Selective ultrathin gold deposition by organometallic chemical vapor deposition onto organic self-assembled monolayers (SAMs)

We demonstrate a selective deposition of ultrathin gold layers via OMCVD (organometallic chemical vapor deposition) onto self-assembled dithiols. Dithiols have been self-assembled to produce a thiolated surface. The gold layer deposited from a gold precursor, present in the vapor around the sample, is bound to the exposed thiol groups. We demonstrate that it is possible to deposit gold only onto the areas where the binding thiol groups are located, and investigate the growth process with spontaneous desorption time-of-flight mass spectrometry, Rutherford backscattering spectroscopy, atomic absorption spectroscopy and atomic force microscopy.     

Photocatalytic TiO(2) deposition by chemical vapor deposition

Dip-coating, spray-coating or spin-coating methods for crystalline thin film deposition require post-annealing process at high temperature. Since chemical vapor deposition (CVD) process is capable of depositing high-quality thin films without post-annealing process for crystallization, CVD method was employed for the deposition of TiO(2) films on window glass substrates. Post-annealing at high temperature required for other deposition methods causes sodium ion diffusion into TiO(2) film from window glass, resulting in the degradation of photocatalytic efficiency. Anatase-structured TiO(2) thin films were deposited on window glass by CVD, and the photocatalytic dissociation rates of benzene with CVD-grown TiO(2) under UV exposure were characterized. As the TiO(2) film deposition temperature was increased, the (112)-preferred orientations were observed in the film. The (112)-preferred orientation of TiO(2) thin film resulted in a columnar structure with a larger surface area for benzene dissociation. Obviously, benzene dissociation rate was maximum when the degree of the (112) preferential orientation was maximum. It is clear that the thin film TiO(2) should be controlled to exhibit the preferred orientation for the optimum photocatalytic reaction rate. CVD method is an alternative for the deposition of photocatalytic TiO(2).     

Plasmon-assisted chemical vapor deposition

We introduce a new chemical vapor deposition (CVD) process that can be used to selectively deposit materials of many different types. The technique makes use of the plasmon resonance in nanoscale metal structures to produce the local heating necessary to initiate deposition when illuminated by a focused low-power laser. We demonstrate the technique, which we refer to as plasmon-assisted CVD (PACVD), by patterning the spatial deposition of PbO and TiO(2) on glass substrates coated with a dispersion of 23 nm gold particles. The morphology of both oxide deposits is consistent with local laser-induced heating of the gold particles by more than 150 degrees C. We show that temperature changes of this magnitude are consistent with our analysis of the heat-loss mechanisms. The technique is general and can be used to spatially control the deposition of virtually any material for which a CVD process exists.     

Initiated chemical vapor deposition (iCVD) of copolymer thin films

Initiated chemical vapor deposition (iCVD) represents a novel hot-wire CVD variant for producing copolymer thin films. iCVD copolymerization was characterized by a conventional liquid-phase free radical copolymerization equation when applied to methacrylic acid copolymers. FTIR peak shifts with changing comonomer ratios in the copolymers further supported a copolymerization mechanism. Crosslinked methacrylic acid copolymers provided pH-dependent swelling behavior that enabled an enteric release of active core material when the copolymer was used as an encapsulation coating.     

Initiated chemical vapor deposition of poly(2-hydroxyethyl methacrylate) hydrogels

Initiated chemical vapor deposition (iCVD), a low temperature variant of hot-wire chemical vapor deposition (HWCVD) is a solvent-free polymerization technique. It was used to synthesize thick, free-standing films of the hydrogel poly(2-hydroxyethyl methacrylate) (PHEMA). In this work, we show that the iCVD technique can yield PHEMA which is free from residual entrained monomer, has low non-specific protein adsorption and is capable of supporting good cell adhesion and proliferation.     

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     

磁场辅助等离子体增强化学气相沉积

本文根据螺线管线圈内部磁场的分布规律，以及磁场对等离子体内部电子的作用原理，设计了磁场辅助的等离子体增强化学气相沉积（PECVD）系统，并且研究了在PECVD系统中获得均匀磁场的方法。而后，以SiH4和N2为反应气体，在低气压下沉积了SiN薄膜。测量了SiN薄膜的沉积速率，折射率，表面形貌等参数。验证了磁场分布的均匀性，分析了磁场在等离子体增强化学气相沉积系统中的作用。     

Characterization of Al-doped n-type ZnSe prepared under a zinc-rich growth condition by low-pressure organometallic chemical vapor deposition

High conductivity n-type ZnSe with = 0.01 ωcm and n = 2.4 × 10¹⁸ cm⁻³ is obtained on (100) GaAs substrates by low pressure organometallic chemical vapor deposition. The 14 meV full width at half maximum of the 77 K photoluminescence near-band-edge emission shows a high quality of as-grown Al-doped ZnSe epilayers. With a suitable Al doping level, a strong photoluminescence intensity of near-band-edge emission is obtained. The behavior of near-band-edge emission and of self-activated emission related to the incorporation of aluminum are discussed in this paper.     

