A facile tool for the characterization of two-dimensional materials grown by chemical vapor deposition

The metrology of two-dimensional (2D) materials such as graphene, boron nitride or molybdenum disulfide grown by chemical vapor deposition (CVD) is critical for the optimization of their synthesis. We demonstrate the use of film-induced frustrated etching (FIFE) as a facile, scalable method to reveal and quantify structural defects in continuous thin sheets. The sensitivity of the analysis technique to intentionally induced lattice defects in graphene compares favorably to the sensitivity of Raman spectroscopy. A strong correlation between the measured defectiveness and the maximum carrier mobility in graphene emphasizes the importance of the technique for growth optimization. Due to its ease and widespread availability, we anticipate that FIFE will find wide application in the characterization of CVD-synthesized 2D materials.      

爆炸辅助气相沉积法制备富勒烯的研究

通过双釜爆炸装置,将爆炸后产生的高温气相碳簇快速转移到温度相对比较低的环境中沉积,成功地制备了C60富勒烯.富勒烯的形成与沉积温度密切相关,当沉积温度为0℃时,紫外光谱以及飞行时间质谱检测表明,产物的甲笨抽提物中生成了C60富勒烯.与其它制备方法相比,本体系的气氛更为复杂,包含H、O、N等元素,此条件下富勒烯的成功制备为深入理解富勒烯的生长机理提供了有用的信息.实验范围内,当沉积温度为450℃、150℃以及-78.5℃时,产物的抽提物中都没有发现富勒烯生成,可能是由于碳簇退火沉积速率太慢或太快造成.     

Synthesis of silicon carbide nanotubes by chemical vapor deposition

Silicon carbide nanotubes (SiCNTs) were directly synthesized by chemical vapor deposition (CVD) in the paper. Methyltrichlorosilane (MTS) was selected as the SiC gaseous source and, ferrocence and thiophene as the catalyst and the cocatalyst, respectively. The influences of reaction temperature, contents of catalyst and cocatalyst, and content of gaseous source on the morphologies of the products were investigated, respectively. The products were identified by high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray (EDX), respectively. The synthesis of SiCNTs by CVD suggested a condition-dependent process. Novel SiCNTs, with 20 approximately 80 nm in outer diameter and 15 approximately 35 nm in inner diameter, respectively, were observed. The wall structure similar to that of carbon nanotubes was not found for the SiCNTs.     

Synthesis of carbon nanowalls by hot-wire chemical vapor deposition

Carbon nanowall (CNW) is a carbon nano-material which has a wall structure that stood on substrates. CNWs can be synthesized by hot-wire chemical vapor deposition (HWCVD) using methane without hydrogen dilution. The synthesis of CNWs by HWCVD is discussed along with reviewing the experimental results. The growth of CNWs is affected by hydrogen dilution ratio and substrate surface temperature. Based on these results, it is suggested that hydrogen radical density and substrate surface temperature are the important parameters for the synthesis of CNWs. The growth process of CNWs is also discussed.     

Synthesis of centimeter-scale WS2 membrane by chemical vapor deposition

Journal of Materials Science: Materials in Electronics - Transition metal dichalcogenides (TMDCs) are among the most widely studied two-dimensional materials due to their unique physical...     

化学气相沉积法制备多壁碳纳米管

以带程序升温装置的管式电阻炉为实验装置,采用化学气相沉积法,在一定的工艺条件下裂解二茂铁与双鸭山精煤的混合物制备出多壁碳纳米管.采用透射电镜、Raman光谱以及X射线衍射技术对碳纳米管产物进行表征,同时研究了碳纳米管的生长机理.     

Synthesis of ZnO hexagonal columnar pins by chemical vapor deposition

Large-quantity of ZnO hexagonal columnar pins are fabricated on a silicon substrate by pyrolysis and oxidation of ZnS powder. We find that each ZnO pin is composed of two parts: a micron-sized hexagonal columnar base, and a tapered hexagonal stalk of 300–500 nm in diameter and 5 μm in length. The entire pin has a hexagonal cross section and grows toward the [0001] direction. Room temperature cathodoluminescence measurement shows that it has a weak near-band edge ultraviolet emission at 383 nm but a strong broad green emission at 527 nm. In sintering, ZnS decomposes to Zn and S. During the growth of these pins, Zn reacts with the incoming O₂ to form ZnO. The growth is governed by the vapor–solid mechanism.     

