Combustion Chemical Vapor Deposition Process Research Articles

Facile fabrication of microlenses with controlled geometrical characteristics by inkjet printing on nanostructured surfaces prepared by combustion chemical vapour deposition

Precise positioning of microlenses with well-defined optical characteristics is key in the further development of CCD cameras, biosensors or optical fiber interconnects. Inkjet printing enables accurate microfabrication of microlenses however inks generally employed for this purpose contain solvents that need to be evaporated before the lens solidification process. Besides, the receiving substrate needs to be conditioned, sometimes using complex photolithographic steps to lead to large contact angles of the deposited ink drop that are needed to attain large numerical aperture microlenses. This paper describes the fabrication of microlenses with controlled geometrical characteristics by inkjet printing a solvent-free photocurable formulation. The employed photoacid catalyzed organic–inorganic hybrid ink can be cured just after deposition, without any intermediate evaporation or annealing step, enormously simplifying microlens fabrication process. Besides, a simple combustion chemical vapour deposition process, leading to a porous layer with nano-roughness, followed by a silanization step using a fluorosilane enables the generation of a surface that provides access to a large range of contact angles for the ink drops that are printed on this surface. Single droplet microball lenses with contact angles up to 115°, beyond the hemispherical microlenses, are demonstrated with this industrially viable, cost-effective and high-throughput method.

Cobalt and manganese carboxylates for metal oxide thin film deposition by applying the atmospheric pressure combustion chemical vapour deposition process.

Coordination complexes [M(O2CCH2OC2H4OMe)2] (M = Co, 4; M = Mn, 5) are accessible by the anion exchange reaction between the corresponding metal acetates [M(OAc)2(H2O)4] (M = Co, 1; M = Mn, 2) and the carboxylic acid HO2CCH2OC2H4OMe (3). IR spectroscopy confirms the chelating or μ-bridging binding mode of the carboxylato ligands to M(ii). The molecular structure of 5 in the solid state confirms a distorted octahedral arrangement at Mn(ii), setup by the two carboxylato ligands including their α-ether oxygen atoms, resulting in an overall two-dimensional coordination network. The thermal decomposition behavior of 4 and 5 was studied by TG-MS, revealing that decarboxylation occurs initially giving [M(CH2OC2H4OMe)2], which further decomposes by M–C, C–O and C–C bond cleavages. Complexes 4 and 5 were used as CCVD (combustion chemical vapour deposition) precursors for the deposition of Co3O4, crystalline Mn3O4 and amorphous Mn2O3 thin films on silicon and glass substrates. The deposition experiments were carried out using three different precursor solutions (0.4, 0.6 and 0.8 M) at 400 °C. Depending on the precursor concentration, particulated layers were obtained as evidenced by SEM. The layer thicknesses range from 32 to 170 nm. The rms roughness of the respective films was determined by AFM, displaying that the higher the precursor concentration, the rougher the Co3O4 surface is (17.4–43.8 nm), while the manganese oxide films are almost similar (6.2–9.8 nm).

Laser-assisted vibrational control of precursor molecules in diamond synthesis

Control of chemical reactions is the essence of chemistry, producing designed outcomes while suppressing unwanted side products. Laser-assisted molecular vibrational control has been demonstrated to be a potential approach to influencing the outcome of a chemical reaction. In this article, we reviewed recent progress in the laser control of diamond synthesis through vibrational excitation of precursor molecules in a laser-assisted combustion chemical vapor deposition process. Significantly promoted diamond deposition rate (139μm/h) and crystalline quality were achieved by resonantly exciting the Q-branch (ΔJ=0) of the CH2-wagging mode (v7 mode 949.3cm−1) of C2H4 molecules. Resonant excitation of the fundamental vibrational modes is more effective in promoting diamond growth than random vibrational excitation. Control of diamond crystallographic orientation was also realized by resonantly exciting the R branch (ΔJ=1) of the CH2-wagging mode of C2H4 molecules and resulted in the preferential growth of {100}-oriented diamond crystals. Nitrogen-doped diamond films with a nitrogen concentration of 1.5×1020atoms/cm3 were synthesized by resonantly exciting the rotational–vibrational transition (J=5→J′=6, K=0) of the N–H wagging mode (v2 mode) in ammonia molecules. The findings demonstrate the feasibility of laser-assisted vibrational control in steering chemical reactions and controlling reaction outcomes.

