Enhancing Infrared Light–Matter Interaction for Deterministic and Tunable Nanomachining of Hexagonal Boron Nitride

Abstract

Tailoring two-dimensional (2D) materials functionalities is closely intertwined with defect engineering. Conventional methods do not offer the necessary control to locally introduce and study defects in 2D materials, especially in non-vacuum environments. Here, an infrared pulsed laser focused under the metallic tip of an atomic force microscope cantilever is used to create nanoscale defects in hexagonal boron nitride (h-BN) and to subsequently investigate the induced lattice distortions by means of nanoscale infrared (nano-IR) spectroscopy. The effects of incoming light power, exposure time, and environmental conditions on the defected regions are considered. Nano-IR spectra complement the morphology maps by revealing changes in lattice vibrations that distinguish the defects formed under various environments. This work introduces versatile experimental avenues to trigger and probe local reactions that functionalize 2D materials through defect creation with a higher level of precision for applications in sensing, catalysis, optoelectronics, quantum computing, and beyond.

Locally strained hexagonal boron nitride nanosheets quantified by nanoscale infrared spectroscopy

“…33 Hence, the rapid heating caused by the laser pulse combined with the lighting-rod effect due to the Au nanoIR tip engenders deformation of the basal plane of h-BN that results in a plastic distortion. The effect has been demonstrated on several substrates, 33 suggesting that it originates from the local response of h-BN in contact with the Au tip. Additional evaluation of the experimental conditions indicates that the most noticeable distortions result from an illumination wavenumber corresponding to the E 1u phonon mode.…”

“…Additional evaluation of the experimental conditions indicates that the most noticeable distortions result from an illumination wavenumber corresponding to the E 1u phonon mode. 33…”

“…Nonetheless the formation of the nanobump when using the Au tip suggests a beneficial participation of the metallic tip to engineer local strain in h-BN. 33 Hence, the rapid heating caused by the laser pulse combined with the lighting-rod effect due to the Au nanoIR tip engenders deformation of the basal plane of h-BN that results in a plastic distortion. The effect has been demonstrated on several substrates, 33 suggesting that it originates from the local response of h-BN in contact with the Au tip.…”

“…Additional evaluation of the experimental conditions indicates that the most noticeable distortions result from an illumination wavenumber corresponding to the E 1u phonon mode. 33 NanoIR spectra were collected by monitoring the amplitude of the first contact resonance of the cantilever as a function of the wavenumber emitted by the optical parametric oscillator (OPO), from 1000 to 1800 cm −1 (see details in the Methods section). The laser power used for nanoIR spectra collection was maintained below 0.6 mW under nitrogen to prevent permanent deformation of the lattice.…”

Room temperature 3D carbon microprinting

“…This perspective is further exciting if thought of in combination with defects engineering prospects for nanopatterning of reactive sites. In this respect, recent light-assisted local defects nanomachining in 2D materials 37 indicates that scalable manufacturing of reactive sites separated by nanoscale pitches and structured surfaces is within reach. These innovative micro-and nanoprinting methods provide an eco-friendlier impetus to impact the next-generation of carbon materials for applications in flexible electronics, quantum information, sensing, catalysis, and beyond.…”