-size confinement effects make this two-dimensional semiconductor to exhibit one of the largest band gap tunability ranges observed in a two-dimensional semiconductor: from infrared, in bulk material, to visible wavelengths, at the single layer. These results are relevant for the design of new optoelectronic devices, including heterostructures of two-dimensional materials with optimized band gap functionalities and in-plane heterojunctions with minimal junction defect density.

Engineering p – n junctions and bandgap tuning of InSe nanolayers by controlled oxidation

“…Among these vdW crystals, γ-InSe, a direct-band gap semiconductor, is attracting increasing interest. Strong quantum confinement effects with decreasing layer thickness and high room temperature electron mobility (>0.1 m 2 V −1 s −1 ) have been achieved in exfoliated InSe and/or films grown by physical vapour deposition [14][15][16][17][18][19]. Although the chemical stability of InSe has been questioned [20], recent research has shown that 2D InSe can be chemically inert under ambient conditions [21].…”

The direct-to-indirect band gap crossover in two-dimensional van der Waals Indium Selenide crystals

“…InSe/hBN)13 and texturised (e.g. InSe/SiO 2 )18 layers. In the latter case, the surface of InSe flakes is bent by SiO 2 nanoparticles trapped between the flakes and the substrate, thus enhancing the optical emission due to increased light scattering and modified dipolar selection rules18.…”

Engineering light emission of two-dimensional materials in both the weak and strong coupling regimes

“…On the one hand, this issue is important for 2D semiconductors different from 2D TMDs [46]. In fact, the nature of the orbitals involved in the optical bandgap and the dipolar selection rules for optical transitions of 2D InSe -a semiconductor with a highly tunable band gap [35,51] -suggest that InSe could be an example of a 2D material with an important out-of-plane dipole contribution. On the other hand, the design of multilayer structures with optimized light extraction capabilities (independently of their dipole orientation) is also relevant for 2D TMDs, as it may allow to relax nearly flat requisites of devices based on these materials to provide an optimal response.…”

“…However, this model assumes normal incidence of light for both excitation and emission, which limits its applicability for the design of devices in which the angular light emission pattern or the power distribution into guided and leaky modes becomes a relevant parameter. In addition to this, the normal emission approximation would be expected to fail to account for light emission patterns of active 2D materials with vertical emitting dipoles (as would be the case for 2D materials such as InSe [35,36]). In order to overcome such issues, it is possible to use matrix-based analytical models under the assumption of dipolar nature of optical processes taking place in semiconductors.…”