Optically confined polarized resonance Raman studies in identifying crystalline orientation of sub-diffraction limited AlGaN nanostructure

Abstract

An optical characterization tool of Raman spectroscopy with extremely weak scattering cross section tool is not popular to analyze scattered signal from a single nanostructure in the subdiffraction regime. In this regard, plasmonic assisted characterization tools are only relevant in spectroscopic studies of nanoscale object in the sub-diffraction limit. We have reported polarized resonance Raman spectroscopic (RRS) studies with strong electron-phonon coupling to understand the crystalline orientation of a single AlGaN nanowire of diameter ~100 nm. AlGaN nanowire is grown by chemical vapor deposition technique using the catalyst assisted vapor-liquid-solid process. The results are compared with the high resolution transmission electron microscopic analysis. As a matter of fact, optical confinement effect due to the dielectric contrast of nanowire with respect to that of surrounding media assisted with electron-phonon coupling of RRS are useful for the spectroscopic analysis in the sub-diffraction limit of 325 nm (/2N.A.) using an excitation wavelength () of 325 nm and near ultraviolet 40Х far field objective with a numerical aperture (N.A.) value of 0.50.

Far field photoluminescence imaging of single AlGaN nanowire in the sub‐wavelength scale using confinement of polarized light

“…The evanescent waves near to the metal‐dielectric interface assist the imaging or focusing of nanostructures in the sub‐diffraction length scale. Recently, polarized Raman studies of semiconductor nanostructures, using optically confined polarized light in dielectric contrast with surrounding media, has raised considerable interests in the scientific community. The rate of interaction of a light emitting material with electromagnetic radiation can be enhanced by keeping it in a micro‐cavity.…”

Polarized Raman and photoluminescence studies of a sub-micron sized hexagonal AlGaN crystallite for structural and optical properties

“…S3. According to the polarization selection rule in the backscattering configuration, the possible configurations and corresponding allowed modes for a wurtzite [0001] oriented GaN (Z||[0001]) are given in the Table …”

“…According to the polarization selection rule in the backscattering configuration, the possible configurations and corresponding allowed modes for a wurtzite [0001] oriented GaN (Z||[0001]) are given in the Table 1. [15,16,[20][21][22][23][24] From Table 1, it is very easy to figure out the possible crystalline orientations from the polarization configurations corresponding to its allowed Raman modes obtained from the different polarization conditions of incident and scattered waves keeping consistency with the Raman selection rules. For example, from Table 1, it is obvious that the possible configurations for the combinations of Raman modes E H 2 and A 1 (LO) in one polarization condition and E H 2 in the cross polarization ( Fig.…”

“…In addition to the optical properties, the polar nature of wurtzite crystals find piezoelectric applications, which has been widely utilized for electromechanical sensing, energy harvesting for self‐powered devices, micro‐actuators, micro‐sensors, ultrasonic motors, micro‐pumps, and few MEMS applications . In the context of understanding the crystalline properties of the sub‐micron sized cystallite, the Raman spectroscopy is not only a very efficient non‐destructive characterization tool for the phase confirmation of the sample but also the fact that the polarized Raman spectrum is capable to investigate the crystallographic orientation in agreement with selection rules . There are several reports available for polarized as well as angular dependent polarized Raman studies collected from a single spot on material .…”

The light–matter interaction of a single semiconducting AlGaN nanowire and noble metal Au nanoparticles in the sub-diffraction limit

“…Similarly, the presence of unavoidable impurity of C, in the sample, produces the C N -V Ga complex which also may act as a deep acceptor leading to the PL emission peak centered at 1.76 eV ( Figure 6(b)) for recombination of electrons from the shallow donor state of V N , [27,28]. The peaks observed at 3.78 and 3.73 eV are assigned to multi-phonon modes of first order, A 1 (LO) and corresponding second order 2A 1 (LO) Raman modes of wurtzite AlGaN, respectively [1,25]. The interaction of single AlGaN NW with light in the near-field regime is realized by using the help of possible energy levels in the schematic representation of band-diagram ( Figure 6(b)).…”