Optical Properties and Band Structure of Boron Nitride Langmuir Films

Abstract

Purpose. Investigate the structural features of boron nitride films obtained by the Langmuir-Blodgett method. Observe fluorescence spectra and determine the band structure of the resulting coatings using optical methods.Methods. The deposition of Langmuir films was carried out using the KSV NIMA 2002 setup from the colloidal solution of ST BN/CHCl3. The study of optical properties was conducted using the SF 2000 spectrophotometer in spectral range 200 – 1100 nm and the confocal Raman microspectrometer OmegaScope AIST-NT with spectral resolution 3 cm-1. Surface morphology investigation was performed using the scanning probe microscope SmartSPM AIST-NT with standard silicon cantilevers NSA10, tip radius 7 nm. The band structure modeling of stabilized boron nitride nanoparticles was carried out using the MaterialsStudio 2020 software package with the CASTEP module.Results. The spectral characteristics of deposited film structures made of stabilized hexagonal boron nitride nanoparticles have been investigated. The hydrodynamic size of the nanoparticles was determined to be ~100 nm using optical methods, while the lateral size of the nanoparticles in Langmuir films was found to be 84.6 nm, calculated from the spectral peak at 1360 cm-1 with E2g symmetry, and 82.4 nm based on scanning probe microscopy data. Absorption and fluorescence spectra of colloidal particles were obtained, showing an unusually large Stokes shift of 105 nm and a quantum yield of 0.72. The bandgap width of the stabilized nanoparticles was measured using the Tautz method and ab-initio modeling, resulting in values of 5.79 eV and 5.46 eV, respectively. Conclusion. The study examines the surface morphology, optical properties, and band structure of the deposited Langmuir films made of stabilized boron nitride nanoparticles.