准一维层状半导体Nb_(4)P_(2)S_(21)单晶的面内光学各向异性  

In-plane optical anisotropy of quasi-one-dimensional layered semiconductor Nb_(4)P_(2)S_(21)single crystal

作　　者：程秋振 黄引 李玉辉 张凯 冼国裕 刘鹤元 车冰玉 潘禄禄 韩烨超 祝轲 齐琦 谢耀锋 潘金波 陈海龙[2,3] 李永峰 郭辉[2,3] 杨海涛 高鸿钧[2,3,4] Cheng Qiu-Zhen;Huang Yin;Li Yu-Hui;Zhang Kai;Xian Guo-Yu;Liu He-Yuan;Che Bing-Yu;Pan Lu-Lu;Han Ye-Chao;Zhu Ke;Qi Qi;Xie Yao-Feng;Pan Jin-Bo;Chen Hai-Long;Li Yong-Feng;Guo Hui;Yang Hai-Tao;Gao Hong-Jun(State Key Laboratory of Heavy Oil Processing,China University of Petroleum,Beijing 102249,China;Institute of Physics,Chinese Academy of Sciences,Beijing 100190,China;School of Physical Sciences,University of Chinese Academy of Sciences,Beijing 100190,China;Songshan Lake Materials Laboratory,Dongguan 523808,China)

机构地区：[1]中国石油大学(北京)重质油国家重点实验室,北京102249 [2]中国科学院物理研究所,北京100190 [3]中国科学院大学物理科学学院,北京100190 [4]东莞松山湖材料实验室,东莞523808

出　　处：《物理学报》2023年第21期351-359,共9页Acta Physica Sinica

基　　金：中国科学院战略性先导科技专项(批准号:XDB33030100);国家重点研发计划(批准号:2022YFA1204104);国家自然科学基金(批准号:61888102,22238012,22178384)资助的课题.

摘　　要：过渡金属磷硫化合物MPS(M为过渡金属)是一类新型二维范德瓦耳斯材料,因其独特的磁学、光学和光电性能而得到广泛关注.其中,Nb_(4)P_(2)S_(21)是具有准一维链状结构的层状材料,其各向异性的光学性质等物性仍缺乏深入研究.本文主要通过偏振Raman光谱和角度依赖的飞秒瞬态吸收光谱对Nb_(4)P_(2)S_(21)单晶的光学各向异性进行研究,Nb_(4)P_(2)S_(21)单晶的偏振Raman光谱表明在平行和垂直极化构型下,202 cm^(-1)处的Raman振动峰强度均表现出二重对称性,而489 cm^(-1)处的Raman振动峰强度均表现出四重对称性.而超快载流子动力学研究表明在平行极化构型下,Nb_(4)P_(2)S_(21)单晶在光激发后的热载流子数目和弛豫速率均表现出各向异性.这些结果有助于理解Nb_(4)P_(2)S_(21)单晶的面内各向异性光学性质,并将进一步促进其在角度关联的低维光电子器件中的应用.Transition-metal phosphorous chalcogenide MPS(M=transition metal),an emerging type of two-dimensional(2D)van der Waals material with the unique optical and opto-electronic properties,has received much attention.The quasi-one-dimensional chain structure of Nb_(4)P_(2)S_(21)will possess the strong anisotropic optical and photoelectric properties.Therefore,the single crystal and low-dimensional materials of Nb_(4)P_(2)S_(21)have potential applications in new polarization controllers,polarization-sensitive photoelectronic detectors,etc.However,there is still a lack of research on the anisotropic optical properties of the high-quality Nb_(4)P_(2)S_(21)single crystals.Herein,the millimeter-sized Nb_(4)P_(2)S_(21)single crystals are successfully prepared by the chemical vapor transport method.The chemical composition,the crystal structure and the anisotropic optical properties of the Nb_(4)P_(2)S_(21)single crystals are carefully analyzed.The energy dispersive X-ray spectroscopy results show that the element distribution is uniform and the element ratio is close to the stoichiometric ratio.The X-ray diffraction and the transmission electron microscopy results show a good crystallinity.The absorption spectra shows that the optical band gap of the Nb_(4)P_(2)S_(21)single crystal is 1.8 eV.Interestingly,the Nb_(4)P_(2)S_(21)single crystal can be mechanically exfoliated to obtain few-layer material.The thickness-dependent Raman spectra show that the Raman vibration peaks of bulk and few-layer Nb_(4)P_(2)S_(21)each have only a weak shift,indicating a weak interlayer interaction in the Nb_(4)P_(2)S_(21)single crystal.In order to make an in-depth study of the optical properties of Nb_(4)P_(2)S_(21)single crystals,the polarized-dependent Raman spectra and the femtosecond transient absorption(TA)spectra by using pump pulses and probe pulses with a wavelength of 400 nm and a wavelength range of 500–700 nm are recorded.Importantly,the polarized-dependent Raman scattering spectra with the angle-dependent measurements reveal that

关 键 词：Nb_(4)P_(2)S_(21) 偏振Raman 超快载流子动力学 光学各向异性 

分 类 号：TN304[电子电信—物理电子学]