Sustained and Controlled Release of Volatile Precursors for Chemical Vapor Deposition of Graphene at Atmospheric Pressure

Precursors and catalysts play vital roles in chemical reactions. Considerable efforts have been devoted to the investigation of catalysts for graphene growth by chemical vapor deposition in recent years. However, there has been little research on precursors because of a lack of innovation in term of creating a controllable feeding method. Herein, we present a novel sustained and controlled release approach, and develop a convenient, safe, and potentially scalable feeding system with the assistance of matrix materials and a simple portable feeder. As a result, a highly volatile liquid precursor can be fed accurately to grow large-area, uniform graphene films with optimal properties. This feeding approach will further benefit the synthesis of other two-dimensional materials from various precursors.     

Single-Source Precursors for the Chemical Vapor Deposition of Iron Germanides

Binary iron-germanium phases are promising materials in magnetoelectric, spintronic or data storage applications due to their unique magnetic properties. Previous protocols for preparation of Fe_xGe_y thin films and nanostructures typically involve harsh conditions and are challenging in terms of phase composition and homogeneity. Herein, we report the first example of single source chemical vapor deposition (CVD) of Fe_xGe_y films. The appreciable volatility of [Ge[Fe₂(CO)₈]₂], [Cl₂GeFe(CO)₄]₂ and ^Me₂iPr₂NHC ⋅ GeCl₂ ⋅ Fe(CO)₄ allowed for their application as precursors under standard CVD conditions (^Me₂iPr₂NHC=1,3-diisopropoyl-4,5-dimethylimidazol-2-ylidene). The thermal decomposition products of the precursors were characterized by TGA and powder XRD. Deposition experiments in a cold-wall CVD reactor resulted in dense films of Fe_xGe_y. During the optimization of synthetic conditions for precursor preparation the new iron-germanium cluster Cl₂Ge[Fe₂(CO)₈]Ge[Fe₂(CO)₈] was obtained in experiments with a higher stoichiometric ratio of GeCl₂ ⋅ 1,4-dioxane vs. Fe₂(CO)₉.     

Thermal Plasma Chemical Vapor Deposition of Si-Based Ceramic Coatings from Liquid Precursors

In this paper a process based on the use of rf inductively coupled plasma is applied for the synthesis and deposition of Si-base ceramic materials (i.e., SiC, Si₃N₄, SiO₂). The starting materials are low-cost liquid disilanes. The atomization process is first investigated and the structure of the resulting coatings is characterized by means of X-ray diffraction, scanning electron microscopy as well as with transmission electron microscopy. Results of the influence of some processing parameters (i.e., chamber pressure, spray distance, substrate cooling, plasma gas nature and composition, precursor composition and atomization parameters) on the phase and microstructure of the coating is reported. Control of the microstructure (or nanostructure) as well as the phase content, namely the / ratio of the phases for SiC and Si3N4, can be achieved with such a synthesis and deposition technique.     

Adsorption of Hydrazoic Acid on Pristine Graphyne Sheet: A Computational StudySCI北大核心CSCD

Herein we have investigated the interaction between hydrazoic acid(HN3) and a pristine graphyne system based on density functional theory(DFT) method using generalized gradient approximation. The van der Waals dispersion correction is also considered for predicting the possibility of using the graphyne system for detection of hydrazoic acid. Pristine graphyne has a band gap of 0.453 eV, which decreases to 0.424 eV when HN3 is adsorbed on graphyne. The electrical conductivity of HN3-adsorbed graphyne is greater than that of its pristine counterpart. Charge transfer analysis reveals that the HN3-adsorbed graphyne system behaves as an n-type semiconductor; however, its pristine analogue acts as an intrinsic semiconductor. Pristine graphyne has zero dipole moment; however, its interaction with HN3 increases its dipole moment. The electronic properties of graphyne is significantly influenced by the presence of HN3, leading to the possibility of designing graphyne-based sensors for HN3 detection.     

Initiated Chemical Vapor Deposition of Poly(furfuryl methacrylate)

Furan ring‐functionalized solid surfaces are achieved by the initiated chemical vapor deposition (iCVD) method, a solvent‐free process to form films under mild conditions. The polymerization of furfuryl methacrylate monomer is initiated by a resistively heated filament wire. The functionality of the furan group in the iCVD film enabled Diels–Alder chemistry with 4‐phenyl‐1,2,3‐triazolin‐3,5‐dione (N‐PTD).

