Ultra-thin film coatings

Ellipsometry in the vacuum UV (< 190 nm) enables the analysis of materials for the next generation lithography (photoresist, AR coatings) at the latest exposure wavelengths (157 nm and 193 nm). The short wavelengths increase the sensitivity of ellipsometric measurements of ultra thin films (<10 nm). New prospects are expected for the analysis of thin metallic and dielectric layers. 

Plasma surface treatment of many polymers, including fabrics, plastics, and composites, often occurs. The production of ultra-thin films via plasma deposition is important in microelectronics, biomaterials, corrosion protection, permeation control, and for adhesion control. Plasma coatings are often on the order of 1 100 nm thick. 

Developments in modern CVD allow to improve the deposition of thin films and bulky coatings nevertheless, an additional major issue remains the building of nanostructured materials such as ultra-thin films or dispersed nanoparticles. For these applications, the control of the deposit at the atomic or nano-scale level is essential. Consequently, the role of surface chemistry occurring between the CVD precursor and the substrate, as well as the gas-phase main physical properties have to be indisputably clarified. 

It is of interest primarily for very uniform ultra-thin films and coatings (0.002-5 mils) in applications such as electrical resistors, thermistors, thermocouples, stator cores, connectors, fast-sensing probes, photo cells, memory units, dropwise steam condensers for recovery of sea water, pellicles for beam splitters in optical instruments, windows for nuclear radiation counters, panels for micrometeorite detection, dielectric supports for planar capacitors, encapsulation of reactive powders, and supports in x-ray and optical work. Any significant growth would depend upon a major breakthrough in process techniques and a consequent lowering in price. 

Wholly aromatic polyimides are highly thermally stable engineering plastics, and have been widely used as the reliable insulating materials in microelectronics. Recent developments in this field toward higher integration of devices required ultra thin films of polyimides. Minimum thickness of polyimide films cast by spin coating was about 0.1 Urn. 

Ultra-thin films of poly aniline may be spin-coated onto the ITO substrates. By studying thick films, spectra of the polymer itself are obtained. As the thickness of the polymer overlayer is reduced, some of the subtle details of the interface between the very thinnest possible polymer layer (essentially a mono-layer, in... 

However, ultra-thin films of unsubstituted polyaniline deposited on ITO glass electrode produced by dip coating, spin coating and the LB technique showed the most informative voltammetric characteristics. The single-layer LB films of polymer showed much better and reversible electrochromic activity on repeated scanning within up to 0,9 V in 1,0 M HCl solution than in electrochemically prepared materials [287],... 

GHI 12] GmMBEU C.M., SniA F., Ostaci R.V., et al., Crystalline vanadimn nitride ultra-thin films obtained at room temperature by pulsed laser deposition . Surface and Coatings technology, vol. 211, pp. 158-162, 2012. 

Soft magnetic composite particles of reduced iron coated with ultra-thin films of poly(p-xylylene) can be prepared by a CVD polymerization [47]. 

SEIRA and SERS are powerful techniques for stmctural characterization of ultra thin films and well-ordered monolayer on metal surfaces. Thin films at interfaces are prepared by different procedures and developed for various applications. The fabrication and characterization of ultra thin films is a permanent area of research where some of the most interesting subjects are (a) bilayers and monolayers at liquid-liquid interface, (b) adsorption monolayers and Langmuir (water-insoluble) monolayers at air-water interface, (c) adsorption films and self-assembled monolayers (SAMs) at liquid-solid interface and Langmuir-Blodgett Alms, cast (deposit) films and spin-coat films at air-solid interface. Studies about molecular organization of monolayers of porphyrins derivatives, of azamacrocy-cles and their metallic derivatives among the many SEIRA applications to films and interfaces, were published . 

The development of this coating technique has enabled the study of ultra-thin films with thicknesses that are of interest in gas separation membrane applications. Figure 3.4(a) presents the influence of aging time on the oxygen permeability coefficients of Matrimid films down to 18 nm in thickness prepared with the coating technique. Note that the quoted film thickness is the thickness of the glassy layer. 

Several available FTIR techniques such as attenuated total reflection [5-7] have been utilized for coatings hardened on a metal surface, diffuse reflectance [8] for ultra-thin films, and transmittance [9, 10] for clear or transparent coatings. The FTIR is useful for determining parameters such as residual porosity and molecular bonding. If used in concert with a microscope, excellent spatial resolution can be obtained. Hasik et al. [11] studied a polysiloxane-silsesquioxane system with FTIR spectroscopy while developing SiCO ceramic. The authors noticed the transformation in vibration bands, in their material, as a function of chemical compositions and temperature. A quartz crystal microbalance and reflection-absorption infrared spectroscopy (RAIR) was used to study silane reaction over oxidized aluminum surface [12]. 

Another common device used in the rubber industry is the thin film evaporator. This device is very often used in the manufacture of ultra-low molecular weight elastomers that are used in sealant applications or specialty coatings, and as processing aids in conventional rubber compounding processes. The thin film evaporator described earlier, has found a multitude of other industry applications, including food processing operations. 

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