Spin-coating

Dip coating is essentially a process akin to sol-gel deposition but differs from it by using a volatile suspension medium that quickly evaporates during withdrawing 

The coating thickness is mainly defined by the withdrawal speed v, by the solid content and the viscosity r of the liquid. If the withdrawal speed is chosen such that the shear rates keep the system in the Newtonian regime, the coating thickness h can be calculated by the Landau-Levich equation (Landau and Levich, 1942) as 

If reactive systems, as present in sol-gel type of coatings, are chosen for coating deposition using alkoxides or pre-hydrolysed systems, then control of the atmosphere is crucial as the atmosphere determines the evaporation rate of the solvent and the subsequent destabilisation of the sols. This leads to a gelation process and the formation of a transparent film due to the small (nanometre) particle size in the sols (Brinker, Hurd and Ward, 1988 Scriven, 1988 Brinker and Scherer, 1990). 

Spin coating utilizes centrifugal forces created by a spinning substrate to spread a liquid evenly over its surface. Current applications are in photoresist technology for the microelectronic industry and in the manufacture of 

Spin coating has been used to fabricate cathode materials for Hthium-ion batteries [99-106]. Spin coaters are easy to operate and relatively economical since they 

There are various key parameters in the spin-coating process, including the viscosity of the sol, the rotation speed, the number of deposition steps, type of 

The spin coating technique has attracted interest, since it maintains many aspects of technical catalysts prepared by pore volume or incipient wetness impregnation, and simultaneously allows the interpretation and analysis in a similar way as the more well-defined model systems discussed above [30]. Here, a solution of the desired catalyst precursor is dropped onto a wafer covered with an oxide film, which is spun on a rotor to create a liquid layer of uniform thickness in order to mimic traditional wet impregnation preparation of catalysts. Control of the catalyst loading and particle size is to some degree achieved by varying the rotation speed, concentration, and vapor pressure of the solute. Still the method suffers, however, from many of the drawbacks associated with wet-impregnated model catalysts, which imparts detailed mechanistic studies. 

In the static spin process, a few volumes of solution is dropped onto the substrate and allowed to spread until it covers most of the surface. Once the liquid has reached a specified diameter the chuck is accelerated to a predetermined speed, on the order of 20,000 rpm. 

Mechanical protection Si02 Multistep process alternating dips and firings at 400°C increase thickness by 100 nm each cycle 

Chemical protection Si02 Great care in drying minimize cracking and crazing 

Transparent electrode In20s—Sn02 Single dip process 

Specific absorption Ti02—Si02 Cr20s—Si02 F02O3—Si02  

h=initial thickness, ( =angular velocity, p=density, r =viscosity, and t=time. As for example, 60 nm thin film can be obtained by spin coating of a stock solution of poly(2,5-dimethylaniline) (PDMA)-MWCNTs nanocomposite in chloroform with a concentration of 0.25 mg/ml at a speed of 250 rpm for 5 s and then at 1000 rpm for 10 s (for drying) [39]. 

Many techniques needed to be developed to create and monitor these new thin film systems. An accurate method for producing thin polymer films was the first objective of this thesis research. The proposed solution to the problem was spin coating. First a polymer solution was made and was pipetted onto the desired surface. Next, the 

Several variables can control the film thickness of the final product. Extrand looked at some of the experimental parameters in spin coating. The solvent used to make the solution does affect the final thickness of the film. Different viscosity and solubility can make PMMA films cast from a cyclohexane solution twice as thick as those cast from a toluene solution. The research also showed that thickness increased as spin speed decreased as would be expected. The amount of solution applied to the wafer did not affect the thickness as long as there was enough present to cover the surface. Any excess was simply flung off the surface by centripetal forces. 

---

Tetrathiafulvalene (TTE) has also been used in electrochromic devices. TTE-based polymers spin-coated onto transparent electrode surfaces form stable thin films with reproducible electrochromic properties (100). The slow response of these devices has been attributed to the rate of ion movement through the polymer matrix. 

The pursuit of further miniaturization of electronic circuits has made submicrometer resolution Hthography a cmcial element in future computer engineering. LB films have long been considered potential candidates for resist appHcations, because conventional spin-coated photoresist materials have large pinhole densities and variations of thickness. In contrast, LB films are two-dimensional, layered, crystalline soHds that provide high control of film thickness and are impermeable to plasma down to a thickness of 40 nm (46). The electron beam polymerization of CO-tricosenoic acid monolayers has been mentioned. Another monomeric amphiphile used in an attempt to develop electron-beam-resist materials is a-octadecylacryUc acid (8). 

