Application of Polarized Raman Spectroscopy in Precise Atomic Displacement Detection

ABSTRACT Raman spectroscopy basically probes the changes in polarizability induced by lattice vibration, popularly known as Raman tensor which is highly sensitive to the interatomic distances. The question is how precisely this can be probed. Can Raman spectroscopy sense very small atomic displacement, say femtometer displacement? The answer is yes; now, it is a reality, thanks to the light polarization dependence of the Raman scattering. In this review, we discuss the working principles of the atomic displacement detection protocol using angle resolved polarized Raman spectroscopy and theoretical formulation of the relation between the directional atomic displacement (strain) and spectral parameters along with some experimental results on different classes of materials like multiferroic and ferroelectric. The very high detection capability of this technique enables one to unearth the microscopic mechanism of the electric polarization in Type II multiferroic material CuO and resolve the long‐standing debate on crystal symmetry of the popularly used substrate material NdGaO 3 and detection of Ti displacement in classical ferroelectric BaTiO 3 . Remarkably, the required apparatus is very simple; it includes a polarization analysis capable Raman spectrometer to probe a specific Raman tensor element, a sample rotation stage to adjust the polarization of the incident and scattered light with respect to crystallographic orientations, and of course sample should be single crystals or epitaxial thin film. The simple instrumental requirements, straightforward direct method of atomic displacement detection, high sensitivity for the low atomic number elements, and microscopic special resolution make it highly useful in future applications where small atomic displacement (particularly from the center of symmetry) to external factors like temperature, pressure, and electric or magnetic field plays pivotal in shaping physical properties.