Synthesis of two-dimensional/one-dimensional heterostructures with tunable width

Two-dimensional/one-dimensional (2D/1D) heterostructures as a new type of heterostructure have been studied for their unusual properties and promising applications in electronic and optoelectronic devices.However,the studies of 2D/1 D het-erostructures are mainly focused on vertical heterostructures,such as MoS2 nanosheet-carbon nanotubes.The research on later-al 2D/1D heterostructures with a tunable width of 1D material is still scarce.In this study,bidirectional flow chemical vapor de-position (CVD) was used to accurately control the width of the WS2/WSe2 (WS2/MoS2) heterostructures by controlling reacting time.WSe2 and MoS2 with different widths were epitaxially grown at the edge of WS2,respectively.Optical microscope,atomic force microscope (AFM),and scanning electron microscope (SEM) images show the morphology and width of the heterostruc-tures.These results show that the width of the heterostructures can be as low as 10 nm by using this method.The interface of the heterostructure is clear and smooth,which is suitable for application.This report offers a new method for the growth of 1D nanowires,and lays the foundation for the future study of the physical and chemical properties of 2D/1D lateral heterostruc-tures.     

Large‐Area Synthesis of Continuous and Uniform MoS2 Monolayer Films on Graphene

Heterostructures composed of multiple layers of different atomically thin materials are of interest due to their unique properties and potential for new device functionality. MoS₂‐graphene heterostructures have shown promise as photodetectors and vertical tunnel transistors. However, progress is limited by the typically micrometer‐scale devices and by the multiple alignments required for fabrication when utilizing mechanically exfoliated material. Here, the synthesis of large‐area, continuous, and uniform MoS₂ monolayers directly on graphene by chemical vapor deposition is reported, resulting in heterostructure samples on the centimeter scale with the possibility for even larger lateral dimensions. Atomic force microscopy, photoluminescence, X‐ray photoelectron, and Raman spectroscopies demonstrate uniform single‐layer growth of stoichiometric MoS₂. The ability to reproducibly generate large‐area heterostructures is highly advantageous for both fundamental investigations and technological applications.     

Recent advances in preparation,properties and device applications of two-dimensional h-BN and its vertical heterostructures

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.     

A large-scale parametric study of InP deposition on patterned substrates

Selective Area Epitaxy (SAE) is the process of locally depositing a semiconductor film on a substrate which has been patterned with an inert masking material such as SiO₂. During deposition by metalorganic chemical vapor deposition (MOCVD), the build up of precursors over the SiO₂ mask causes material to diffuse into the open areas leading to a growth rate increase. SAE is an important technique for electronic and photonic device fabrication, and for the monolithic integration of these devices. The present work is a single comprehensive study, which reports on the impact of all major MOCVD parameters to SAE indium phosphide films. The parameters include pressure, V/III pressure ratio, growth rate, temperature and mask geometry.     

Collective Dipole‐Dominated Doping of Monolayer MoS2: Orientation and Magnitude Control via the Supramolecular Approach

Molecular doping is a powerful, tuneable, and versatile method to modify the electronic properties of 2D transition metal dichalcogenides (TMDCs). While electron transfer is an isotropic process, dipole‐induced doping is a collective phenomenon in which the orientation of the molecular dipoles interfaced to the 2D material is key to modulate and boost this electronic effect, despite it is not yet demonstrated. A novel method toward the molecular functionalization of monolayer MoS₂ relying on the molecular self‐assembly of metal phthalocyanine and the orientation‐controlled coordination chemistry of axial ligands is reported here. It is demonstrated that the subtle variation of position and type of functional groups exposed on the pyridinic ligand, yields a molecular dipole with programed magnitude and orientation which is capable to strongly influence the opto‐electronic properties of monolayer MoS₂. In particular, experimental results revealed that both p‐ and n‐type doping can be achieved by modulating the charge carrier density up to 4.8 10¹² cm^?2. Density functional theory calculations showed that the doping mechanism is primarily resulting from the effect of dipole‐induced doping rather than charge transfer. The strategy to dope TMDCs is a highly modulable and robust, and it enables to enrich the functionality of 2D materials‐based devices for high‐performance applications in optoelectronics.     

