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 In2O3, thus forming an InSe/In2O3 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-In2O3 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.
Highlights
Stacking different two-dimensional (2D) van der Waals crystals to form heterostructures is a new route to the fabrication of electronic devices [1,2,3]
The oxidation can be activated in selected areas of the flake by a focused laser beam or prevented by capping the InSe surface with a film of hexagonal boron nitride (hBN)
Our data and analysis demonstrate that InSe nanolayers can be chemically stable under ambient conditions for several days
Summary
Stacking different two-dimensional (2D) van der Waals (vdW) crystals to form heterostructures is a new route to the fabrication of electronic devices [1,2,3]. Due to the numerous materials in the family of 2D vdW crystals, such as graphene, hexagonal boron nitride (hBN), metal dichalcogenides (MoS2, MoSe2, WS2, etc), IIIVI semiconductors (InSe, In2Se3, GaSe, GaTe, etc), and elemental semiconductors (black phosphorus, bP), a large and diverse variety of heterostructures are possible. This has already led to the successful fabrication of photodetectors, light emitting diodes, and high mobility field effect transistors [1, 2, 4,5,6,7,8,9,10,11,12,13]. The formation and control of such oxides in 2D flakes has not yet been examined and can offer opportunities to fabricate novel 2D hybrid heterostructures
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