Full Crystallographic Imaging of Hexagonal Boron Nitride Monolayers with Phonon-Enhanced Sum-Frequency Microscopy.

ABSTRACT: Hexagonal boron nitride (hBN) is an important 2D material for van der Waals heterostructures, single photon emitters, and infrared nanophotonics. The optical characterization of mono- and few-layer samples of hBN however, remains a challenge as the material is almost invisible optically. Here, phase-resolved sum-frequency microscopy is introduced as a technique for imaging monolayers of hBN grown by chemical vapor deposition (CVD) and visualizing their crystal orientation. Femtosecond mid-infrared (IR) and visible laser pulses are used for sum-frequency generation (SFG), which is imaged in a wide-field optical microscope. The IR laser resonantly excites a phonon of hBN that leads to an ≈800-fold enhancement of the SFG intensity, making it possible to image large 100 × 100 µm² sa

SUBMITTER: Mueller NS 

PROVIDER: S-EPMC12862746 | biostudies-literature | 2026 Feb

REPOSITORIES: biostudies-literature