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    Optical properties of phosphorene
    Jiong Yang, Yuerui Lu(卢曰瑞)
    Chin. Phys. B, 2017, 26 (3): 034201.   DOI: 10.1088/1674-1056/26/3/034201
    Abstract549)   HTML    PDF (1568KB)(776)      

    Phosphorene is a two-dimensional semiconductor with layers-dependent bandgap in the near-infrared range and it has attracted a great deal of attention due to its high anisotropy and carrier mobility. The highly anisotropic nature of phosphorene has been demonstrated through Raman and polarization photoluminescence measurements. Photoluminescence spectroscopy has also revealed the layers-dependent bandgap of phosphorene. Furthermore, due to the reduced dimensionality and screening in phosphorene, excitons and trions can stably exist at elevated temperatures and have large binding energies. The exciton and trion dynamics are thus detected by applying electrical bias or optical injection to the phosphorene system. Finally, various optical and optoelectronic applications based on phosphorene have been demonstrated and discussed.

    Light-matter interaction of 2D materials: Physics and device applications
    Zi-Wei Li(李梓维), Yi-Han Hu(胡义涵), Yu Li(李瑜), Zhe-Yu Fang(方哲宇)
    Chin. Phys. B, 2017, 26 (3): 036802.   DOI: 10.1088/1674-1056/26/3/036802
    Abstract542)   HTML    PDF (5688KB)(1111)      

    In the last decade, the rise of two-dimensional (2D) materials has attracted a tremendous amount of interest for the entire field of photonics and opto-electronics. The mechanism of light-matter interaction in 2D materials challenges the knowledge of materials physics, which drives the rapid development of materials synthesis and device applications. 2D materials coupled with plasmonic effects show impressive optical characteristics, involving efficient charge transfer, plasmonic hot electrons doping, enhanced light-emitting, and ultrasensitive photodetection. Here, we briefly review the recent remarkable progress of 2D materials, mainly on graphene and transition metal dichalcogenides, focusing on their tunable optical properties and improved opto-electronic devices with plasmonic effects. The mechanism of plasmon enhanced light-matter interaction in 2D materials is elaborated in detail, and the state-of-the-art of device applications is comprehensively described. In the future, the field of 2D materials holds great promise as an important platform for materials science and opto-electronic engineering, enabling an emerging interdisciplinary research field spanning from clean energy to information technology.

    Topological transport in Dirac electronic systems: A concise review
    Hua-Ding Song(宋化鼎), Dian Sheng(盛典), An-Qi Wang(王安琦), Jin-Guang Li(李金光), Da-Peng Yu(俞大鹏), Zhi-Min Liao(廖志敏)
    Chin. Phys. B, 2017, 26 (3): 037301.   DOI: 10.1088/1674-1056/26/3/037301
    Abstract431)   HTML    PDF (8290KB)(1352)      

    Various novel physical properties have emerged in Dirac electronic systems, especially the topological characters protected by symmetry. Current studies on these systems have been greatly promoted by the intuitive concepts of Berry phase and Berry curvature, which provide precise definitions of the topological phases. In this topical review, transport properties of topological insulator (Bi2Se3), topological Dirac semimetal (Cd3As2), and topological insulator-graphene heterojunction are presented and discussed. Perspectives about transport properties of two-dimensional topological nontrivial systems, including topological edge transport, topological valley transport, and topological Weyl semimetals, are provided.

    Graphene resistive random memory–the promising memory device in next generation
    Xue-Feng Wang(王雪峰), Hai-Ming Zhao(赵海明), Yi Yang(杨轶), Tian-Ling Ren(任天令)
    Chin. Phys. B, 2017, 26 (3): 038501.   DOI: 10.1088/1674-1056/26/3/038501
    Abstract405)   HTML    PDF (5614KB)(1247)      

    Graphene-based resistive random access memory (GRRAM) has grasped researchers' attention due to its merits compared with ordinary RRAM. In this paper, we briefly review different types of GRRAMs. These GRRAMs can be divided into two categories: graphene RRAM and graphene oxide (GO)/reduced graphene oxide (rGO) RRAM. Using graphene as the electrode, GRRAM can own many good characteristics, such as low power consumption, higher density, transparency, SET voltage modulation, high uniformity, and so on. Graphene flakes sandwiched between two dielectric layers can lower the SET voltage and achieve multilevel switching. Moreover, the GRRAM with rGO and GO as the dielectric or electrode can be simply fabricated. Flexible and high performance RRAM and GO film can be modified by adding other materials layer or making a composite with polymer, nanoparticle, and 2D materials to further improve the performance. Above all, GRRAM shows huge potential to become the next generation memory.