Phototransistors with Negative or Ambipolar Photoresponse Based on As‐Grown Heterostructures of Single‐Walled Carbon Nanotube and MoS2

A facile synthesis method for the heterostructures of single‐walled carbon nanotubes (SWCNTs) and few‐layer MoS₂ is reported. The heterostructures are realized by in situ chemical vapor deposition of MoS₂ on individual SWCNTs. Field effect transistors based on the heterostructures display different transfer characteristics depending on the formation of MoS₂ conduction channels along SWCNTs. Under light illumination, negative photoresponse originating from charge transfer from MoS₂ to SWCNT is observed while positive photoresponse is observed in MoS₂ conduction channels, leading to ambipolar photoresponse in devices with both SWCNT and MoS₂ channels. The heterostructure phototransistor, for negative photoresponse, exhibits high responsivity (100–1000 AW^?1) at low bias voltages (0.1 V) in the visible spectrum (500–700 nm) by combining high mobility conduction channel (SWCNT) with efficient light absorber (MoS₂).     

常压化学气相沉积法制备SnO2微纳米材料及其催化发光性质研究

本文利用一种简单的常压化学气相沉积法在氧化石墨烯基底上制备SnO2材料.通过改变沉积参数(氯化亚锡溶液浓度和沉积时间)得到了多种形貌的SnO2微纳米材料.利用SEM,EDS和XPS对其形貌,成分及元素价态进行表征,并对SnO2材料的催化发光性能进行测试.结果表明,以该材料建立的催化发光气体传感器分别对进样2μL的甲醇,乙醇,异丙醇和丙酮展示了较高的灵敏度,快的响应速度及好的重现性.     

The growth of AlInSb by metalorganic chemical vapor deposition

We have grown Al_xIn_1−xSb epitaxial layers by metalorganic chemical vapor deposition using tritertiarybutylaluminum (TTBAl), trimethylindium (TMIn), and triethylantimony (TESb) as sources in a high speed rotating disk reactor. Growth temperatures of 435 to 505°C at 200 Torr were investigated. The V/III ratio was varied from 1.6 to 7.2 and TTBAl/(TTBAl+TMIn) ratios of 0.26 to 0.82 were investigated. Al_xIn_1−xSb compositions from x=0.002 to 0.52 were grown with TTBAl/(TTBAl+TMIn) ratios of 0.62 to 0.82. Under these conditions, no Al was incorporated for TTBAl/(TTBAl+TMIn) ratios less than 0.62. Hall measurements of Al_xIn_1−xSb showed hole concentrations between 5×10¹⁶ cm⁻³ to 2 × 10¹⁷ cm⁻³ and mobilities of 24 to 91 cm²/Vs for not intentionally doped Al_xIn_1−xSb.     

Recent advances in optoelectronic properties and applications of two-dimensional metal chalcogenides

Since two-dimensional (2D) graphene was fabricated successfully, many kinds of graphene-like 2D materials have attracted extensive attention. Among them, the studies of 2D metal chalcogenides have become the focus of intense research due to their unique physical properties and promising applications. Here, we review significant recent advances in optoelectronic properties and applications of 2D metal chalcogenides. This review highlights the recent progress of synthesis, characterization and isolation of single and few layer metal chalcogenides nanosheets. Moreover, we also focus on the recent important progress of electronic, optical properties and optoelectronic devices of 2D metal chalcogenides. Additionally, the theoretical model and understanding on the band structures, optical properties and related physical mechanism are also reviewed. Finally, we give some personal perspectives on potential research problems in the optoelectronic characteristics of 2D metal chalcogenides and related device applications.     

层状二硫化钼纳米薄膜的制备、表征及其超快特性研究

二硫化钼(MoS2)以其可调谐的带隙、较高的调制深度和较宽的吸收波段等优异的光学特性,在超快脉冲激光器领域具有广阔的应用前景。本文采用锂离子-插层法获得了MoS2纳米片溶液,并制备了优良的MoS2纳米薄膜作为可饱和吸收体(SA)。通过X射线衍射仪(XRD)和扫描电子显微镜(SEM)等方法对MoS2纳米薄膜进行了系统的表征分析,结果证明制备所得的MoS2纳米薄膜是少层片状二维结构。随后,将MoS2纳米薄膜作为全固态脉冲激光器的光学器件,放置于长度为85 mm的直线型谐振腔中,得到了1064.5 nm的稳定被动调Q脉冲输出。实验中,当吸收泵浦功率为11.46 W时,获得了最大平均输出功率为216 mW,输出脉宽为300 ns,重复频率为1040 kHz的超短脉冲激光,其单脉冲能量为0.21 μJ,脉冲峰值功率为0.7 mW。     

