半导体学报2017年38卷3期——二维材料与器件专题

二维材料与器件专题

自从2004年Novoselov和Geim成功制备石墨烯以来，二维材料因其新颖的物理性质以及广阔的应用前景吸引了人们极大的研究兴趣。

《半导体学报》组织了“二维材料与器件”专题，由中科院半导体研究所李京波研究员和南京大学王欣然教授担任特约编辑，该专题已于2017年第3期正式出版！该专题有5篇关于二维氮化硼制备、过渡金属硫化物拉曼性质以及范德瓦尔斯异质结等领域的文献综述。此外还有7篇研究论文，方向包括多种二维材料的制备及成像、光响应、掺杂、能带调控以及量子输运等。这些课题都是二维材料领域当前及将来的主要研究方向。

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Jingbo Li and Xinran Wang

2017 J. Semicond. 38 031001

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Nengjie Huo, Yujue Yang and Jingbo Li

2017 J. Semicond. 38 0310022D materials including graphene and TMDs have proven interesting physical properties and promising optoelectronic applications. We reviewed the growth, characterization and optoelectronics based on 2D TMDs and their heterostructures, and demonstrated their unique and high quality of performances. For example, we observed the large mobility, fast response and high photo-responsivity in MoS₂, WS₂ and WSe₂ phototransistors, as well as the novel performances in vdW heterostructures such as the strong interlayer coupling, am-bipolar and rectifying behaviour, and the obvious photovoltaic effect. It is being possible that 2D family materials could play an increasingly important role in the future nano- and opto-electronics, more even than traditional semiconductors such as silicon.

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Haolin Wang, Yajuan Zhao, Yong Xie, Xiaohua Ma and Xingwang Zhang

2017 J. Semicond. 38 031003

Two-dimensional (2D) materials have recently received a great deal of attention due to their unique structures and fascinating properties, as well as their potential applications. 2D hexagonal boron nitride (2D h-BN), an insulator with excellent thermal stability, chemical inertness, and unique electronic and optical properties, and a band gap of 5.97 eV, is considered to be an ideal candidate for integration with other 2D materials. Nevertheless, the controllable growth of high-quality 2D h-BN is still a great challenge. A comprehensive overview of the progress that has been made in the synthesis of 2D h-BN is presented, highlighting the advantages and disadvantages of various synthesis approaches. In addition, the electronic, optical, thermal, and mechanical properties, heterostructures, and related applications of 2D h-BN are discussed.

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Huihui Yang, Feng Gao, Mingjin Dai, Dechang Jia, Yu Zhou and Pingan Hu

2017 J. Semicond. 38 031004

Two-dimensional (2D) layered materials, such as graphene, hexagonal boron nitride (h-BN), molybdenum disulfide (MoS₂), have attracted tremendous interest due to their atom-thickness structures and excellent physical properties. h-BN has predominant advantages as the dielectric substrate in FET devices due to its outstanding properties such as chemically inert surface, being free of dangling bonds and surface charge traps, especially the large-band-gap insulativity. h-BN involved vertical heterostructures have been widely exploited during the past few years. Such heterostructures adopting h-BN as dielectric layers exhibit enhanced electronic performance, and provide further possibilities for device engineering. Besides, a series of intriguing physical phenomena are observed in certain vertical heterostructures, such as superlattice potential induced replication of Dirac points, band gap tuning, Hofstadter butterfly states, gate-dependent pseudospin mixing. Herein we focus on the rapid developments of h-BN synthesis and fabrication of vertical heterostructures devices based on h-BN, and review the novel properties as well as the potential applications of the heterostructures composed of h-BN.

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Chao Li, Peng Zhou and David Wei Zhang

2017 J. Semicond. 38 031005

Van der Waals heterostructures, composed of individual two-dimensional material have been developing extremely fast. Synthesis of van der Waals heterostructures without the constraint of lattice matching and processing compatibility provides an ideal platform for fundamental research and new device exploitation. We review the approach of synthesis of van der Waals heterostructures, discuss the property of heterostructures and thoroughly illustrate the functional van der Waals heterostructures used in novel electronic and photoelectronic device.

