Optical Properties and Band Structure of Boron Nitride Langmuir Films

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.

1. Shantanu Saha, A. Rice, Amob Ghosh, eds. Comprehensive characterization and analysis of hexagonal boron nitride on sapphire. AIP Advances, 2021, vol. 11, no. 5, pp. 055008. https://doi.org/10.1021/acs.cgd.2c00880

2. Gaokai Wang, Junhua Meng, Jingren Chen, eds. Epitaxy of hexagonal boron nitride thin films on sapphire for optoelectronics. Crystal Growth & Design, 2022, vol. 22, no. 12, pp. 7207–7214. https://doi.org/ 10.1021/acs.cgd.2c00880

3. Wigger D., Schmidt R., Del Pozo-Zamudo O., eds. Phonon-assisted emission and absorption of individual color centers in hexagonal boron nitride. 2D Materials, 2019, vol. 6, no. 3, pp. 035006. https://doi.org/10.1088/2053-1583/ab1188

4. Xiaofang Zhang, Lulu An, Changning Bai, eds. Hexagonal boron nitride quantum dots: Properties, preparation and applications. Materials Today Chemistry, 2021, vol. 20, pp. 100425. https://doi.org/10.1016/j.mtchem.2021.100425

5. Artús L., Feneberg M., Attaccalite C., eds. Ellipsometry study of hexagonal boron nitride using synchrotron radiation: transparency window in the Far‐UVC. Advanced Photonics Research, 2021, vol. 2, no. 5, pp. 2000101. https://doi.org/10.1002/adpr.202000101

6. Gaokai Wang, Jingren Chen, Junhua Meng, eds. Direct growth of hexagonal boron nitride films on dielectric sapphire substrates by pulsed laser deposition for optoelectronic applications. Fundamental Research, 2021, vol. 1, no. 6, pp. 677–683. https://doi.org/10.1016/j.fmre.2021.09.014

7. Xi Chen, Chunbo Tan, Xiaohang Liu, eds. Growth of hexagonal boron nitride films on silicon substrates by low-pressure chemical vapor deposition. Journal of Materials Science: Materials in Electronics, vol. 32, pp. 3713–3719. https://doi.org/10.1007/s10854-020-05116-6

8. Karim M., Lopes J. M., Ramsteiner M. The impact of ultraviolet laser excitation during Raman spectroscopy of hexagonal boron nitride thin films. Journal of Raman Spectroscopy, 2020, vol. 51, no. 12. pp. 2468–2477. https://doi.org/10.1002/jrs.6007

9. Singhal R., Echeverria E., Mcilroy D. N., eds. Synthesis of hexagonal boron nitride films on silicon and sapphire substrates by low-pressure chemical vapor deposition. Thin Solid Films, 2021, vol. 733, pp.138812. https://doi.org/10.1016/j.tsf.2021.138812

10. Seung Hee Lee, Hokyeong Jeong, Odongo Francis Ngome Okello, eds. Improvements in structural and optical properties of wafer-scale hexagonal boron nitride film by post-growth annealing. Scientific reports, 2019, vol. 9, no. 1, pp. 10590. https://doi.org/10.1038/s41598-019-47093-9

11. Seokmo Hong, Chang Seok Lee, Min-Hyun Lee, eds. Ultralow-dielectric-constant amorphous boron nitride. Nature, 2020, vol. 582, no. 7813, pp. 511–514. https://doi.org/10.1038/s41586-020-2375-9

12. Yeohghoon Jin, Yoonhyuk Rah, Junghoon Park, eds. Rapid and broad-range thickness estimation method of hexagonal boron nitride using Raman spectroscopy and optical microscope. Applied Physics Letters, 2020, vol. 116, no. 8, pp. 081104. https://doi.org/10.1063/1.5143972

13. Vijayesh Kumar, Kumar Nikhil, Partha Roy, eds. Emergence of fluorescence in boron nitride nanoflakes and its application in bioimaging. RSC advances, 2016, vol. 6, no. 53, pp. 48025–48032. https://doi.org/10.1016/j.rser.2022.112910

14. Qiuhong Yao, Yufeng Feng, Rong Mingcong, eds. Determination of nickel (II) via quenching of the fluorescence of boron nitride quantum dots. Microchimica Acta, 2017, vol. 184, pp. 4217–4223. https://doi.org/10.1016/j.mtchem.2021.100425

15. Bingping Liu, Shihai Yan, Zhongqian Song, Mengli Liu. One‐step synthesis of boron nitride quantum dots: Simple chemistry meets delicate nanotechnology. Chemistry–A European Journal, 2016, vol. 22. no. 52, pp. 18899–18907. https://doi.org/10.1016/j.mtchem.2021.100425

16. Li Chen, Xiaofang Zhang, Zhao Zhao, eds. Controllable preparation of boron nitride quantum dots with small size and strong blue photoluminescence. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2021, vol. 614, pp. 126181. https://doi.org/10.1016/j.mtchem.2021.100425

17. Nikolay N., Mendelson N., Özelci E., eds. Direct measurement of quantum efficiency of singlephoton emitters in hexagonal boron nitride. Optica, 2019, vol. 6, no. 8, pp. 1084–1088. https://doi.org/10.1088/1361-6633/ab6310

18. Seong-Yeon Lee, Tae-Young Jeong, Suyong Jung, eds. Refractive index dispersion of hexagonal boron nitride in the visible and near‐infrared. Physica status solidi (b), 2019, vol. 256, no. 6, pp. 1800417. https://doi.org/10.1002/pssb.201800417

19. Shayan Angizi, Sayed Ali Ahmad Alem, Mahdi Hasanzadeh Azar, eds. A comprehensive review on planar boron nitride nanomaterials: From 2D nanosheets towards 0D quantum dots. Progress in Materials Science, 2022, vol. 124, pp. 100884. https://doi.org/10.1016/j.pmatsci.2021.100884

20. Gil B., Cassabois G., Cusco R., eds. Boron nitride for excitonics, nano photonics, and quantum technologies. Nanophotonics, 2020, vol. 9, no. 11, pp. 3483–3504. https://doi.org/10.1515/nanoph-2020-0225