Crystalline Orientation Identification of Phosphorene Using Polarized Raman Spectroscopy without Analyzer

Abstract

The unique photoelectric properties of phosphorene typically include anisotropy, hence the nondestructive and rapid identification of its crystal orientation is a key point to the investigation and application of phosphorene. Currently, the orientation identification by analyzing the Ag1 mode based on parallel-polarized Raman has severe requirements for the applicable Raman system. Therefore, it is necessary to develop a more general, convenient, and accurate method for determining the crystal orientation of phosphorene. In this paper, a method of orientation identification was proposed by using a Raman system without an analyzer and quantifying the correlation between the intensities of Ag1 and Ag2 modes with the change of the incident polarization direction. By using mechanically peeled phosphorene as specimens, Raman measurements were carried out under the Raman configurations of both parallel polarization and with no analyzer. The results show that the crystal orientation of phosphorene can be accurately identified by quantifying the Raman intensities of both Ag1 and Ag2 modes using the Raman system without an analyzer.

Crystalline Orientation Identification of Multilayer Black Phosphorus Based on the Ag1 and Ag2 Raman Modes for an Orthogonally Polarized Configuration

“…In the OP configuration, the polarization directions of the incident laser and scattering light are perpendicular to each other, and the angle between the incident laser and X direction is φ; hence, the polarization vector of the incident laser and scattering light, with respect to the crystalline axis, is expressed as e i = [sin­(φ – θ), 0, cos­(φ – θ)] and e s = [cos­(φ – θ), 0, – sin­(φ – θ)], respectively. Therefore, the expression of the Raman scattering intensity of the two A g modes under the OP and PP is given by eqs and , , respectively: where f is a constant related to interference enhancement, and the constant K is determined by the effect of partial depolarization where ϕ ca = ϕ c – ϕ a is the phase difference between the complex Raman tensor elements c and a .…”

“…The A g 2 and A g 1 data under the PP configuration are shown in Figures and , respectively. The curves of the data were fitted by using the equations given by (eq ) under OP and (eq ) under PP . In all the resulting figures, the solid square points are the experimental data, and the curves are the fitted results.…”

Orientation Identification of the Black Phosphorus with Different Thickness Based on B2g Mode Using a Micro-Raman Spectroscope under a Nonanalyzer Configuration

“…The experimental data of the B 2g mode under the PP and NA configurations were fitted by using Equations (8) and (10), and the fitting results are given as the I B-PP and I B-NA curves in Figure 4 a,c, respectively. Similarly, the experimental data of the A g 2 mode under the PP and NA configurations were fitted by the models given in published papers [ 47 ], and the results are given as the I A2-PP and I A2-NA curves in Figure 4 b,d, respectively.…”

“…Previous studies have pointed out that the A g 2 mode is affected by the thicknesses of black phosphorus when identifying crystalline orientations. Our previous work [ 47 ] identified the crystalline orientation through A g 1 and A g 2 modes under the NA configuration.…”

“…Figure 6 shows the B 2g intensity data under the NA configuration (left) and A g 2 intensity data under the PP configuration (right) of all sampling spots, where the square points are the experimental data and solid lines are I B-NA ( φ , θ ) and I A2-PP curves fitted using Equation (10) and Equation [ 47 ], respectively, based on the experimental data of all sampling spots. Table 2 lists the identification results of the ZZ directions for all the sampling spots using the traditional method (based on the A g 2 mode under the PP configuration) and the proposed method (based on the B 2g mode under the NA configuration).…”