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Qing-Hai Tan, Xin Zhang, Xiang-Dong Luo, Jun Zhang and Ping-Heng Tan

2017 J. Semicond. 38 031006

Two-dimensional transition metal dichalcogenides (TMDs) have attracted extensive attention due to their many novel properties. The atoms within each layer in two-dimensional TMDs are joined together by covalent bonds, while van der Waals interactions combine the layers together. This makes its lattice dynamics layer-number dependent. The evolutions of ultralow frequency (<50 cm^-1) modes, such as shear and layer-breathing modes have been well-established. Here, we review the layer-number dependent high-frequency (>50 cm^-1) vibration modes in few-layer TMDs and demonstrate how the interlayer coupling leads to the splitting of high-frequency vibration modes, known as Davydov splitting. Such Davydov splitting can be well described by a van der Waals model, which directly links the splitting with the interlayer coupling. Our review expands the understanding on the effect of interlayer coupling on the high-frequency vibration modes in TMDs and other two-dimensional materials.

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Jimin Shang, Le Huang and Zhongming Wei

2017 J. Semicond. 38 033001

Using first-principles calculations, including Grimme D2 method for van der Waals interactions, we investigate the tuning electronic properties of bilayer zirconium disulfides (ZrS₂) subjected to vertical electric field and normal compressive strain. The band gap of ZrS₂ bilayer can be flexibly tuned by vertical external electric field. Due to the Stark effect, at critical electric fields about 1.4 V/Å, semiconducting-metallic transition presents. In addition, our results also demonstrated that the compressive strain has an important impact on the electronic properties of ZrS₂ bilayer sheet. The widely tunable band gaps confirm possibilities for its applications in electronics and optoelectronics.

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Hanming Zhou, Xiao Lin, Hongwei Guo, Shisheng Lin, Yiwei Sun and Yang Xu

2017 J. Semicond. 38 033002

Two-dimensional silicon carbide (2d-SiC) is a viable material for next generation electronics due to its moderate, direct bandgap with huge potential. In particular, its potential for p-n junctions is yet to be explored. In this paper, three types of 2d-SiC-based p-n junctions with different doping configuration are modeled. The doping configurations refer to partially replacing carbon with boron or nitrogen atoms along the zigzag or armchair direction, respectively. By employing density functional theory, we calculate the transport properties of the SiC based p-n junctions and obtain negative differential resistance and high rectification ratio. We also find that the junction along the zigzag direction with lower doping density exhibits optimized rectification performance. Our study suggests that 2d-SiC is a promising candidate as a material platform for future nano-devices.

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Yuanfang Yu, Zhenzhen Li, Wenhui Wang, Xitao Guo, Jie Jiang, Haiyan Nan and Zhenhua Ni

2017 J. Semicond. 38 033003

CVD graphene is a promising candidate for optoelectronic applications due to its high quality and high yield. However, multi-layer domains could inevitably form at the nucleation centers during the growth. Here, we propose an optical imaging technique to precisely identify the multilayer domains and also the ratio of their coverage in large-scale CVD monolayer graphene. We have also shown that the stacking disorder in twisted bilayer graphene as well as the impurities on the graphene surface could be distinguished by optical imaging. Finally, we investigated the effects of bilayer domains on the optical and electrical properties of CVD graphene, and found that the carrier mobility of CVD graphene is seriously limited by scattering from bilayer domains. Our results could be useful for guiding future optoelectronic applications of large-scale CVD graphene.

