Raman Investigation, Second Harmonic Generation, and Ultrasensitive Photoresponse of Low Symmetry Transition Metal Halide PdBr 2

作者：Wanli Zhu, Weili Zhen, Rui Niu, Keke Jiao, Ranran Zhang, Lei Zhang, Fei Xue, Changjin Zhang · 发表于：ACS Photonics · 年份：2023 · DOI：10.1021/acsphotonics.3c01352 · 被引用次数：8 · 研究领域：2D Materials and Applications、Perovskite Materials and Applications、Ga2O3 and related materials

Palladium bromide (PdBr 2 ), a recent-reported narrow band gap transition metal halide semiconductor with a one-dimensional (1D) van der Waals structure, exhibits great potential in electronics, optoelectronics, and sensors. Here, we systematically study the phonon modes of PdBr 2 by using angle-resolved polarized Raman spectroscopy and temperature-dependent Raman spectroscopy. PdBr 2 exhibits strong anisotropic phonon vibrations and extremely weak interlayer coupling, arising from its low-symmetry crystal structure and natural quasi-1D properties. Intriguingly, centrosymmetric PdBr 2 crystals exhibit a significant second harmonic generation (SHG) response. Through exhaustive angle-resolved polarized SHG measurements, we trace its origin to local inversion symmetry breaking. Meanwhile, an excellent broadband photodetector based on PdBr 2 nanoflakes (from 405 to 940 nm) and a high-performance gate-tunable single-nanowire-based phototransistor have been constructed (the responsivity and specific detectivity can be as high as 2.2 × 10 6 A W –1 and 6.3 × 10 16 Jones, respectively). These parameters surpass most counterparts built of low-dimensional materials. Our findings make PdBr 2 an excellent candidate for multifunction integration in photoelectric integrated circuits or future on-chip anisotropic optoelectronic devices.