Large-scale initiated chemical vapor deposition of poly(glycidyl methacrylate) thin films

The initiated chemical vapor deposition (iCVD) of poly(glycidyl methacrylate) (PGMA) was scaled up using dimensionless analysis. In the first stage, PGMA was deposited onto a large stationary substrate and a deposition rate as high as 85 nm/min was achieved. It was found that the deposition rate increases with increasing filament temperature, whereas the deposition rate and the number-average molecular weight decrease with increasing substrate temperature. In the second stage, PGMA was deposited onto a moving substrate. At speeds between 20 mm/min and 60 mm/min, the deposition rate on the moving substrate was found to be equal to the deposition rate on the stationary substrate. Fourier transform infrared spectroscopy showed that the epoxide functionality of the PGMA films was retained during the iCVD process. Since the iCVD polymerization of different vinyl monomers all use similar parameters, this scale up can be applied to the scale up of other vinyl monomers such as 2-hydroxyethyl methacrylate and perfluoroalkyl ethyl methacrylate.     

Metal organic chemical vapor deposition (MOCVD) of oxides and ferroelectric materials

The electrical properties of thin-film oxides span a tremendous range from insulating to superconducting. As a consequence, they are now finding an increasing number of applications in electronics and opto-electronics, both as stand-alone layers and for the provision of added functionality to electronic circuits, especially silicon. The modified precursor delivery technologies (e.g. aerosol or liquid delivery or injection techniques) coupled with improved precursors, and better engineering of the deposition kit, have transformed the prospects for the deposition of these materials by MOCVD. It is now possible to exploit the many traditional advantages of MOCVD, especially over other routes to thin-film oxide deposition. A wide range of oxides and particularly complex ferroelectric oxides are being produced on substrates of up to 200 mm in diameter. This paper highlights the progress and real advantages that MOCVD has for thin-film oxide deposition, including the design of improved precursors. Examples of the deposition of dielectric layers and lead-based ferroelectric layers for uncooled thermal imaging, and MEMS actuation applications are presented.     

Alumina microtubes prepared via template-directed pulsed chemical vapor deposition (pulsed CVD)

Bundles of alumina microtubes were prepared by depositing alumina onto bundles of “endless” carbon fibers via pulsed chemical vapor deposition and subsequent removal of the fibers. Thin alumina films were deposited onto “endless” carbon fibers at 77 °C by gas phase exposures to sequential pulses of trimethylaluminum and water vapor, respectively. The carbon fibers were selectively removed using thermal oxidation in air at temperatures exceeding 550 °C. The length of the tubes was primarily limited by the dimension of the used furnace. The longest tubes thus had a length of 30 cm. Scanning electron microscopic (SEM) images of the microtubes revealed that each individual tube was separated from its neighbors and that the tubes had an almost uniform wall thickness. SEM and transmission electron microscopic (TEM) images indicate that the inner side of the wall has the same morphology as the fiber template. As deposited, the alumina films have a predominantly amorphous structure; this is transformed into a polycrystalline structure during thermal oxidation. At low thermal oxidation temperatures, such as 550 °C, the alumina microtubes still comprise a substantial fraction of amorphous structure, at higher oxidation temperatures, 900 °C or above, a dominating polycrystalline structure (with bigger grains) is formed. This transformation gives rise to grain boundaries. These grain boundaries might facilitate oxygen diffusion and thus oxidative removal of the fiber templates.     

Combinatorial initiated chemical vapor deposition (iCVD) for polymer thin film discovery

Initiated chemical vapor deposition (iCVD) is a technique used to synthesize polymer thin films and coatings from the vapor phase in situ on solid substrates via free-radical mechanisms. It is a solventless, low-temperature process capable of forming very thin conformal layers on complex architectures. By implementing a combinatorial approach that examines five initiation temperatures simultaneously, we have realized at least a five-fold increase in efficiency. The combinatorial films were compared to a series of blanket films deposited over the same conditions to ensure the combinatorial system provided the same information. Direct synthesis from the vapor phase allows for in situ control of film morphology, molecular weight and crosslinking, and the combinatorial system decreases the time required to find the relationship between these interrelated properties. Some coatings were tested for antimicrobial performance against E. coli and B. subtilis.     

