Chemical Vapor Deposition最新文献

The atomic layer deposition (ALD) of Gd₂O₃ from tris(isopropyl-cyclopentadienyl) gadolinium (Gd(ⁱPrCp)₃) and O₃ is studied as a function of the O₂/N₂ ratio used to generate O₃. ALD using O₃ with low N₂ content leads to the formation of a hydroxyl-terminated surface after combustion reactions during O₃ exposure followed by proton transfer and ligand release during the Gd(ⁱPrCp)₃ half cycle. This condition leads to the presence of parasitic chemical vapor deposition (CVD) due to the hygroscopicity of Gd₂O₃. By contrast, long O₃ pulses with high N₂ content lead to the dehydroxylation of the surface and to the suppression of both the proton transfer during the Gd(ⁱPrCp)₃ half cycle as well as the parasitic CVD reactions.

The growth of vanadium dioxide is carried out using chemical vapor deposition with N₂ flow rates of 1, 1.4 and 2.2 L min⁻¹ through the vanadium precursor bubbler. The presence of both monoclinic and metastable vanadium dioxide phases with the co-existence of nanocrystallites and outgrowths on the coating surface is observed for the 1 L min⁻¹. Additionally, the electrochemical performance for this sample is enhanced and the specific discharge capacity was the highest presenting capacitance retention of 97% after 500 scans. Finally, it is found that the diffusion of Li⁺ through the cathode/electrolyte interface is easier enhancing its capacitive performance.

Macroporous inorganic structures with high surface-to-volume ratio have been recognized as a centre of interest in many fields. Here, attention is focused on a hybrid synergic methodology to prepare honey-comb (HC) anatase TiO₂ films with increased specific surface area. The breath figures (BFs) method is exploited to produce HC polystyrene (PS) templates and atomic layer deposition (ALD) is used to conformally cover them with a TiO₂ coating. Different approaches are tested to preserve the HC-TiO₂ structure during the conversion of the hybrid organic/inorganic materials into crystalline anatase films. Best results are obtained operating with ALD at 180 °C on pre-UV cross-linked substrates.

We present the direct liquid injection CVD of aluminum oxide and oxycarbide thin films using dimethylaluminum isopropoxide at high process temperature (500–700 °C) with the addition of O₂ gas, and at low temperature (150–300 °C) with the addition of H₂O vapor. Very smooth films with typical roughness values lower than 2 nm are obtained. The thin films are composed of an amorphous material. The composition evolves as a function of temperature from that of a partial hydroxide to a stoichiometric oxide at low deposition temperature (150–300 °C), and from that of a stoichiometric oxide to a mixture of an oxide with an (oxy) carbide at higher temperature (500–700 °C).

There has been a resurgence of interest in metal carbodiimides in recent years and in this paper we present a route to the synthesis of one of these phases, zinc carbodiimide, previously known as zinc cyanamide, in the form of a sub-micrometer thin film, using aerosol-assisted (AA)CVD from a solution of zinc acetate and urea in methanol, with the carbodiimide ion being formed from the decomposition of the urea molecule. Thin film synthesis is achieved over a deposition temperature range 375 − 500 °C, with a minimum ratio of urea to zinc acetate of 2:1 and a maximum of 5:1 established as viable for film formation. This work presents the first example of the synthesis of a ZnNCN thin film, or indeed any metal carbodiimide thin film, using a CVD technique.

Plasma polymers are often limited by their susceptibility to spontaneous and photo-oxidation. We show that the unusual photoluminescence (PL) behavior of a plasma polymer of trans-2-butene is correlated with its PL strength. These photo-processes occur under blue light illumination (λ = 405 nm), distinguishing them from traditional ultraviolet degradation of polymers. These photo-active defects are likely formed during the plasma deposition process, and we show that a polymer synthesized using initiated (i)CVD, a non-plasma method, has 1000× lower PL signal and enhanced photo-stability. Non-plasma methods, such as iCVD, may therefore be a route to overcoming material aging issues that limit the adoption of plasma polymers.

The synthesis of poly(2,2,3,4,4,4-hexafluorobutyl acrylate) (PHFBA) thin films using plasma enhanced chemical vapor deposition (PECVD) method is reported. PHFBA is a non-toxic and low surface energy polymer containing a –CF₃ end group, which makes PHFBA a suitable hydrophobic finish. The effects of plasma power and substrate temperature on chemical and morphological structure of as-deposited films are studied. A greater retention of the perfluoroalkyl functionality is found for the depositions carried out at low powers and high temperatures. PHFBA thin films show superhydrophobic properties when deposited on rough fiber mat surfaces with observed water contact angles greater than 150 degrees.

High flexible SiC nanowires with diameters in the range of 10 to 50 nm and lengths of several hundred micrometers to several millimeters are synthesized using a novel catalyst-assisted fluidized bed chemical vapor deposition method. Methyltrichlorosilane (MTS) is used as source material and particles containing cobalt were used as catalyst. The fluidized bed is specially designed to form a perpendicular uneven temperature distribution. Suspended nanosized liquid catalyst droplets are produced at middle high temperature zone and SiC nanowires are formed in situ on the catalyst droplets then accumulated at the upper part of fluidized bed. The nanowires exhibit a single crystal feature with some stacking faults. Transmission electron microscopy (TEM) analysis verifies a growth direction along the <111> axis of the nanowires. A blue shift optical emission band at about 420 nm is detected using photoluminescence spectroscopy. From the high-resolution TEM investigation, a nanoscale smooth plane between the nanowire and the catalyst tip is observed and the two phases exhibit highly epitaxial growth interface. The growth process of the nanowires is discussed and a possible formation mechanism is proposed.