    Graphene integrated photodetectors and opto-electronic devices–a review
    Xiaomu Wang(王肖沐), Xuetao Gan(甘雪涛)
    Chin. Phys. B, 2017, 26 (3): 034203.   DOI: 10.1088/1674-1056/26/3/034203
    Abstract421)   HTML    PDF (2127KB)(728)      

    Graphene and other two-dimensional materials have recently emerged as promising candidates for next-generation, high-performance photonics. In this paper, the progress of research into photodetectors and other electro-optical devices based on graphene integrated silicon photonics is briefly reviewed. We discuss the performance metrics, photo-response mechanisms, and experimental results of the latest graphene photodetectors integrated with silicon photonics. We also lay out the unavoidable performance trade-offs in meeting the requirements of various applications. In addition, we describe other opto-electronic devices based on this idea. Integrating two-dimensional materials with a silicon platform provides new opportunities in advanced integrated photonics.

    Atomic crystals resistive switching memory
    Chunsen Liu(刘春森), David Wei Zhang(张卫), Peng Zhou(周鹏)
    Chin. Phys. B, 2017, 26 (3): 033201.   DOI: 10.1088/1674-1056/26/3/033201
    Abstract596)   HTML    PDF (11820KB)(1046)      

    Facing the growing data storage and computing demands, a high accessing speed memory with low power and non-volatile character is urgently needed. Resistive access random memory with 4F2 cell size, switching in sub-nanosecond, cycling endurances of over 1012 cycles, and information retention exceeding 10 years, is considered as promising next-generation non-volatile memory. However, the energy per bit is still too high to compete against static random access memory and dynamic random access memory. The sneak leakage path and metal film sheet resistance issues hinder the further scaling down. The variation of resistance between different devices and even various cycles in the same device, hold resistive access random memory back from commercialization. The emerging of atomic crystals, possessing fine interface without dangling bonds in low dimension, can provide atomic level solutions for the obsessional issues. Moreover, the unique properties of atomic crystals also enable new type resistive switching memories, which provide a brand-new direction for the resistive access random memory.

    Two-dimensional materials for ultrafast lasers
    Fengqiu Wang(王枫秋)
    Chin. Phys. B, 2017, 26 (3): 034202.   DOI: 10.1088/1674-1056/26/3/034202
    Abstract393)   HTML    PDF (6019KB)(1009)      

    As the fundamental optical properties and novel photophysics of graphene and related two-dimensional (2D) crystals are being extensively investigated and revealed, a range of potential applications in optical and optoelectronic devices have been proposed and demonstrated. Of the many possibilities, the use of 2D materials as broadband, cost-effective and versatile ultrafast optical switches (or saturable absorbers) for short-pulsed lasers constitutes a rapidly developing field with not only a good number of publications, but also a promising prospect for commercial exploitation. This review primarily focuses on the recent development of pulsed lasers based on several representative 2D materials. The comparative advantages of these materials are discussed, and challenges to practical exploitation, which represent good future directions of research, are laid out.

    Band gap engineering of atomically thin two-dimensional semiconductors
    Cui-Huan Ge(葛翠环), Hong-Lai Li(李洪来), Xiao-Li Zhu(朱小莉), An-Lian Pan(潘安练)
    Chin. Phys. B, 2017, 26 (3): 034208.   DOI: 10.1088/1674-1056/26/3/034208
    Abstract392)   HTML    PDF (7933KB)(3063)      

    Atomically thin two-dimensional (2D) layered materials have potential applications in nanoelectronics, nanophotonics, and integrated optoelectronics. Band gap engineering of these 2D semiconductors is critical for their broad applications in high-performance integrated devices, such as broad-band photodetectors, multi-color light emitting diodes (LEDs), and high-efficiency photovoltaic devices. In this review, we will summarize the recent progress on the controlled growth of composition modulated atomically thin 2D semiconductor alloys with band gaps tuned in a wide range, as well as their induced applications in broadly tunable optoelectronic components. The band gap engineered 2D semiconductors could open up an exciting opportunity for probing their fundamental physical properties in 2D systems and may find diverse applications in functional electronic/optoelectronic devices.

