Correlation of size and oxygen bonding at the interface of Si nanocrystal in Si–SiO2 nanocomposite: A Raman mapping study. (26th October 2015)

• Record Type: Journal Article
• Authors: Rani, Ekta; Ingale, Alka A.; Chaturvedi, A.; Kamal, C.; Phase, D. M.; Joshi, M. P.; Chakrabarti, A.; Banerjee, A.; Kukreja, L. M.
• Is Part Of: Journal of Raman spectroscopy. Volume 47:Number 4(2016)
• Page Start: 457
• Page End: 467
• Publication Date: 2015-10-26
• Subjects: Raman spectroscopy/mapping -- Si nanocrystals -- nanocomposite -- Si–SiO2 interface -- DFT/TDDFT calculations; Raman spectroscopy -- Periodicals; 535.846
• DOI: 10.1002/jrs.4832
• Languages: English
• ISSNs: 0377-0486

Abstract

Abstract : Raman spectroscopy/mapping is used to investigate the variation of Si phonon wavenumbers, i.e., lower wavenumber (LW ~ 495–510 cm −1 ) and higher wavenumber (HW ~ 515–519 cm −1 ) phonons, observed in Si–SiO2 multilayer nanocomposite (NCp) grown using pulsed laser deposition. Sensitivity of Raman spectroscopy as a local probe to surface/interface is effectively used to show that LW and HW phonons originate at surface (Si–SiO2 interface) and core of Si nanocrystals, respectively. The consistent picture of this understanding is developed using Raman spectroscopy monitored laser heating/annealing and cooling experiment at the site of the desired wavenumber, chosen with the help of Raman mapping. Raman spectra calculations for Si41 cluster with oxygen and hydrogen termination show strong mode at 512 cm −1 for oxygen terminated cluster corresponding to the vibration of surface Si atoms. This supports our attribution of LW phonons to be originating at the Si–SiO2 surface/interface. These results along with XPS show that nature of interface (oxygen bonding) in turn depends on the size of nanocrystals and LW phonons originate at the surface of smaller Si nanocrystals. The understanding developed can conclude the ongoing debate on large variation in Si phonon wavenumbers of Si–SiO2 NCps in the literature. Copyright © 2015 John Wiley & Sons, Ltd. Abstract : Raman spectroscopy monitored laser heating and cooling experiment in corroboration with density functional theory /time‐dependent density functional theory calculations, and X‐ray photoelectron spectroscopy suggests the following: Si phonons in the range 495–510 cm ‐1 (Lorentzian line shape) originate from the smaller size Si nanocrystals, and its wavenumber is governed by dominant surface/interface effect. Si phonons in the range 515–519 cm ‐1 (asymmetric line shape) originate from larger size Si nanocrystals, where core phonon is dominant, and its wavenumber is governed by the confinement effect.