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Ce Huang, Yibo Jin, Weiyi Wang, Lei Tang, Chaoyu Song and Faxian Xiu

2017 J. Semicond. 38 033004

Recently, two-dimensional materials have been attracting increasing attention because of their novel properties and promising applications. However, the impurity doping remains a significant challenge owing to the lack of the doping strategy in the atomically thin layers. Here we report on the chromium (Cr) and manganese (Mn) doping in atomically-thin MoS₂ crystals grown by chemical vapor deposition. The Cr/Mn doped MoS₂ samples are characterized by a peak at 1.76 and 1.79 eV in photoluminescence spectra, respectively, compared with the undoped one at 1.85 eV. The field-effect transistor (FET) devices based on the Mn doping show a higher threshold voltage than that of the pure MoS₂ while the Cr doping exhibits the opposite behavior. Importantly, the carrier concentration in these samples displays a remarkable difference arising from the doping effect, consistent with the evolution of the FET performance. The temperature-dependent conductivity measurements further demonstrate a large variation in activation energy. The successful incorporation of the Mn and Cr impurities into the monolayer MoS₂ paves the way towards the high Curie temperature two-dimensional dilute magnetic semiconductors.

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Caixia Guo, Congxin Xia, Tianxing Wang and Yufang Liu

2017 J. Semicond. 38 033005

By using a combined method of density functional theory and non-equilibrium Green's function formalism, we investigate the electronic transport properties of carbon-doped armchair phosphorene nanoribbons (APNRs). The results show that C atom doping can strongly affect the electronic transport properties of the APNR and change it from semiconductor to metal. Meanwhile, obvious negative differential resistance (NDR) behaviors are obtained by tuning the doping position and concentration. In particular, with reducing doping concentration, NDR peak position can enter into mV bias range. These results provide a theoretical support to design the related nanodevice by tuning the doping position and concentration in the APNRs.

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Yan Wang, Le Huang and Zhongming Wei

2017 J. Semicond. 38 034001

2D SnS₂ nanosheets are exfoliated by micromechanical exfoliation technique from SnS₂ single crystals which are synthesized by CVT methods. Monolayer SnS₂ nanosheet has been obtained and the Raman spectrum shows that A_1g mode of monolayer SnS₂ shows a slight softening compared with bulk SnS₂ single crystal. The field effect transistors (FETs) based on multilayer SnS₂ nanosheets have been fabricated, of which the electrical and photoelectrical properties have been measured. Under dark condition, with V_sd of 1 V, our SnS₂ FET shows n-type behavior. The carrier mobility of the FETs reach 3.51 cm²V^-1s^-1 and the ‘ON/OFF’ ratio is about 5×10². The SnS₂ FET is also illuminated under 532 nm laser with the power of 500 mW/cm². The light absorption causes an increment of carrier mobility (from 3.51 cm²V^-1s^-1 under dark condition to 3.85 cm²V^-1s^-1 under 532 nm laser illumination with the power of 500 mW/cm²) of SnS₂. The responsivity (R) and detectivity of our multilayer device under 500 mW/cm² 532 nm is 2.08 A/W and 6×10⁶ J, respectively. All the above properties indicate the potential of SnS₂ nanosheets to be used as FETs and phototransistors.

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Fengjing Liu, Jiawei Wang, Liang Wang, Xiaoyong Cai, Chao Jiang and Gongtang Wang

2017 J. Semicond. 38 034002

Perovskite/MoS₂ hybrid thin film transistor photodetectors consist of few-layered MoS₂ and CH₃NH₃PbI₃ film with various thickness prepared by two-step vacuum deposition. By implementing perovskite CH₃NH₃PbI₃ film onto the MoS₂ flake, the perovskite/MoS₂ hybrid photodetector exhibited a photoresponsivity of 10⁴A/W and fast response time of about 40 ms. Improvement of photodetection performance is attributed to the balance between light absorption in the perovskite layer and an effective transfer of photogenerated carriers from perovskite entering the MoS₂ channel. This work may provide guidance to develop high-performance hybrid structure optoelectronic devices.