     

Nanostructured ZrO2 and Zr‐C‐N Coatings from Chemical Vapor Deposition of Metal‐Organic Precursors

Nanocrystalline zirconium carbonitride (Zr‐C‐N) and zirconium oxide (ZrO₂) films were deposited by chemical vapor deposition (CVD) of zirconium‐tetrakis‐diethylamide (Zr(NEt₂)₄) and ‐tert‐butyloxide (Zr(OBu^t)₄), respectively. The films were deposited on iron substrates and characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS). The Zr‐C‐N films show blue, golden brown or bronze colours, with colour stability depending upon the precursor composition (pure metal amide or mixed with Et₂NH). The deposition temperature showed no pronounced effect on the granular morphology of the Zr‐C‐N films. The XRD data of the films correspond to the formation of carbonitride phase whereas the XPS analyses revealed a strong surface oxidation and incorporation of oxygen in the film. The films deposited using a mixture of Zr(NEt₂)₄ and Et₂NH showed higher N content, better adhesion and scratch resistance when compared to films obtained from the CVD of pure Zr(NEt₂)₄. Subject to the precursor composition and deposition temperature (550‐750 °C), the microhardness values of Zr‐C‐N films were found to be in the range 2.11‐5.65 GPa. For ZrO₂ films, morphology and phase composition strongly depend on the deposition temperature. The CVD deposits obtained at 350 °C show tetragonal ZrO₂ to be the only crystalline phase. Upon increasing the deposition temperature to 450 °C, a mixture of tetragonal and monoclinic modifications was formed with morphology made up of interwoven elongated grains. At higher temperatures (550 and 650 °C), pure monoclinic phase was obtained with facetted grains and developed texture.     

Superclean Growth of Graphene Using a Cold-Wall Chemical Vapor Deposition Approach

Chemical vapor deposition (CVD) has become a promising approach for the industrial production of graphene films with appealing controllability and uniformity. However, in the conventional hot-wall CVD system, CVD-derived graphene films suffer from surface contamination originating from the gas-phase reaction during the high-temperature growth. Shown here is that the cold-wall CVD system is capable of suppressing the gas-phase reaction, and achieves the superclean growth of graphene films in a controllable manner. The as-received superclean graphene film, exhibiting improved optical and electrical properties, was proven to be an ideal candidate material used as transparent electrodes and substrate for epitaxial growth. This study provides a new promising choice for industrial production of high-quality graphene films, and the finding about the engineering of the gas-phase reaction, which is usually overlooked, will be instructive for future research on CVD growth of graphene.     

Microstructure and Chemical Bonding in Silicon Carbonitride Films Synthesized by Plasma Enhanced Chemical Vapor Deposition

Silicon carbonitride films were synthesized by plasma enhanced chemical vapor deposition using silyl derivatives of asymmetric dimethylhydrazine, (CH₃)₂HSiNHN(CH₃)₂ and (CH₃)₂Si[NHN(CH₃)₂]₂, as molecular precursors. The film material consists of an amorphous matrix with nanocrystalline inclusions. Indexing of synchrotron radiation Xray diffraction patterns suggests that the structure of the nanocrystals is tetragonal with lattice parameters a = 9.6 and c = 6.4. Xray photoelectron spectra indicate that Si—N and C—N sp ³ hybrid bonds are predominant. The absence of G or Dmodes in Raman spectra, which are otherwise typical of structures possessing sp ² bonding, provides further support for the tetragonal structure of the nanocrystals.     

Molecular Design of Fluorocarbon Film Architecture by Pulsed Plasma Enhanced and Pyrolytic Chemical Vapor Deposition

Pulsed plasma enhanced chemical vapor deposition (pulsed PECVD) and pyrolytic chemical vapor deposition (pyrolyric CVD) of fluorocarbon films from hexafluoropropylene oxide (HFPO) have demonstrated the ability to molecularly design film architecture. Film structures ranging from highly amorphous crosslinked matrices to linear perfluoroalkyl chain crystallites can be established by reducing the modulation frequency of plasma discharge in plasma activated deposition and by eventually shifting mechanistically from an electrically activated to a thermally activated process. X-ray photoelectron spectroscopy (XPS) showed CF₂ content increasing from 39–65 mol%. Fourier transform infrared spectroscopy (FTIR) showed an increasing resolution between the symmetric and asymmetric CF₂ stretches, and a reduction in the intensity of the amorphous PTFE and CF₃ bands. High-resolution solid-state ¹⁹F nuclear magnetic resonance spectroscopy (NMR) revealed an increasing CF₂CF₂CF₂ character, with the pyrolytic CVD film much like bulk poly(tetrafluoroethylene) (PTFE). X-ray diffraction (XRD) patterns evidenced an increase in crystallinity, with the pyrolytic CVD film showing a characteristic peak at 2 = 18° representing the (100) plane of the hexagonal structure of crystalline PTFE above 19°C.     