Synthesis of indium-catalyzed Si nanowires by hot-wire chemical vapor deposition

Indium (In) catalyzed silicon nanowires (SiNWs) were synthesized by using hot-wire chemical vapor deposition (HWCVD) technique. Indium droplets were deposited on Si substrates by hot-wire evaporation of In wire, which was immediately followed by the growth of SiNWs from the droplets. Three sets of samples were prepared by varying the length of In wires, l, as 3, 1 and 0.5 mm. The sizes of In catalyst droplets decreased from 271.4 ± 66.8 to 67.4 ± 16.6 nm when the l was reduced from 3 to 0.5 mm. Larger size of In droplets (271.4 ± 66.8 nm) was found to induce the growth of worm-like NWs. The decrease in size of In catalyst droplets induced the formation of aligned and tapered NWs with smaller tips. The smallest value of tapering parameter, T_p of 40.5 nm/μm is correlated to the SiNWs induced by the smallest size of In droplets (67.4 ± 16.6 nm). The as-grown SiNWs showed high purity and good crystalline structure.     

Tantalum chemical vapor deposition on substrates from various materials

Tantalum coatings have been produced for the first time by hydrogen-free chemical vapor deposition through reduction of tantalum pentabromide with cadmium vapor, which allowed the deposition temperature to be substantially reduced (by more than 200 K). The coatings consisted of α- and/or β-Ta, depending on the substrate material.     

Synthesis of multi-walled carbon nanotubes by microwave plasma-enhanced chemical vapor deposition

Microwave plasma-enhanced chemical vapor deposition (MW-PECVD) has been employed to synthesize carbon nanostructures by using Fe (or Co, Ni)/γ-Al₂O₃ as catalysts and a mixture of benzene, hydrogen, and argon as precursors. By regulating the types of catalyst, the microwave incident power, the ratio and flux of the precursors, many morphologies such as ordinary geometric, helix-shaped, and planar spiral carbon nanotubes with aspect ratios of 100–1000 have been observed. Furthermore, two novel nanostructures, which are probably the missing link between onion-like carbon particles and nanotubes, have also been obtained. The striking feature of this new approach is the low synthesis temperature (<520°C) due to the non-equilibrium characteristic of microwave plasma operated at low pressure, which is crucial for some fascinating applications.     

Synthesis and characterization of Y-shaped carbon fibers by chemical vapor deposition

In this work, Y-shaped carbon fibers with high purity were successfully synthesized by CVD using copper tartrate as a catalyst precursor at low reaction temperature, 279 °C. A model has been proposed for interpreting the mechanism of the Y-shaped carbon fibers growth. It is suggested that the introduction of hydrogen is the key factor to the formation of three carbon fibers growth faces on every the agglomeration of copper monocrystalline catalyst particles and lead to the formation of Y-shaped carbon fibers subsequently. The Y-shaped carbon fibers were characterized by field emission scanning electron microscopy, transmission electron microscopy and X-ray diffraction.     

爆炸辅助气相沉积法合成介孔氮杂碳纳米颗粒

以吡咯作为原料,采用爆炸辅助的化学气相沉积法,成功地合成了氮杂介孔碳纳米颗粒.颗粒尺寸为30～70hm,含有直径为2～4nm的介孔,氮掺杂量为8.81%(at).在此过程中,爆炸反应产生的热能将吡咯分解成碳氮原子簇,这些原子簇在动力学驱动下组装成纳米颗粒.爆炸产生的高能氧化性气体与颗粒上缺陷处的碳原子反应形成孔,体系独特的高温环境有利于对碳纳米颗粒进行有效的结构性氮掺杂,并形成较好的晶化结构.     

