Anisotropic Optical Properties of Hexagonal Boron Nitride Thin Films

TL;DR

This study investigates the anisotropic optical properties of thin films made from ultrasonically prepared hexagonal boron nitride flakes, revealing hidden anisotropy through spectral polarization analysis and statistical microscopy.

Contribution

It introduces a method to detect macroscopic anisotropy in BN thin films that is not explained by individual particle orientation.

Findings

Revealed hidden optical anisotropy in BN thin films

Linked polarization anisotropy to particle density distribution

Demonstrated macroscopic ordering correlates with optical axis

Abstract

Few-layer flakes of hexagonal boron nitride were prepared by ultrasonication of bulk crystals and agglomerated to form thin films. The transmission and reflection spectra of the thin films were measured. The spectral dependences of the linear and circular polarization revealed a hidden anisotropy of the films over the whole sample area which could not be explained by the anisotropy of the chaotically-oriented individual particles. Statistical analysis of optical microscopy images showed a macroscopic particle density distribution with ordering corresponding to the optical axis observed in the polarization data.