Raman Spectroscopy of the Trapezoidal Bi<sub>2</sub>O<sub>2</sub>Se
Mengwei Han, Shengqiang Wu, Xiaoxu Zhao, Qinming He, Bangmin Zhang, Weiming Xiong, Xin Luo, Yue Zheng
Abstract
Abstract The 2D Bi 2 O 2 Se has recently attracted significant interest with large Hall mobility at low temperature due to the depressed electron–phonon scattering. However, the phonon properties of Bi 2 O 2 Se are not well explored, and some Raman modes are under debate. Here, substrate engineering is used to grow an unexplored trapezoidal Bi 2 O 2 Se, which facilitates the Raman measurements in different orientation planes. Two additional Raman modes at 55 and 429 cm −1 are detected on the slope of the trapezoid besides the 159 and 362 cm −1 modes found on the top plane of the trapezoidal Bi 2 O 2 Se. Based on the polarized Raman spectroscopy, density functional theory calculations, and group theory analysis, the Raman modes of 55, 159, 362, and 429 cm −1 are assigned to the E g , A 1g , B 1g , and E g modes, respectively. There are two distinct types of angle‐resolved polarized Raman spectroscopy for the A 1g mode on the top and edge planes of Bi 2 O 2 Se, which can be used to determine the crystal orientation unambiguously. Furthermore, strong thermal anisotropy is found in the top and edge planes of trapezoidal Bi 2 O 2 Se, as reflected from the first‐order temperature coefficient of A 1g phonon mode. The novel growth strategy and interesting anisotropic phonon properties may open up potential applications of Bi 2 O 2 Se in nanoelectronics.