化学气相沉积法制备二维Cr_(2)S_(3)纳米片及其磁性研究EI北大核心

以三氯化铬和硫粉为原料,采用常压化学气相沉积法(CVD)成功制备出了二维Cr_(2)S_(3)纳米片,并对Cr_(2)S_(3)纳米片表面形貌、晶体结构、宏观磁性等进行系统研究。结果表明:二维Cr_(2)S_(3)纳米片光学形貌以三角形为主,尺寸最大可达到156.8μm,厚度最小为2.59 nm(约2个单元晶胞厚);晶体结构为菱方相结构,类似于单斜NiAs型晶体结构;磁性测试表明:菱方相的二维Cr_(2)S_(3)低温下呈亚铁磁性,面内为磁易轴方向,其奈尔温度约等于120 K,75 K时饱和磁化强度最大;在空气中放置1个月后二维Cr_(2)S_(3)纳米片依然保持较好的磁性性能,是一种环境稳定的二维磁性材料。     

Near room-temperature ferromagnetism in air-stable two-dimensional Cr1-xTe grown by chemical vapor deposition

Identifying air-stable two-dimensional(2D)ferromagnetism with high Curie temperature(Tc)is highly desirable for its potential applications in next-generation sp...     

热化学气相沉积法在硅纳米丝上合成碳纳米管

利用热化学气相沉积法在负载不同厚度催化剂的硅纳米丝(SiNW)表面生长碳纳米管(CNTs),探讨了生长条件对所合成SiNW-CNT的结构和场发射特性的影响.这种类似树状的三维结构具有较高碳纳米管表面密度及降低的电场筛除效应等潜在优势.使用拉曼光谱( Raman)、电子显微镜(SEM)、透射电子显微镜(TEM)、能量扩散分光仪(EDS)分析了碳纳米管的结构性质,并在高真空下施加电场测得碳纳米管的场发射特性.结果表明:随硅纳米丝上负载催化剂镍膜厚度的变化,所合成碳纳米管的表面特性、结晶结构及功函数改变,导致电子发射难易程度的改变,进一步影响碳纳米管的场发射特性.     

定向碳纳米管的化学气相沉积制备法

报道了一种简便有效的合成定向碳纳米管 (CNTs)的化学气相沉积 (CVD)制备方法。以铁为催化剂 ,乙炔为碳源 ,采用单一反应炉 ,直接在石英基底上沉积催化剂颗粒薄膜 ,成功合成了定向性好、管径均匀的高质量大密度的碳纳米管     

石墨烯的化学气相沉积法制备

化学气相沉积(CVD)法是近年来发展起来的制备石墨烯的新方法,具有产物质量高、生长面积大等优点,逐渐成为制备高质量石墨烯的主要方法.通过简要分析石墨烯的几种主要制备方法(胶带剥离法、化学剥离法、SiC外延生长法和CVD方法)的原理和特点,重点从结构控制、质量提高以及大面积生长等方面评述了CVD法制备石墨烯及其转移技术的研究进展,并展望了未来CVD法制备石墨烯的可能发展方向,如大面积单晶石墨烯、石墨烯带和石墨烯宏观体的制备与无损转移等.     

改进化学气相沉积法在炭纤维表面生长碳纳米管(英文)

采用一种改进的化学气相沉积法在炭纤维表面制备碳纳米管。为了提高炭纤维表面的润湿性能,炭纤维在浸渍之前先在CVD设备中在真空下973 K的高温处理,然后在硝酸和浓硫酸体积比为3∶1的混合酸中酸处理30 min。而改进的化学气相沉积法关键在于让催化剂的还原步骤和碳纳米管的生长步骤同时进行。这样通过减小过渡金属元素与炭纤维之间的接触时间从而降低了它们之间的相互扩散,在确保了炭纤维本身的力学性能下降程度明显小于用普通化学气相法制备的情况下生长出长且茂密的碳纳米管阵列。另外,经过对工艺参数的优化发现当用乙醇作溶剂,Fe(NO3)3.9H2O溶度为100 mmol/L,氢气和碳源气体比值为4/1,而生长时间为30 min时得到最好的碳纳米管阵列。     

Synthesis of silicon carbide nanowires by solid phase source chemical vapor deposition

In this paper, we report a simple approach to synthesize silicon carbide (SiC) nanowires by solid phase source chemical vapor deposition (CVD) at relatively low temperatures. 3C-SiC nanowires covered by an amorphous shell were obtained on a thin film which was first deposited on silicon substrates, and the nanowires are 20–80 nm in diameter and several μm in length, with a growth direction of [200]. The growth of the nanowires agrees well on vapor-liquid-solid (VLS) process and the film deposited on the substrates plays an important role in the formation of nanowires.