Conductive zinc oxide thin film coatings by combustion chemical vapour deposition at atmospheric pressure

We have established a combustion chemical vapour deposition (C-CVD) system for the deposition of zinc oxide (ZnO) at atmospheric pressure. This C-CVD process has the advantage of a short exposure of the substrates to the flame. It is also potentially applicable as an inline coating system.Fundamental studies were performed on undoped ZnO. The specific resistivity of these layers strongly depends on the film thickness and decreases with increasing thickness. As the lowest resistivities, values of about 2.0·10−1Ωcm are achieved. Ultra-violet photoemission spectra show the valence band structure of the deposited ZnO. The work function and valence band edge were determined. UV–vis spectra were taken to investigate the transmission of the coated glass samples. From these spectra the band gap energy was obtained. Raman spectroscopy as well as infrared spectroscopy confirmed the presence of ordered ZnO crystallites. The X-ray diffraction verified this result and illustrates the hexagonal structure. In the mid-infrared range precursor deposits were detected for low substrate temperatures.

Thin functional films by combustion chemical vapour deposition (C-CVD)

The use of the atmospheric pressure C-CVD (combustion chemical vapour deposition) process for the deposition of thin functional layers on float glass and plastics is described. We will give an overview on the variety of materials that can be deposited and some examples, like SiO2, WOx and Ag, are presented in more detail with potential applications.

The use of silver(I)-2-[2-(2-methoxyethoxy)ethoxy]acetate as precursor in the deposition of thin silver layers on float glass by the atmospheric pressure combustion chemical vapor deposition process

The innovative use of silver(I)-2-[2-(2-methoxyethoxy)ethoxy]acetate ([AgO 2C(CH 2OCH 2) 3H], 3) as precursor for the deposition of silver on float glass by applying the atmospheric pressure combustion chemical vapor deposition process is described. As nucleation layer tungsten oxide was utilized, conformal, closed and dense silver layers of ca. 70 nm thickness were obtained. They are adhesive and high reflective with a resistivity of 5 ∙ 10 − 8 Ωm.

Ferroelectric Phase Shifters at 20 and 30 GHz

This paper presents continuously variable 20- and 30-GHz ferroelectric 360deg phase shifters. A lumped-element all-pass network topology is used for the phase-shifter designs. The phase shifters are fabricated using barium-strontium-titanate (BST) capacitors as the tuning element. The BST thin films are epitaxially grown on sapphire substrates using the combustion chemical vapor deposition process, exhibiting low loss and high tunability. The 20-GHz phase shifter has a dimension of 0.95times1.32times0.5 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ; its maximum phase shift occurs at 21.7 GHz, where the insertion loss varies from 6.1 to 3.9 dB and the return loss is from 15.2 to 4.7 dB. Measured figure-of-merit is 54deg/dB using the highest insertion loss. The dimension of the 30-GHz phase shifter is 1times1.2times0.5 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3 </sup> . Measured insertion loss and return loss vary from 7.0 to 4.3 dB and from 29 to 4.8 dB, respectively, at a center frequency of 32 GHz. The figure-of-merit is 51deg/dB. The dc bias required to tune the low-voltage phase shifters is 0-30 V. Typical third-order input intercept power (IIP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) of the phase shifters is greater than 30 dBm

Luminescence properties of Mn 2+ doped Zn 2SiO 4 phosphor films synthesized by combustion CVD

Zn 2SiO 4:Mn 2+ phosphor films were successfully prepared by a novel combustion chemical vapor deposition (CCVD) method. In the CCVD process, a flammable solution, containing precursor materials, is atomized and sprayed through a specially designed nozzle and ignited to form a combustion flame. This enables crystallized films to be directly deposited onto a substrate in open-atmosphere with no post deposition heat treatment. SEM images indicated that the film deposited at 1200 °C consisted of densely packed particles with a fine grain size of several 100 nm. Strong Photoluminescence (PL) and cathodoluminescence (CL) intensities were observed with Zn 2SiO 4:Mn 2+ samples deposited at a substrate temperature of 1200 °C exhibiting the best crystallinity and highest luminescence. The optimum doping level for films deposited using CCVD was found to be ∼4 mol% Mn 2+ of starting concentration, with a maximum CL luminescence equivalent to 53% of the luminescence measured from a commercial powder phosphor. A relatively fast CL decay with life time about 0.6–0.7 ms was also observed from these films.

