Sb2Se3管状化合物的制备和表征

用固相烧结法合成了管状Sb2Se3相变材料,并通过扫描电子显微镜（SEM）、X射线衍射仪（XRD）、透射电镜（TEM）、拉曼光谱仪（Raman）、热重分析（DSC）进行表征测试,结果表明成功制备出了正交晶系的Sb2Se3,计算所得晶格常数为a：11．6445A,b=11．792A,c=3．981A,;透射电镜结果说明Sb2Se3微米管晶体结构沿[001]方向择优生长;DSC测试Sb2Se3的熔点为624．5℃。同时本试验用固相烧结法制备了不同配比的Sb—Se材料,并用XRD和Raman表征测试了晶体结构.     

多元醇法制备和表征Sb2Se3纳米线

以自制的NaHSe乙醇溶液为硒源,在PEG-400无水体系中采用多元醇法,在180℃生长10h制备了直径100～200nm,长度可达十几微米的纳米线.产物通过XRD、TEM、HRTEM、FESEM、EDS和UV-Vis等手段进行了表征,并研究了不同多元醇对产物形貌的影响.研究表明,PEG-400作为结构导向剂在制备一维Sb₂Se₃纳米线中发挥着至关重要的作用,并且无水环境为纳米晶的生长提供了更加纯净的条件,有利于制备高质量的纳米晶.     

Near‐Infrared Photodetectors Based on MoTe2/Graphene Heterostructure with High Responsivity and Flexibility

2D transition metal dichalcogenides (TMDCs) have attracted considerable attention due to their impressively high performance in optoelectronic devices. However, efficient infrared (IR) photodetection has been significantly hampered because the absorption wavelength range of most TMDCs lies in the visible spectrum. In this regard, semiconducting 2D MoTe₂ can be an alternative choice owing to its smaller band gap ≈1 eV from bulk to monolayer and high carrier mobility. Here, a MoTe₂/graphene heterostructure photodetector is demonstrated for efficient near‐infrared (NIR) light detection. The devices achieve a high responsivity of ≈970.82 A W^?1 (at 1064 nm) and broadband photodetection (visible‐1064 nm). Because of the effective photogating effect induced by electrons trapped in the localized states of MoTe₂, the devices demonstrate an extremely high photoconductive gain of 4.69 × 10⁸ and detectivity of 1.55 × 10¹¹ cm Hz^1/2 W^?1. Moreover, flexible devices based on the MoTe₂/graphene heterostructure on flexible substrate also retains a good photodetection ability after thousands of times bending test (1.2% tensile strain), with a high responsivity of ≈60 A W^?1 at 1064 nm at V _DS = 1 V, which provides a promising platform for highly efficient, flexible, and low cost broadband NIR photodetectors.     

Two-Dimensional Palladium Diselenide with Strong In-Plane Optical Anisotropy and High Mobility Grown by Chemical Vapor Deposition

Two-dimensional (2D) palladium diselenide (PdSe₂) has strong interlayer coupling and a puckered pentagonal structure, leading to remarkable layer-dependent electronic structures and highly anisotropic in-plane optical and electronic properties. However, the lack of high-quality, 2D PdSe₂ crystals grown by bottom-up approaches limits the study of their exotic properties and practical applications. In this work, chemical vapor deposition growth of highly crystalline few-layer (≥2 layers) PdSe₂ crystals on various substrates is reported. The high quality of the PdSe₂ crystals is confirmed by low-frequency Raman spectroscopy, scanning transmission electron microscopy, and electrical characterization. In addition, strong in-plane optical anisotropy is demonstrated via polarized Raman spectroscopy and second-harmonic generation maps of the PdSe₂ flakes. A theoretical model based on kinetic Wulff construction theory and density functional theory calculations is developed and described the observed evolution of “square-like” shaped PdSe₂ crystals into rhombus due to the higher nucleation barriers for stable attachment on the (1,1) and (1,−1) edges, which results in their slower growth rates. Few-layer PdSe₂ field-effect transistors reveal tunable ambipolar charge carrier conduction with an electron mobility up to ≈294 cm² V⁻¹ s⁻¹, which is comparable to that of exfoliated PdSe₂, indicating the promise of this anisotropic 2D material for electronics.     

Thermally Phase‐Transformed In2Se3 Nanowires for Highly Sensitive Photodetectors

The photoresponse characteristics of In₂Se₃ nanowire photodetectors with the κ‐phase and α‐phase structures are investigated. The as‐grown κ‐phase In₂Se₃ nanowires by the vapor‐liquid‐solid technique are phase‐transformed to the α‐phase nanowires by thermal annealing. The photoresponse performances of the κ‐phase and α‐phase In₂Se₃ nanowire photodetectors are characterized over a wide range of wavelengths (300–900 nm). The phase of the nanowires is analyzed using a high‐resolution transmission microscopy equipped with energy dispersive X‐ray spectroscopy and X‐ray diffraction. The electrical conductivity and photoresponse characteristics are significantly enhanced in the α‐phase due to smaller bandgap structure compared to the κ‐phase nanowires. The spectral responsivities of the α‐phase devices are 200 times larger than those of the κ‐phase devices. The superior performance of the thermally phase‐transformed In₂Se₃ nanowire devices offers an avenue to develop highly sensitive photodetector applications.     

