Strong modulation of optical properties in black phosphorus through strain-engineered rippling

TL;DR

This paper demonstrates that applying periodic strain to multilayer black phosphorus can significantly alter its optical properties, enabling tunable optoelectronic applications with large bandgap shifts.

Contribution

The study introduces a method of strain engineering in black phosphorus to achieve large optical property modulation, surpassing previous materials like transition metal dichalcogenides.

Findings

Optical absorption band-edge shifts by ~0.7 eV under strain.

Periodic stress can induce quantum confinement effects.

Large local charge carrier density variations are achievable.

Abstract

Controlling the bandgap through local-strain engineering is an exciting avenue for tailoring optoelectronic materials. Two-dimensional crystals are particularly suited for this purpose because they can withstand unprecedented non-homogeneous deformations before rupture: one can literally bend them and fold them up almost like a piece of paper. Here, we study multi-layer black phosphorus sheets subjected to periodic stress to modulate their optoelectronic properties. We find a remarkable shift of the optical absorption band-edge of up to ~0.7 eV between the regions under tensile and compressive stress, greatly exceeding the strain tunability reported for transition metal dichalcogenides. This observation is supported by theoretical models which also predict that this periodic stress modulation can yield to quantum confinement of carriers at low temperatures. The possibility of generating large strain-induced variations in the local density of charge carriers opens the door for a variety of applications including photovoltaics, quantum optics and two-dimensional optoelectronic devices.