Porous SOFC Anodes Prepared by Sublimation of an Immiscible Metal Oxide during Sintering

Nanostructured composite powder, consisting of 20 wt % SnO 2 , 50 wt % NiO, and 30 wt % Gd 0.1 Ce 0.9 O 2 (GDC), was prepared using a combustion chemical vapor deposition process from a single solution containing all precursors. Bilayer solid oxide fuel cells (SOFC) anodes of different porosity were fabricated by copressing of NiO-GDC powder and SnO 2 -NiO-GDC composite powder. Porosity variation in the anodes was achieved by the removal of the SnO 2 -phase during firing and subsequent cell testing. Anode-supported SOFC single cells were constructed and tested for electrochemical performance. Interfacial polarization resistances of a cell with the bilayer anode were 1.20, 0.49, 0.22, and 0.1 Ω cm 2 at 500, 550, 600, and 650°C, respectively, demonstrating peak power densities of 171, 301, 441, and 544 mW/cm 2 , respectively.

A Highly Sensitive and Fast-Responding SnO2 Sensor Fabricated by Combustion Chemical Vapor Deposition

Highly porous and nanostructured SnO2 thin-film gas sensors with Pt interdigitated electrodes have been fabricated via a combustion chemical vapor deposition process. The SnO2 films were less than 1 μm thick and consisted of nanocrystallines smaller than 30 nm. At 300 °C, the as-prepared SnO2 gas sensor showed a sensitivity of 1075 to 500 ppm ethanol vapor, and the corresponding response time and recovery time were 31 and 8 s, respectively. The extrapolated low detection limit appears to be below 1 ppm. Consequently, the as-fabricated sensor demonstrated significant improvements over those reported in the literature. These highly sensitive, fast-responding, and low-cost SnO2 sensors could have many practical applications.

Systematic microstructural investigation of alumina deposited by liquid fuel combustion chemical vapor deposition

An alumina organic-sol miscible to both organic and aqueous solutions was synthesized and used as a liquid feedstock in a combustion chemical vapor deposition process. An air-assisted atomizer allows the attainment of fine droplets with relatively low velocity toward the substrate. The ignited spray heats the substrate above 1000 °C when placed at a distance of 12.5 cm from the atomizer. The microstructure of the films was noted to be strongly sensitive to the combustion stage of the droplets when they hit the substrates. The combustion stage was adjusted by a certain number of parameters, including the distance substrate-atomizer and the flammability of the liquid feedstock. When advanced stage of combustion is allowed, the deposited films were composed of fine particles with an average diameter between 200 and 400 nm. The non-completely burned droplets lead to the deposition of films with high porosity. In contrast, films formed with droplets in the liquid form exhibited dense structure. Finally, it was demonstrated that the improvement of the homogeneity of the films could be attained by using a minimal flow rate of the feedstock with low aluminum concentration.

Nanostructured and functionally graded cathodes for intermediate-temperature SOFCs

Nanostructured composite cathodes graded in both composition and microstructure have been successfully fabricated for the first time using a combustion chemical vapor deposition (CCVD) process. The functionally graded structures of these cathodes dramatically increase the rates of electrode reactions, enhance the transport of oxygen molecules to the active reaction sites, and significantly improve the compatibility between the electrodes and other cell components. As a result, extremely low interfacial polarization resistances and high power densities have been achieved at operating temperatures of 600–850°C, suggesting that the CCVD process has great potential for cost-effective fabrication of nanostructured fuel cell electrodes.

Candidate oxidation resistant coatings via combustion chemical vapor deposition

Oxidation and water vapor resistant coatings are needed to increase the life time of metallic and ceramic substrates for high temperature applications (>1000 ◦C). Oxides including yttria, tantalum oxide, and alumina are leading candidate materials that are being considered [1–5]. These coatings have been produced as thin films by chemical vapor deposition (CVD) and/or sol-gel methods [3–6]. Combustion CVD (CCVD) is another viable coating technology that has been developed to produce high-quality oxide and noble metal thin films [7–10]. In this CCVD process, precursors such as nitrates and acetylacetonates are dissolved in suitable aqueous or organic solvents to form a solution. This solution is delivered via a pump to the Nanomiser©R device that atomizes the solution into submicron droplets. These droplets are then carried or convected by oxygen or another suitable gas to a flame where they are vaporized and combusted. Coatings are deposited onto the substrate by rastering the flame plasma. The heat from the flame supplies the energy required to evaporate the atomized droplets, causing precursors to react or decompose to form the desired material while flowing to vapor deposit onto the substrate. The CCVD technique offers the advantage of producing single and multicomponent oxides with relative ease, thus providing a unique, competitive edge over conventional methods in rapidly developing oxides. Additionally, multilayering and doping of oxides can be easily accomplished. The features and benefits of the technology are expounded in detail elsewhere [7–9]. In this paper, we report the synthesis of tantalum oxide, yttria, and alumina coatings via CCVD. Generally speaking, precursors used in this study have low vapor pressure and high solubility (such as metal nitrates, acetylacetonates, and ethylhexanoates). These precursors were dissolved in suitable organic or inorganic solvents to form starting solution. This solution was used with the CCVD process to deposit coatings onto YSZ, fused silica and/or sapphire substrates. These substrates were used so that cross-sections could be readily produced via fracture. The substrate was mounted on the fixture with the flame aimed at it. The flame temperature was measured adjacent to the substrate via a thermocouple and depositions were done at flame temperatures ranging from 800 ◦C to 1300 ◦C and the substrate