Improvement of Low‐Temperature zT in a Mg3Sb2–Mg3Bi2 Solid Solution via Mg‐Vapor Annealing

Materials with high zT over a wide temperature range are essential for thermoelectric applications. n‐Type Mg₃Sb₂‐based compounds have been shown to achieve high zT at 700 K, but their performance at low temperatures (<500 K) is compromised due to their highly resistive grain boundaries. Syntheses and optimization processes to mitigate this grain‐boundary effect has been limited due to loss of Mg, which hinders a sample's n‐type dopability. A Mg‐vapor anneal processing step that grows a sample's grain size and preserves its n‐type carrier concentration during annealing is demonstrated. The electrical conductivity and mobility of the samples with large grain size follows a phonon‐scattering‐dominated T^?3/2 trend over a large temperature range, further supporting the conclusion that the temperature‐activated mobility in Mg₃Sb₂‐based materials is caused by resistive grain boundaries. The measured Hall mobility of electrons reaches 170 cm² V^?1 s^?1 in annealed 800 °C sintered Mg_{3 + δ}Sb_1.49Bi_0.5Te_0.01, the highest ever reported for Mg₃Sb₂‐based thermoelectric materials. In particular, a sample with grain size >30 mm has a zT 0.8 at 300 K, which is comparable to commercial thermoelectric materials used at room temperature (n‐type Bi₂Te₃) while reaching zT 1.4 at 700 K, allowing applications over a wider temperature scale.     

Salt-Assisted Low-Temperature Growth of 2D Bi2O2Se with Controlled Thickness for Electronics

Bi₂O₂Se is the most promising 2D material due to its semiconducting feature and high mobility, making it propitious channel material for high-performance electronics that demands highly crystalline Bi₂O₂Se at low-growth temperature. Here, a low-temperature salt-assisted chemical vapor deposition approach for growing single-domain Bi₂O₂Se on a millimeter scale with thicknesses of multilayer to monolayer is presented. Because of the advantage of thickness-dependent growth, systematical scrutiny of layer-dependent Raman spectroscopy of Bi₂O₂Se from monolayer to bulk is investigated, revealing a redshift of the A_1g mode at 162.4 cm⁻¹. Moreover, the long-term environmental stability of ≈2.4 nm thick Bi₂O₂Se is confirmed after exposing the sample for 1.5 years to air. The backgated field effect transistor (FET) based on a few-layered Bi₂O₂Se flake represents decent carrier mobility (≈287 cm² V⁻¹s⁻¹) and an ON/OFF ratio of up to 10⁷. This report indicates a technique to grow large-domain thickness controlled Bi₂O₂Se single crystals for electronics.     

Facile Synthesis of γ‐In2Se3 Nanoflowers toward High Performance Self‐Powered Broadband γ‐In2Se3/Si Heterojunction Photodiode

An effective colloidal process involving the hot‐injection method is developed to synthesize uniform nanoflowers consisting of 2D γ‐In₂Se₃ nanosheets. By exploiting the narrow direct bandgap and high absorption coefficient in the visible light range of In₂Se₃, a high‐quality γ‐In₂Se₃/Si heterojunction photodiode is fabricated. This photodiode shows a high photoresponse under light illumination, short response/recovery times, and long‐term durability. In addition, the γ‐In₂Se₃/Si heterojunction photodiode is self‐powered and displays a broadband spectral response ranging from UV to IR with a high responsivity and detectivity. These excellent performances make the γ‐In₂Se₃/Si heterojunction very interesting as highly efficient photodetectors.     

Chemical Vapor Deposition of High‐Quality and Atomically Layered ReS2

Recently, anisotropic 2D materials, such as black phosphorus and rhenium disulfides (ReS₂), have attracted a lot attention because of their unique applications on electronics and optoelectronics. In this work, the direct growth of high‐quality ReS₂ atomic layers and nanoribbons has been demonstrated by using chemical vapor deposition (CVD) method. A possible growth mechanism is proposed according to the controlled experiments. The CVD ReS₂‐based filed‐effect transistors (FETs) show n‐type semiconducting behavior with a current on/off ratio of ≈10⁶ and a charge carrier mobility of ≈9.3 cm² Vs⁻¹. These results suggested that the quality of CVD grown ReS₂ is comparable to mechanically exfoliated ReS₂, which is also further supported by atomic force microscopy imaging, high‐resolution transmission electron microscopy imaging and thickness‐dependent Raman spectra. The study here indicates that CVD grown ReS₂ may pave the way for the large‐scale fabrication of ReS₂‐based high‐performance optoelectronic devices, such as anisotropic FETs and polarization detection.     