中红外光学材料的高温性能研究

红外光学材料是红外技术应用的基础之一。适用于3~5μm波段的中波红外光学材料正向高性能、大尺寸、低成本等方面发展,具有广阔的应用前景。介绍了尖晶石陶瓷、蓝宝石晶体和氟化镁多晶等中红外光学材料的基本性质,开展了制备技术、光学性能、力学性能和热学性能的研究,比较了温度对发射率、抗弯强度和热导率的影响。结果表明:尖晶石陶瓷具备较高的发射率;氟化镁多晶抗弯强度较差;蓝宝石晶体综合性能较佳,适用于制备基于高温应用的弧形光学器件。     

金属-碳复合材料的制备及其非线性光学性质研究

基于浸渍法,成功制备了铁含量为10.7 wt％、铜含量为12.9 wt％的金属-碳复合材料,通过扫描电子显微镜、X射线粉末衍射谱、电感耦合等离子体原子发射光谱等手段表征了金属-碳复合材料的结构、形貌、晶型以及元素组成.通过开孔Z扫描实验和光限幅实验对该材料的非线性光学性质进行测试,该材料表现出优秀的反饱和吸收型非线性光...     

Graphene-Based Heterostructure Composite Sensing Materials for Detection of Nitrogen-Containing Harmful Gases

Graphene-based heterostructure composite is a new type of advanced sensing material that includes composites of graphene with noble metals/metal oxides/metal sulfides/polymers and organic ligands. Exerting the synergistic effect of graphene and noble metals/metal oxides/metal sulfides/polymers and organic ligands is a new way to design advanced gas sensors for nitrogen-containing gas species including NH₃ and NO₂ to solve the problems such as poor stability, high working temperature, poor recovery, and poor selectivity. Different fabrication methods of graphene-based heterostructure composite are extensively studied, enabling massive progress in developing chemiresistive-type sensors for detecting the nitrogen-containing gas species. With the components of noble metals/metal oxides/metal sulfides/polymers and organic ligands which are composited with graphene, each material has its attractive and unique electrical properties. Consequently, the corresponding composite formed with graphene has different sensing characteristics. Furthermore, working ambient gas and response type can affect gas-sensitive characteristic parameters of graphene-based heterostructure composite sensing materials. Moreover, it requires particular attention in studying gas sensing mechanism of graphene-based heterostructure composite sensing materials for nitrogen-containing gas species. This review focuses on related scientific issues such as material synthesis methods, sensing performance, and gas sensing mechanism to discuss the technical challenges and several perspectives.     

Effect of deposition temperature on structural,optical properties and configuration of CdSe nanocrystalline thin films deposited by chemical bath deposition

CdSe nanoparticle thin films were deposited on glass substrates by the chemical bath deposition (CBD) method at low deposition temperature ranging from room temperature up to 50 °C while the pH of the bath was kept constant at 12.1. The structural and morphological variation were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) technique. The energy band gap and optical properties were characterized by the absorbance spectra. Rutherford backscattering spectroscopy (RBS) analysis reveals the excess of Cd rather than Se in depth profile along the thin film thickness. The prepared CdSe nanoparticles have cubic structure and by increasing the temperature the deposited films become continues, homogeneous and tightly adherent. The results also revealed that by increasing the deposition temperature from room temperature up to 50 °C, the band gap decreases from 3.52 eV up to 1.84 eV.     

Au/Cd复合电极沉积方法对其与(111)面CdZnTe衬底接触性能的影响

CdZnTe晶片是HgCdTe外延薄膜的理想衬底。为了优化CdZnTe衬底的电学接触性能,作者基于真空蒸发法和磁控溅射法分别在p型导电性CdZnTe晶片(111)B (富碲面)制备Au/Cd复合电极。通过接触粘附试验,研究了复合电极的制备方法对电极与衬底之间的粘附性;利用卢瑟福背散射光谱法（RBS）比较了不同沉积方法下样品的元素深度分布;采用电流-电压(I-V)测试比较了两种制备工艺对Au/Cd复合电极与CdZnTe衬底欧姆接触特性的影响,从而确定了最佳复合电极的制备工艺。     

Microstructure developments and anti-reflection properties of SiO2 films by liquid-phase deposition

