Quantum-chemical perspective of nanoscale Raman spectroscopy with the three-dimensional phonon confinement model

Abstract

Raman spectroscopy of crystalline/molecular systems is well grounded with quantum-chemical calculations and group theory, making it a unique tool for material characterization. For the intermediate' case of nanometer-scale systems, however, the application of Raman spectroscopy is limited by the lack of such theoretical bases. Here, we couple a scaled quantum-chemical calculation with the phonon confinement model to construct a universal and physically consistent basis for nanoscale Raman spectroscopy. Unlike the commonly assumed one-dimensional approximation of phonon dispersion, we take into account the confinement along all the three dimensions of the k-space. We apply it to diamond nanoparticles of sub-50-nm size, a system with pronounced anisotropy of dispersion for which consideration of three-dimensional dispersion is a requisite. The model excellently reproduces size-sensitive Raman spectral features, including the peak position, bandwidth, and asymmetry of the sp(3) C-C stretch Raman line. This fundamental approach can be easily generalized to contribute the future development of quantitative nanoscale Raman spectroscopy. Copyright (c) 2017 John Wiley & Sons, Ltd.