Nanowire‐Seeded Growth of Single‐Crystalline (010) β‐Ga2O3 Nanosheets with High Field‐Effect Electron Mobility and On/Off Current Ratio

2D β‐Ga₂O₃ nanosheets, as fundamental materials, have great potential in next generations of ultraviolet transparent electrodes, high‐temperature gas sensors, solar‐blind photodetectors, and power devices, while their synthesis and growth with high crystalline quality and well‐controlled orientation have not been reported yet. The present study demonstrates how to grow single‐crystalline ultrathin quasi‐hexagonal β‐Ga₂O₃ nanosheets with nanowire seeds and proposes a hierarchy‐oriented growth mechanism. The hierarchy‐oriented growth is initiated by epitaxial growth of a single‐crystalline $(\stackrel{?}{2}01)$β‐Ga₂O₃ nanowire on a GaN nanocrystal and followed by homoepitaxial growth of quasi‐hexagonal (010) β‐Ga₂O₃ nanosheets. The undoped 2D (010) β‐Ga₂O₃ nanosheet field effect transistor has a field‐effect electron mobility of 38 cm² V^?1 s^?1 and an on/off current ratio of 10⁷ with an average subthreshold swing of 150 mV dec^?1. The from‐nanowires‐to‐nanosheets technique paves a novel way to fabricate nanosheets, which has great impact on the field of nanomaterial synthesis and growth and the area of nanoelectronics as well.     

High‐Density Sb2Te3 Nanopillars Arrays by Templated,Bottom‐Up MOCVD Growth

Sb₂Te₃ exhibits several technologically relevant properties, such as high thermoelectric efficiency, topological insulator character, and phase change memory behavior. Improved performances are observed and novel effects are predicted for this and other chalcogenide alloys when synthetized in the form of high‐aspect‐ratio nanostructures. The ability to grow chalcogenide nanowires and nanopillars (NPs) with high crystal quality in a controlled fashion, in terms of their size and position, can boost the realization of novel thermoelectric, spintronic, and memory devices. Here, it is shown that highly dense arrays of ultrascaled Sb₂Te₃ NPs can be grown by metal organic chemical vapor deposition (MOCVD) on patterned substrates. In particular, crystalline Sb₂Te₃ NPs with a diameter of 20 nm and a height of 200 nm are obtained in Au‐functionalized, anodized aluminum oxide (AAO) templates with a pore density of ≈5 × 10¹⁰ cm^?2. Also, MOCVD growth of Sb₂Te₃ can be followed either by mechanical polishing and chemical etching to produce Sb₂Te₃ NPs arrays with planar surfaces or by chemical dissolution of the AAO templates to obtain freestanding Sb₂Te₃ NPs forests. The illustrated growth method can be further scaled to smaller pore sizes and employed for other MOCVD‐grown chalcogenide alloys and patterned substrates.     

2D Inorganic Bimolecular Crystals with Strong In-Plane Anisotropy for Second-Order Nonlinear Optics

2D inorganic bimolecular crystals, consisting of two different inorganic molecules, are expected to possess novel physical and chemical properties due to the synergistic effect of the individual components. However, 2D inorganic bimolecular crystals remain unexploited because of the difficulties in preparation arising from non-typical layered structures and intricate intermolecular interactions. Here, the synthesis of 2D inorganic bimolecular crystal SbI₃·3S₈ nanobelts via a facile vertical microspacing sublimation strategy is reported. The as-synthesized SbI₃·3S₈ nanobelts exhibit strong in-plane anisotropy of phonon vibrations and intramolecular vibrations as well as show anisotropic light absorption with a high dichroism ratio of 3.9. Furthermore, it is revealed that the second harmonic generation intensity of SbI₃·3S₈ nanobelts is highly dependent on the excitation wavelength and crystallographic orientation. This work can inspire the growth of more 2D inorganic bimolecular crystals and excite potential applications for bimolecular optoelectronic devices.     

MOPCVD制备Ti(CN)硬膜研究

采用金属有机物四异丙基钛(Ti［OC     

Dual‐Additive Assisted Chemical Vapor Deposition for the Growth of Mn‐Doped 2D MoS2 with Tunable Electronic Properties

Doping of bulk silicon and III–V materials has paved the foundation of the current semiconductor industry. Controlled doping of 2D semiconductors, which can also be used to tune their bandgap and type of carrier thus changing their electronic, optical, and catalytic properties, remains challenging. Here the substitutional doping of nonlike element dopant (Mn) at the Mo sites of 2D MoS₂ is reported to tune its electronic and catalytic properties. The key for the successful incorporation of Mn into the MoS₂ lattice stems from the development of a new growth technology called dual‐additive chemical vapor deposition. First, the addition of a MnO₂ additive to the MoS₂ growth process reshapes the morphology and increases lateral size of Mn‐doped MoS₂. Second, a NaCl additive helps in promoting the substitutional doping and increases the concentration of Mn dopant to 1.7 at%. Because Mn has more valance electrons than Mo, its doping into MoS₂ shifts the Fermi level toward the conduction band, resulting in improved electrical contact in field effect transistors. Mn doping also increases the hydrogen evolution activity of MoS₂ electrocatalysts. This work provides a growth method for doping nonlike elements into 2D MoS₂ and potentially many other 2D materials to modify their properties.