In this work, silicon dioxide (SiO₂) films were deposited on a multi-crystalline silicon substrate via liquid-phase deposition (LPD) using hydrofluorosilicic acid (H₂SiF₆) and boric acid (H₃BO₃) aqueous solution. We controlled the surface morphology and grain structure of the film by using the concentration of H₂SiF₆, and the particle sizes were controlled by the concentration of H₃BO₃. Fourier transform infrared spectroscopy showed that three SiO_x peaks exist at 1103, 815, and 463 cm⁻¹, respectively. X-ray diffraction revealed a typical broad peak in the range of 14–55° for the SiO₂ amorphous particles. The refractive index of the LPD film was 1.41. The reflection of the LPD SiO₂ film was affected by the film thickness, and the reflectivity of the film was decreased as the film thickness increased. For the 106 nm SiO₂ film thickness, the average reflectance under the measuring conditions was 14.1%. The low reflectance rendered the film a suitable anti-reflection film in multi-crystalline silicon solar cells.     

Inkjet Printing of MoS2

A simple and efficient inkjet printing technology is developed for molybdenum disulfide (MoS₂), one of the most attractive two‐dimensional layered materials. The technology effectively addresses critical issues associated with normal MoS₂ liquid dispersions (such as incompatible rheology, low concentration, and solvent toxicity), and hence can directly and reliably write uniform patterns of high‐quality (5–7 nm thick) MoS₂ nanosheets at a resolution of tens of micrometers. The technology efficiency facilitates the integration of printed MoS₂ patterns with other components (such as electrodes), and hence allows fabricating various functional devices, including thin film transistors, photoluminescence patterns, and photodetectors, in a simple, massive and cost‐effective manner while retains the unique properties of MoS₂. The technology has great potential in a variety of applications, such as photonics, optoelectronics, sensors, and energy storage.     

脉冲激光沉积法制备ITO薄膜及性质研究

本文采用脉冲激光沉积法(PLD)制备了ITO导电薄膜,并对其形貌、光学性质和电学性质进行了研究.结果表明,使用PLD方法制备的ITO导电薄膜在可见光区的平均透光率约为80%,方块电阻在100～200Ω/□之间.当衬底温度控制在300℃,氧压控制在1.33Pa时,可以得到具有较高透光率和电导率的ITO导电薄膜.     

芳基取代蒽衍生物的合成及发光性能研究

为提高有机电致发光材料热稳定性和发光效率,设计合成了新型萘基蒽类蓝光材料。以9-溴-10-(2-萘基)蒽为原料,分别同4-(1-萘基)苯硼酸和4-(2-萘基)苯硼酸在四(三苯基膦)钯催化下进行Suzuki偶联,合成10-(2-萘基)-9-(4-(1-萘基)苯基)蒽(NPNA-1)和10-(2-萘基)-9-(4-(2-萘基)苯基)蒽(NPNA-2)。采用红外、核磁对其结构进行表征,通过TG、DSC分析对其热稳定性进行研究,采用紫外和荧光光谱对其光谱性能进行表征。在波长378nm波长光激发下,二者均显现出了强发光性能,NAPA-1的λ_(max)为424nm,NAPA-2的λ_(max)为428nm,均为优秀的蓝光材料。     

Novel and Enhanced Optoelectronic Performances of Multilayer MoS2–WS2 Heterostructure Transistors

Van der Waals heterostructures designed by assembling isolated two‐dimensional (2D) crystals have emerged as a new class of artificial materials with interesting and unusual physical properties. Here, the multilayer MoS₂–WS₂ heterostructures with different configurations are reported and their optoelectronic properties are studied. It is shown that the new heterostructured material possesses new functionalities and superior electrical and optoelectronic properties that far exceed the one for their constituents, MoS₂ or WS₂. The vertical transistor exhibits a novel rectifying and bipolar behavior, and can also act as photovoltaic cell and self‐driven photodetector with photo‐switching ratio exceeding 10³. The planar device also exhibits high field‐effect ON/OFF ratio (>10⁵), high electron mobility of 65 cm²/Vs, and high photo­responsivity of 1.42 A/W compared to that in isolated multilayer MoS₂ or WS₂ nanoflake transistors. The results suggest that formation of MoS₂–WS₂ heterostructures could significantly enhance the performance of optoelectronic devices, thus open up possibilities for future nanoelectronic, photovoltaic, and optoelectronic applications.