微波等离子体化学气相沉积法低温合成纳米碳管

纳米碳管的低温合成是纳米碳管合成的一个重要研究方向。在众多的合成方法 中,化学气相沉积法,特别是等离子体化学气相沉积法在纳米碳管的低温合成方面 意义重大。本研究利用溶胶-凝胶法结合等离子体还原,获得了负载在SiO_2上的纳 米金属钻颗粒。以甲烷为碳源、氢气为载气,在纳米金属钴颗粒的催化作用下,利 用微波等离子体化学气相沉积法在低于500 ℃ 的温度条件下合成了纯度较高的纳 米碳管。     

Plasma Enhanced Chemical Vapor Deposition of Fluorinated Amorphous Carbon Thin Films from Tetrafluoroethylene and Tetraisocyanatesilane

Fluorinated amorphous carbon films were prepared from tetrafluoroethylene (TFE; C₂F₄) and tetraisocyanatesilane (TICS; Si(NCO)₄) using an RF plasma enhanced chemical vapor deposition method for the purpose of application to inter layer low permittivity films used in large scale integrated circuits. Structure of the deposited films was investigated by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Adhesion characteristics were examined by a tape-peel method. Permittivity of the films was investigated from capacitance measurement on metal-insulator-semiconductor structure. The structural analysis revealed that the deposited films contained imide-like group in spite of the fact that TICS molecules contained isocyanate group . The films deposited under the flow ratio TICS/(TFE + TICS) = 70% showed permittivity of 2.3, good adhesion on silicon substrates, and higher thermal stability than the films deposited without TICS.     

类石墨烯二硫化钨薄膜的化学气相沉积法制备及其应用

类石墨烯过渡金属硫属化合物如MoS₂、WS₂、MoSe₂、WSe₂等因为具有层数依赖的带隙结构而受到了广泛关注。尤其是本征态的WS₂为双极性半导体,它同时具有n型和p型电输运特性,有望在电子电路、存储器件、光电探测和光伏器件方面得以广泛应用。近年来,化学气相沉积技术已经被广泛用于制备大面积二维硫属化合物(如MoS₂, MoSe₂, WS₂ 和WSe₂)原子层薄膜。目前关于其他二维材料体系的综述文献介绍较多,但是针对WS₂介绍的综述文献还鲜有报道。因此,本文综述了类石墨烯WS₂薄膜的化学气相沉积法制备和相关器件的国内外研究进展,讨论了WS₂薄膜的化学气相沉积法制备机理及生长因素如硫粉含量、载气的成分、反应温度、基底材料等对薄膜成膜质量的影响,介绍了WS₂薄膜在晶体管、光电器件及与其他二维材料构成的异质结构器件的最新研究成果,并对可能存在的问题进行了分析和述评。     

Atomic Hydrogen Induced Chemical Vapor Deposition of Silicon Oxycarbide Thin Films Derived from Diethoxymethylsilane Precursor

Amorphous silicon oxycarbide (a-SiOC:H) films produced by remote plasma RPCVD from diethoxymethylsilane (DEMS) were characterized in terms of their basic properties related to the coatings deposited using conventional plasma enhanced PECVD method. The effect of substrate temperature (T_S) on the growth rate, chemical composition, structure, and properties of resulting a-SiOC:H films is reported. Film growth is an adsorption-controlled process, wherein two mechanisms can be distinguished with a transition at about T_S=70°C. Depending on the temperature, films of different nature can be obtained, from polymer-like to highly crosslinked material with C-Si-O network. The chemical structure of a-SiOC:H films was characterized by FTIR, ¹³C and ²⁹Si solid-state NMR, and X-ray photoelectron spectroscopes. The a-SiOC:H films were also characterized in terms of their density, refractive index, surface morphology, conformality of coverage, hardness, adhesion to a substrate, and friction coefficient. The films were found to be morphologically homogeneous materials exhibiting good conformality of coverage and small surface roughness. Their refractive index exhibits anomalous effect revealing a minimum value at T_S=125°C. Due to their exceptional physical properties a-SiOC:H films produced by RPCVD from DEMS precursor seems to be useful as potential dielectric materials or coatings for various encapsulation applications.     

Superclean Growth of Graphene Using a Cold‐Wall Chemical Vapor Deposition Approach

Chemical vapor deposition (CVD) has become a promising approach for the industrial production of graphene films with appealing controllability and uniformity. However, in the conventional hot‐wall CVD system, CVD‐derived graphene films suffer from surface contamination originating from the gas‐phase reaction during the high‐temperature growth. Shown here is that the cold‐wall CVD system is capable of suppressing the gas‐phase reaction, and achieves the superclean growth of graphene films in a controllable manner. The as‐received superclean graphene film, exhibiting improved optical and electrical properties, was proven to be an ideal candidate material used as transparent electrodes and substrate for epitaxial growth. This study provides a new promising choice for industrial production of high‐quality graphene films, and the finding about the engineering of the gas‐phase reaction, which is usually overlooked, will be instructive for future research on CVD growth of graphene.     

