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

Abstract

Exploitation of two-dimensional (2D) van der Waals (vdW) crystals can be hindered by the deterioration of the crystal surface over time due to oxidation. On the other hand, the existence of a stable oxide at room temperature can offer prospects for several applications. Here we report on the chemical reactivity of γ-InSe, a recent addition to the family of 2D vdW crystals. We demonstrate that, unlike other 2D materials, InSe nanolayers can be chemically stable under ambient conditions. However, both thermal-and photo-annealing in air induces the oxidation of the InSe surface, which converts a few surface layers of InSe into In 2 O 3 , thus forming an InSe/In 2 O 3 heterostructure with distinct and interesting electronic properties. The oxidation can be activated in selected areas of the flake by laser writing or prevented by capping the InSe surface with an exfoliated flake of hexagonal boron nitride. We exploit the controlled oxidation of p-InSe to fabricate p-InSe/n-In 2 O 3 junction diodes with room temperature electroluminescence and spectral response from the near-infrared to the visible and near-ultraviolet ranges. These findings reveal the limits and potential of thermal-and photo-oxidation of InSe in future technologies.

Atomic-scale mechanisms of defect- and light-induced oxidation and degradation of InSe

“…. 32 It is expected that these defective states act as trapping and scattering centers for conducting carriers and decrease their electronic mobility.…”

Monolayer group-III monochalcogenides by oxygen functionalization: a promising class of two-dimensional topological insulators

“…Balakrishnan et al controllably oxidized the surface of InSe nanolayers by photo-annealing and thermal-annealing in air, and obtained InSe/In 2 O 3 heterostructures as p-n junctions with tunable band gap. 30 Beechem et al and Del Pozo-Zamudio et al showed that oxidation of ultrathin GaSe and InSe films lead to the reduction of photoluminescence. 31,32 However, the structures, physical, and chemical properties of the modified MX sheets are still unclear and await explorations.…”

Impedance and Photosensitivity Spectra of Nanocomposite Structures Based on Layered Semiconductor InSe and Ionic Salt RbNO3

“…Structurally perfect InSe crystals are characterized by higher values of electron mobility (>10 3 cm 2 V −1 s −1 at Т = 300 K) as compared to other 2D materials. They are also more resistant with respect to environment influence (molecules of H 2 O and O 2 ) . Various van der Waals heterostructures based on this material have high‐quality interfaces .…”

“…They are also more resistant with respect to environment influence (molecules of H 2 O and O 2 ) . Various van der Waals heterostructures based on this material have high‐quality interfaces . Intense researchеs of 2D materials resulted in the creation of a new class of structures that have “ionotronic” characteristics .…”