催化化学气相沉积法制备螺旋形多壁碳纳米管(英文)

以乙炔为碳源、FeMo/MgO催化剂为模板,采用催化化学沉积法制备了螺旋状多壁碳纳米管(hs-MWC-NTs)。其中FeMo/MgO模板,由作为发泡和助燃剂的柠檬酸燃烧而制成。FeMo/MgO催化剂的XRD谱图揭示其具有微晶的通性。应用SEM、TEM和Raman光谱剖析了合成的炭材料。SEM和TEM观察表明获得了hs-MWC-NTs;Raman光谱的D峰和G峰确认了所获碳纳米管(CNTs)的结晶状态。结果表明:此法乃是合成直径10nm～20nm螺旋形多壁碳纳米管的最容易和简便方法。     

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.     

Hot-wire chemical vapor deposition of carbon nanotubes

Hot-wire chemical vapor deposition (HWCVD) has been employed for the continuous gas-phase generation of both carbon multi-wall and single-wall nanotube (MWNT and SWNT) materials. Graphitic MWNTs were produced at a very high density at a synthesis temperature of 600 °C. SWNTs were deposited at a much lower density on a glass substrate held at 450 °C. SWNTs are typically observed in large bundles that are stabilized by tube–tube van der Waals’ interactions. However, transmission electron microscopy analyses revealed only the presence of isolated SWNTs in these HWCVD-generated materials.     

Rheotaxial diamond growth by chemical vapor deposition

This paper is to report a novel method to synthesize diamond crystal by using a well developed chemical vapor deposition process, but on a liquid substrate, while substrates of prevailing practice are solid. The substrate materials are metals which become liquid at diamond deposition temperature, such as elements Sn and Ga, and eutectic alloys of Cu-Ge, Sn-Ge. One result is that, while reported diamond crystal size was about 10 to 40 micrometers on the solid substrate, on the liquid substrate, the crystal size has reached so far about 300 micrometers. Received: 17 May 2000 / Reviewed and accepted: 8 June 2000     

Initiated chemical vapor deposition of biopassivation coatings

Organosilicon polymers show great utility as both biocompatible and electrically insulating materials. In this work, thin films of a novel organosilicon polymer are synthesized by initiated CVD utilizing trivinyl-trimethyl cyclotrisiloxane as a monomer and terbutyl peroxide as a free radical generating initiator. Use of an initiator allows for formation of polymer films at filament temperatures as low as 250 °C which allows for retention of all siloxane ring moieties within the resulting polymer. The all-dry deposition process generates a highly crosslinked matrix material in which over 95% of the vinyl moieties present on the monomer units have been reacted out to form linear polymerized hydrocarbon chains. The material possesses an electrical resistivity of 4 × 10¹⁵ Ω cm. In addition, biased soak testing of material samples in a simulated biological environment demonstrates retention of electrical material properties for greater than 2 years.     

Plasma-enhanced chemical vapor deposition of nanocrystalline diamond

Nanocrystalline diamond films have attracted considerable attention because they have a low coefficient of friction and a low electron emission threshold voltage. In this paper, the author reviews the plasma-enhanced chemical vapor deposition (PE-CVD) of nanocrystalline diamond and mainly focuses on the growth of nanocrystalline diamond by low-pressure PE-CVD. Nanocrystalline diamond particles of 200–700 nm diameter have been prepared in a 13.56 MHz low-pressure inductively coupled CH₄/CO/H₂ plasma. The bonding state of carbon atoms was investigated by ultraviolet-excited Raman spectroscopy. Electron energy loss spectroscopy identified sp²-bonded carbons around the 20–50 nm subgrains of nanocrystalline diamond particles. Plasma diagnostics using a Langmuir probe and the comparison with plasma simulation are also reviewed. The electron energy distribution functions are discussed by considering different inelastic interaction channels between electrons and heavy particles in a molecular CH₄/H₂ plasma.     

Thick boride coatings by chemical vapor deposition

In this paper we describe an experimental study of the chemical vapor deposition (CVD) of TiB₂ by the hydrogen reduction of TiCl₄ and BCl₃ with the purpose of obtaining very thick (more than 100 μm) and uniform coatings. The optimum deposition conditions were as follows: temperature, 900–950 °C; source gas ratios, $\text{[}\text{Ti}\text{]/[}\text{B}\text{] =}\text{1}\text{2}$ and $\text{[}\text{H}\text{]/[}\text{Cl}\text{] =}\text{6}\text{1}$. With these conditions, deposition rates greater than 25 μm h^-1 were obtained. The composition was very uniform with an excess of boron over stoichiometry (probably in the form of free boron). A small amount of chlorine remained incorporated in the deposit probably as TiCl₂ (0.05 wt.% at 950 °C). The coatings were very hard (about 3700 kgf mm^-2) and hardness was uniform through the thickness. With careful control of the deposition parameters, the CVD of uniform coatings with thickness of 1 mm or more appears feasible.