Spectroscopic size and thickness metrics for liquid-exfoliated h-BN

Aideen Griffin, Andrew Harvey, Brian Cunningham, Declan Scullion, Tian Tian, Chih-Jen Shih, Myrta Gruening, John F Donegan, Claudia Backes, Elton Santos, Jonathan N. Coleman

Research output: Contribution to journalArticlepeer-review

33 Citations (Scopus)
231 Downloads (Pure)

Abstract

For many 2D materials, optical and Raman spectra are richly structured, and convey information on a range of parameters including nanosheet size and defect content. By contrast, the equivalent spectra for h-BN are relatively simple, with both the absorption and Raman spectra consisting of a single feature each, disclosing relatively little information. Here, the ability to size-select liquid-exfoliated h-BN nanosheets has allowed us to comprehensively study the dependence of h-BN optical spectra on nanosheet dimensions. We find the optical extinction coefficient spectrum to vary systematically with nanosheet lateral size due to the presence of light scattering. Conversely, once light scattering has been decoupled to give the optical absorbance spectra, we find the size dependence to be mostly removed save for a weak but well-defined variation in energy of peak absorbance with nanosheet thickness. This finding is corroborated by theoretical calculations. In addition, while we find the position of the sole h-BN Raman line to be invariant with nanosheet dimensions, the linewidth appears to vary weakly with nanosheet thickness. These size-dependent spectroscopic properties can be used as metrics to estimate nanosheet thickness from spectroscopic data.
Original languageEnglish
Pages (from-to)1998-2005
Number of pages8
JournalChemistry of Materials
Volume30
Issue number6
Early online date01 Mar 2018
DOIs
Publication statusPublished - 2018

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