Initiated Chemical Vapor Deposition and Light‐Responsive Cross‐Linking of Poly(vinyl cinnamate) Thin Films

The first vapor‐phase deposition of poly(vinyl cinnamate) (PVCin) is reported. Initiated chemical vapor deposition (iCVD) is used to synthesize PVCin thin films with an average thickness of 100 nm. Free radical polymerization and cyclization reactions compete during the deposition process, with approximately 45% of the repeat units undergoing cyclization. Exposure to UV light (λ = 254 nm) induces dimerization (cross‐linking) of the PVCin, which is quantified using spectroscopic techniques. Approximately 90% of the free cinnamate moieties are dimerized at a UV dose of 300 mJ cm⁻². PVCin is also incorporated into a copolymer with N‐isopropylacrylamide, which exhibits a characteristic change in hydrophilicity with temperature. The copolymer is selectively cross‐linked through a mask, and reversible swelling of patterns with 30 μm resolution is demonstrated by submerging the film in water.

     

化学气相沉积法制备Sn2S3一维纳米结构阵列

运用化学气相沉积法(CVD), 直接以Sn和S为原料分区加热蒸发, 通过控制温度分布、气压、载气流量和金属铅纳米颗粒分布等宏观实验条件, 成功制备大面积Sn₂S₃一维纳米结构阵列. 扫描电子显微镜(SEM)图片显示: Sn₂S₃一维纳米结构的横向尺度在100 nm左右, 长约几个微米. X射线衍射（XRD）谱显示: 所制备样品的晶体结构属于正交晶系, 沿[002]方向生长. 紫外-可见漫反射谱表明Sn₂S₃一维纳米结构是带隙为2.0 eV的直接带隙半导体. 讨论了温度分布和金属铅纳米颗粒对Sn₂S₃一维纳米结构生长的影响, 并指出其生长可能遵循气-固(V-S)生长机理.     

以甲苯为前驱体化学液气相沉积法制备碳/碳复合材料

以甲苯为前驱体利用化学液气相沉积法,采用碳布叠层作预制体,于950℃下沉积9h制备了密度为1.63g/cm³的碳/碳复合材料.用金相显微镜、扫描电子显微镜(SEM)和X射线粉末衍射(XRD)等手段对所得的材料进行了组织结构分析,并测定了其力学性能.实验结果表明,以甲苯为前驱体利用该方法可以制备组织结构比较均匀的碳/碳复合材料.用GC/MS气相色谱质谱联用仪对甲苯热分解产物(不挥发成分)进行了成分分析,提出了甲苯裂解制备碳/碳复合材料的初期热裂解机理和热缩聚机理.     

An Investigation into the Optimum Thickness of Titanium Dioxide Thin Films Synthesized by Using Atmospheric Pressure Chemical Vapour Deposition for Use in Photocatalytic Water Oxidation

Twenty eight films of titanium dioxide of varying thickness were synthesised by using atmospheric pressure chemical vapour deposition (CVD) of titanium(IV) chloride and ethyl acetate onto glass and titanium substrates. Fixed reaction conditions at a substrate temperature of 660 °C were used for all depositions, with varying deposition times of 5–60 seconds used to control the thickness of the samples. A sacrificial electron acceptor system composed of alkaline sodium persulfate was used to determine the rate at which these films could photo‐oxidise water in the presence of 365 nm light. The results of this work showed that the optimum thickness for CVD films on titanium substrates for the purposes of water oxidation was ≈200 nm, and that a platinum coating on the reverse of such samples leads to a five‐fold increase in the observed rate of water oxidation.     

硫化锌与硫化锌/氧化锌异质结纳米线的化学气相沉积法制备与表征

介绍一种利用石墨还原快速制备大量硫化锌纳米线的方法,并分别合成了超晶格型、双轴型、核/壳型的硫化锌/氧化锌异质结纳米线。所合成的硫化锌纳米线存在六方纤锌矿和立方闪锌矿两种晶型,纳米线长度达几十微米,直径在20-50 nm,直径均匀且产量很高。在具有双轴型的硫化锌/氧化锌异质结中,首次发现具有超结构特征的氧化锌。HRTEM分析表明,硫化锌/氧化锌超晶格异质结界面为ZB-ZnS(111)∥ZnO(0001),而核/壳型异质结界面为W-ZnS(0001)∥ZnO(0001),这三个晶面分别为各自晶体的极性面,即所合成的硫化锌/氧化锌异质结中极性面相互平行。对ZnS 和ZnS/ZnO 异质结的生长机制进行了探讨,并对硫化锌纳米线与硫化锌/氧化锌异质结的光学性质进行了分析。