Coating methods spin casting

Spin coating or spin casting is the preferred method for application of thin, xmiform films to flat supporting substrates. For this fabrication the conjugated polymer or its nanocomposite must be soluble or at least it should form fine suspension in common organic solvent. A schematic representation of spin-coating method is shown in Figure 12.13. 

Solution Deposition of Thin Films. Chemical methods of preparation may also be used for the fabrication of ceramic thin films (qv). MetaHo-organic precursors, notably metal alkoxides (see Alkoxides, metal) and metal carboxylates, are most frequently used for film preparation by sol-gel or metallo-organic decomposition (MOD) solution deposition processes (see Sol-GEL technology). These methods involve dissolution of the precursors in a mutual solvent control of solution characteristics such as viscosity and concentration, film deposition by spin-casting or dip-coating, and heat treatment to remove volatile organic species and induce crystaHhation of the as-deposited amorphous film into the desired stmcture. 

Many studies have used these methods for processing of both thermosetting and thermoplastic polymers. Y. Liao (53) dissolved epoxy in a well-dispersed, ultra-sonicated CNT suspension. The solvent was evaporated, and the epoxy was subsequently cured to form a nanocomposite in which the good CNT dispersion was achieved. Jin et al. (54) produced various types of polymer-coated and polymer-grafted MWNT solutions, in some cases evaporating the solvent and subsequently melt-mixing with another polymer. Yudasaka et al. (55) used a mixture of SWNTs and PMMA in monochlorobenzene (MCB) for dispersion, purification and subsequent spin-casting of the material. 

PVA, 88 mg) was mixed with 0.2 ml of HEPES buffer solution (1 x 10-2 mol dm 3 HEPES, 10 ml total) at pH 7.0 containing BCECF (5 mg) and stirred for several minutes at room temperature. The mixture was then cast on an ITO-coated quartz substrate by a spin-coating method, and water was removed by evaporation. A semitransparent aluminum (Al) film was deposited on the dried polymer film by a vacuum vapor deposition method. The ITO and Al films were used as electrodes. A sinusoidal ac voltage with a modulation frequency of 40 H z was applied to a sample polymer, and the field-induced change in fluorescence intensity was detected with a lock-in amplifier at the second harmonic of the modulation frequency. A dc component of the fluorescence intensity was simultaneously observed. 

Important processing methods vapor phase deposition, spin coating, injection molding, casting, ex-trusion, drawing of oriented films, compression molding, sintering... 

Several techniques, such as casting, spin-casting, and in situ deposition methods, can be used to produce polymer coated thin films, such as polyaniline and... 

For the evaluation of the SIM technique in chemical sensors application, an experimental set-up was developed as shown in Fig. 31. A fiber-optic chemical sensor was prepared, using polyaniline as the modified cladding for a short MM sensing fiber. The spin-casting method was used for coating a thin layer of polyaniline material on the fiber core surface. Then, the modified fiber was tested for the detection of HCl vapor and NH3 gas. The sensor was tested by both the total intensity modulation and the SIM techniques. 

Spin casting methods are used extensively in the microelectronics industry. We have adopted the best practices available to achieve full density thin films. The full density (po = 1.186 g/cm ) is used for PMMA, justified by measurement of the full refractive index at 632.8 nm n = 1.49) of our spin coated thin films to within = 0.02. The density of PVN was measured by gas pychnometry to be po = 1.34 g/cm somewhat different from the literature [67]. Although there is no literature value for n, the measured n = 1.50 0.03 compares well with the precursor polyvinylalcohol n = 1.52 [68]. An uncertainty in of 0.03 translates into a density uncertainty of 5% via the Lorentz-Lorenz equation, essentially p OC (n -l)/(n +2). Although the samples are likely to be full density, up to 5% porosity may be present (note that... 

Amorphous organic materials are divided into two categories compounds with low molecular weights, and polymers. Devices made from low-molecular-weight compounds are generally fabricated by vacuum deposition. Devices made from polymers are fabricated by the casting or spin-coating methods. 

The second type of photosensitive SWNT-FET devices adopts SWNT networks as the transistor channel. A polymer layer is then deposited over the contacts and nanotubes by a drop-casting or spin-coating method. As shown in Figure 3.6, the coating of photosensitive polymer doesn t significantly... 

The second approach is spin casting polymers onto a substrate surface. Examples include using polyimides and a PR called SU-8. The third method is resist etchback. The wafer is first spin coated with a PR to planarize the surface, followed by a blank plasma etch that has the same approximate etching rate of the PR as that of the underlying material (e.g., Si02) and produces a much more planar surface. 

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