    Thermal properties of two-dimensional materials
    Gang Zhang(张刚), Yong-Wei Zhang(张永伟)
    Chin. Phys. B, 2017, 26 (3): 034401.   DOI: 10.1088/1674-1056/26/3/034401
    Abstract421)   HTML    PDF (4492KB)(1170)      

    Two-dimensional (2D) materials, such as graphene, phosphorene, and transition metal dichalcogenides (e.g., MoS2 and WS2), have attracted a great deal of attention recently due to their extraordinary structural, mechanical, and physical properties. In particular, 2D materials have shown great potential for thermal management and thermoelectric energy generation. In this article, we review the recent advances in the study of thermal properties of 2D materials. We first review some important aspects in thermal conductivity of graphene and discuss the possibility to enhance the ultra-high thermal conductivity of graphene. Next, we discuss thermal conductivity of MoS2 and the new strategy for thermal management of MoS2 device. Subsequently, we discuss the anisotropic thermal properties of phosphorene. Finally, we review the application of 2D materials in thermal devices, including thermal rectifier and thermal modulator.

    Cited: Web of science (54)
    Photodetecting and light-emitting devices based on two-dimensional materials
    Yuanfang Yu(于远方), Feng Miao(缪峰), Jun He(何军), Zhenhua Ni(倪振华)
    Chin. Phys. B, 2017, 26 (3): 036801.   DOI: 10.1088/1674-1056/26/3/036801
    Abstract328)   HTML    PDF (7301KB)(933)      

    Two-dimensional (2D) materials, e.g., graphene, transition metal dichalcogenides (TMDs), and black phosphorus (BP), have demonstrated fascinating electrical and optical characteristics and exhibited great potential in optoelectronic applications. High-performance and multifunctional devices were achieved by employing diverse designs, such as hybrid systems with nanostructured materials, bulk semiconductors and organics, forming 2D heterostructures. In this review, we mainly discuss the recent progress of 2D materials in high-responsive photodetectors, light-emitting devices and single photon emitters. Hybrid systems and van der Waals heterostructure-based devices are emphasized, which exhibit great potential in state-of-the-art applications.

    Recent progress on integrating two-dimensional materials with ferroelectrics for memory devices and photodetectors
    Jianlu Wang(王建禄), Weida Hu(胡伟达)
    Chin. Phys. B, 2017, 26 (3): 037106.   DOI: 10.1088/1674-1056/26/3/037106
    Abstract360)   HTML    PDF (3372KB)(1044)      

    Two-dimensional (2D) materials, such as graphene and MoS2 related transition metal dichalcogenides (TMDC), have attracted much attention for their potential applications. Ferroelectrics, one of the special and traditional dielectric materials, possess a spontaneous electric polarization that can be reversed by the application of an external electric field. In recent years, a new type of device, combining 2D materials with ferroelectrics, has been fabricated. Many novel devices have been fabricated, such as low power consumption memory devices, highly sensitive photo-transistors, etc. using this technique of hybrid systems incorporating ferroelectrics and 2D materials. This paper reviews two types of devices based on field effect transistor (FET) structures with ferroelectric gate dielectric construction (termed FeFET). One type of device is for logic applications, such as a graphene and TMDC FeFET for fabricating memory units. Another device is for optoelectric applications, such as high performance phototransistors using a graphene p-n junction. Finally, we discuss the prospects for future applications of 2D material FeFET.

    Photodetectors based on junctions of two-dimensional transition metal dichalcogenides
    Xia Wei(魏侠), Fa-Guang Yan(闫法光), Chao Shen(申超), Quan-Shan Lv(吕全山), Kai-You Wang(王开友)
    Chin. Phys. B, 2017, 26 (3): 038504.   DOI: 10.1088/1674-1056/26/3/038504
    Abstract360)   HTML    PDF (7098KB)(792)      

    Transition metal dichalcogenides (TMDCs) have gained considerable attention because of their novel properties and great potential applications. The flakes of TMDCs not only have great light absorption from visible to near infrared, but also can be stacked together regardless of lattice mismatch like other two-dimensional (2D) materials. Along with the studies on intrinsic properties of TMDCs, the junctions based on TMDCs become more and more important in applications of photodetection. The junctions have shown many exciting possibilities to fully combine the advantages of TMDCs, other 2D materials, conventional and organic semiconductors together. Early studies have greatly enriched the application of TMDCs in photodetection. In this review, we investigate the efforts in photodetectors based on the junctions of TMDCs and analyze the properties of those photodetectors. Homojunctions based on TMDCs can be made by surface chemical doping, elemental doping and electrostatic gating. Heterojunction formed between TMDCs/2D materials, TMDCs/conventional semiconductors and TMDCs/organic semiconductor also deserve more attentions. We also compare the advantages and disadvantages of different junctions, and then give the prospects for the development of junctions based on TMDCs.