Fig. 10. Formation of noncentrosymmetric multilayer film by combining self-assembly and a surface S 2 reaction, where R = (CH2)30H procedure I = spin-coating followed by annealing at 110°C and procedure II = reaction of Cl2Si0SiCl20SiCl2, ie, a dilute solution of 4-[A/,A/,-bis-(3-hydroxyprop5l)-aminophenylazo]-4 -pyridine on a benzyl chloride SAM surface was used, resulting in facile formation of SAMs having high...

Dip and Spin Coating. The dip coating technique described for webs can also be used to coat discrete surfaces such as toys and automotive parts. The surface to be coated is suspended on a conveyor and the part dipped into the coating solution. The surface is then removed, the coating drains, then levels to give the desired coverage. The object is then dried or cured in an oven. 

Fig. 12. Schematic of a polymer-coated crosslinked PDMS cap in contact with a polymer-coated flat surface. The PDMS cap is oxidized in 02-plasma, and the polymer layer is coated by solvent casting. On flat surface, the polymer layer is spin coated.

This characteristic of RAIR can be observed experimentally. Fig. 8 shows the transmission spectrum of polydimethylsiloxane (PDMS) while Fig. 9 shows the RAIR spectrum of a thin film of PDMS spin-coated onto a chromium substrate. It can be observed that the bands near 1024 and 1095 cm have similar intensities in the transmission spectra but the band at higher frequencies is clearly much more intense in the RAIR spectrum. This change in relative intensity when PDMS is deposited onto a reflecting substrate is related to optical effects and is not related to orientation effects. 

When PMMA was adsorbed onto an iron substrate, four components were not sufficient to explain the C(ls) spectrum (see Fig. 21b) and a fifth component had to be added at 288.1 eV as shown in Fig. 21c. This component was attributed to carboxyl groups, indicating that the ester groups were partially hydrolyzed. Similarly, Leadley and Watts found that there were five components in the C(ls) spectrum of PMMA spin-coated onto aluminum, copper, and nickel substrates 124]. 

Fig. 21. High-resolution XPS spectra of PMMA spin-coated onto (a) silicon and (b,c) iron. The C(ls) spectnim of PMMA on silicon was explained by four components but an additional component was needed to explain the C(ls) spectrum of PMMA on iron. Reproduced by permission of Gordon and Breach Science Publishers from Ref. [24].

Yang and Jenekhe [186,187] reported a successful solubilization of aromatic polyimines in organic solvents via their soluble coordination complexes, which facilitated their solution characterization by NMR and processing films and coatings by spin coating and other techniques. This has created opportunities for various studies of the aromatic polyimines. 

Experimental information for polymeric LED is sparse. A key problem for conventional lime-of-flighl studies is that the condition of generating a sheet of carriers whose spatial extension is small compared to the thickness of a = 100 nm film is difficult to meet. On the other hand, thick films fabricated, for instance, by solvent casting rather than by spin coating, may differ regarding their morphology and, concomitantly, the built-in-disorder. On the fundamental side, transport in... 

In Section 13.2, we introduce the materials used in OLEDs. The most obvious classification of the organic materials used in OLEDs is small molecule versus polymer. This distinction relates more to the processing methods used than to the basic principles of operation of the final device. Small molecule materials are typically coated by thermal evaporation in vacuum, whereas polymers are usually spin-coated from solution. Vacuum evaporation lends itself to easy coaling of successive layers. With solution processing, one must consider the compatibility of each layer with the solvents used for coating subsequent layers. Increasingly, multilayered polymer devices arc being described in the literature and, naturally, hybrid devices with layers of both polymer and small molecule have been made. 

Currem field characteristics measured wiih conjugated polymers sandwiched between an indium-tin oxide (ITO) anode and an aluminum cathode are usually hole dominated and are, consequently, appropriate for testing injection/lransport models for the case of unipolar current How. Data shown in Figure 12-1 refer to injection-limited currents recorded on typically 100 nm thick spin-coated films of derivatives of poly(y d/"fi-phenylenevinylene) (PPV) and a planarized poly(/ /" -pheny-leue) employing a Keilhley source measure unit. The polymers were ... 

Fig. 8. X-ray reflection diagram of a thin polystyrene film on float glass [160]. The reflectivity R is plotted against the glancing angle . The film is spin coated from solution. A model fit (dashed line) to the reflectivity data is also shown where the following parameters are obtained film thickness = 59.1 0.1 nm, interface roughness glass-polymer = 0.4 0.1 nm, surface roughness polymer-air = 0.6+1 nm, mean polymer density = 1.05 + 0.01 g/cm-3. The X-ray wavelength is 0.154nm...

---