The Progress on Low-Cost, High-Quality, High-Temperature Superconducting Tapes Deposited by the Combustion Chemical Vapor Deposition Process

ABSTRACTThe innovative Combustion Chemical Vapor Deposition (CCVD) process is a non-vacuum technique that is being investigated to enable next generation products in several application areas including high-temperature superconductors (HTS). In combination with the Rolling Assisted Biaxially Textured Substrate (RABiTS) technology, the CCVD process has significant promise to provide low-cost, high-quality lengths of YBCO coated conductor. The CCVD technology has been used to deposit both buffer layer coatings as well as YBCO superconducting layers. A buffer layer architecture of strontium titanate and ceria have been deposited by CCVD on textured nickel substrates and optimized to appropriate thicknesses and microstructures to provide templates for growing PLD YBCO with high critical current density values. The CCVD buffer layers have been scaled to meter plus lengths with good epitaxial uniformity along the length. A short sample cut from one of the lengths enabled high critical current density PLD YBCO. Films of CCVD YBCO superconductors have been grown on single crystal substrates with critical current densities over 1 MA/cm2. Work is currently in progress to combine both the buffer layer and superconductor technologies to produce high-quality coupons of HTS tape made entirely by the non-vacuum CCVD process.

Low-cost combustion chemical vapor deposition of epitaxial buffer layers and superconductors

A new low-cost, open-atmosphere deposition technique, combustion chemical vapor deposition (CCVD) is used to deposit epitaxial buffer layers and high-temperature superconductors on oxide single-crystal substrates. The CCVD process has the potential for manufacturing buffer layers and superconductors onto textured metal substrates in a continuous reel-to-reel production. CCVD does not use vacuum equipment or reaction chambers required by conventional techniques, while its coating quality rivals and even exceeds that of conventional methods. Compounds being studied with the CCVD process include the buffer layers cerium oxide (CeO/sub 2/), yttria stabilized zirconia (YSZ), strontium titanate (SrTiO/sub 3/), lanthanum aluminate (LaAlO/sub 3/), yttria (Y/sub 2/O/sub 3/), and ytterbium oxide (Yb/sub 2/O/sub 3/) and two rare earth superconductors, YBa/sub 2/Cu/sub 3/O/sub 7-x/, (YBCO) and YbBa/sub 2/Cu/sub 3/O/sub 7-x/ (YbBCO).

Platinum-Catalyzed Polymer Electrolyte Membrane for Fuel Cells

ABSTRACTThe objective of this research is to develop the combustion chemical vapor deposition (CCVD) process for low-cost manufacture of catalytic coatings for proton exchange membrane fuel cell (PEMFC) applications. The platinum coatings as well as the fabrication process for membrane-electrode-assemblies (MEAs) were evaluated in a single testing fuel cell using hydrogen/oxygen. It was found that increasing the platinum loading from 0.05 to 0.1 mg/cm2 did not increase the fuel cell performance. The in-house MEA fabrication process needs to be improved to reduce the cell resistance. Significantly higher performance of Pt coating by the CCVD process has been obtained by MCT's fuelcell industry collaborators who are more experienced with MEA fabrication. The results can not be revealed due to confidentiality agreements.

CCVD: Low-Cost Vapor-Deposition of Thin Films in Open Atmosphere

AbstractThe new, patented Combustion Chemical Vapor Deposition (CCVD) process holds promise for low cost, high throughput manufacturing of thin film ceramic coatings with composition and microstructure tailored for specific applications in electronic, optic, anti-corrosion and anti-wear applications. The flame-based CCVD process is an open-air, non-vacuum, environmentally friendly process with the ability to produce coatings of equal or superior quality to those produced by conventional vacuum-based methods. Capital and operating costs for CCVD coating systems are significantly lower than, for example, conventional CVD and PVD technologies. As an open-atmosphere process, ccvD can be easily implemented in a continuous production line environment, avoiding the need for vacuum load-locks. MicroCoating Technologies has used CCVD to deposit over 60 different inorganic materials onto a variety of substrates ranging from metals and polymers to ceramics. Multi-layered films of complex composition have been achieved with excellent stoichiometric control. We review the CCVD process and characteristics of representative coatings