    Geometric stability and electronic structure of infinite and finite phosphorus atomic chains
    Jingsi Qiao(乔婧思), Linwei Zhou(周霖蔚), Wei Ji(季威)
    Chin. Phys. B, 2017, 26 (3): 036803.   DOI: 10.1088/1674-1056/26/3/036803
    Abstract394)   HTML    PDF (2054KB)(385)      

    One-dimensional mono- or few-atomic chains were successfully fabricated in a variety of two-dimensional materials, like graphene, BN, and transition metal dichalcogenides, which exhibit striking transport and mechanical properties. However, atomic chains of black phosphorus (BP), an emerging electronic and optoelectronic material, is yet to be investigated. Here, we comprehensively considered the geometry stability of six categories of infinite BP atomic chains, transitions among them, and their electronic structures. These categories include mono- and dual-atomic linear, armchair, and zigzag chains. Each zigzag chain was found to be the most stable in each category with the same chain width. The mono-atomic zigzag chain was predicted as a Dirac semi-metal. In addition, we proposed prototype structures of suspended and supported finite atomic chains. It was found that the zigzag chain is, again, the most stable form and could be transferred from mono-atomic armchair chains. An orientation dependence was revealed for supported armchair chains that they prefer an angle of roughly 35°-37° perpendicular to the BP edge, corresponding to the [110] direction of the substrate BP sheet. These results may promote successive research on mono- or few-atomic chains of BP and other two-dimensional materials for unveiling their unexplored physical properties.

    A review for compact model of graphene field-effect transistors
    Nianduan Lu(卢年端), Lingfei Wang(汪令飞), Ling Li(李泠), Ming Liu(刘明)
    Chin. Phys. B, 2017, 26 (3): 036804.   DOI: 10.1088/1674-1056/26/3/036804
    Abstract298)   HTML    PDF (10934KB)(1142)      

    Graphene has attracted enormous interests due to its unique physical, mechanical, and electrical properties. Specially, graphene-based field-effect transistors (FETs) have evolved rapidly and are now considered as an option for conventional silicon devices. As a critical step in the design cycle of modern IC products, compact model refers to the development of models for integrated semiconductor devices for use in circuit simulations. The purpose of this review is to provide a theoretical description of current compact model of graphene field-effect transistors. Special attention is devoted to the charge sheet model, drift-diffusion model, Boltzmann equation, density of states (DOS), and surface-potential-based compact model. Finally, an outlook of this field is briefly discussed.

    Toward high-performance two-dimensional black phosphorus electronic and optoelectronic devices
    Xuefei Li(李学飞), Xiong Xiong(熊雄), Yanqing Wu(吴燕庆)
    Chin. Phys. B, 2017, 26 (3): 037307.   DOI: 10.1088/1674-1056/26/3/037307
    Abstract309)   HTML    PDF (5935KB)(424)      

    Recently, black phosphorus (BP) has joined the two-dimensional material family as a promising candidate for electronic and photonic applications due to its moderate bandgap, high carrier mobility, and unusual in-plane anisotropy. Here, we review recent progress in BP-based devices, such as field-effect transistors, contact resistance, quantum transport, stability, photodetector, heterostructure, and in-plane anisotropy. We also give our perspectives on future BP research directions.

    Review of ultrafast spectroscopy studies of valley carrier dynamics in two-dimensional semiconducting transition metal dichalcogenides
    Dong Sun(孙栋), Jia-Wei Lai(赖佳伟), Jun-Chao Ma(马骏超), Qin-Sheng Wang(王钦生), Jing Liu (刘晶)
    Chin. Phys. B, 2017, 26 (3): 037801.   DOI: 10.1088/1674-1056/26/3/037801
    Abstract242)   HTML    PDF (4761KB)(826)      

    The two-dimensional layered transition metal dichalcogenides provide new opportunities in future valley-based information processing and also provide an ideal platform to study excitonic effects. At the center of various device physics toward their possible electronic and optoelectronic applications is understanding the dynamical evolution of various many-particle electronic states, especially exciton which dominates the optoelectronic response of TMDs, under the novel context of valley degree of freedom. Here, we provide a brief review of experimental advances in using helicity-resolved ultrafast spectroscopy, especially ultrafast pump-probe spectroscopy, to study the dynamical evolution of valley-related many-particle electronic states in semiconducting monolayer transitional metal dichalcogenides.