Ultra-thin

Because beryllium is relatively transparent to X-rays, ultra-thin Be-foil is finding use in X-ray lithography for reproduction of microminiature integrated circuits. 

Limited solubility in selected perfluorinated solvents (unique amongst commercial fluoropolymers), enabling solution-cast ultra-thin coatings in the submicrometre thickness range. 

Fig. 4.15. Angular dependence of the fluorescence radiation emitted from a Co-layered Si substrate. The Co-Ka intensity is plotted semi-logarithmically for layers of different thickness (mm). The maxima forthe ultra-thin Co-layers are located at the critical angle of Si (dashed vertical line). They are shifted to the critical angle of Co (dotted vertical line) ifthe layer is more than 10 mm thick ([4.21], after Ref [4.41]).

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. 

It will be clear that L-B films are intrinsically linked to self-assembly of molecules, and this has been recognised in the title of a recent overview book (Ulman 1991), An Introduction to Ultra thin Organic Films from Langnmir-Blodgett to Self-Assembly An Overview. 

As discussed above, it is desirable to use large, almost grazing angles of incidence in RAIR spectroscopy in order to maximize the sensitivity of the technique to ultra-thin films. Using such large angles of incidence usually requires the substrates to be at least a few centimeters in length. This severely limits the spatial... 

Most researchers were not apparently aware of earlier CNT preparations in the context of ultra-thin vapour-grown carbon fibres (VGCF). This type of CNT is termed pyrolytic (PCNT) and its preparation shows promise of large-scale synthesis. Needless to say, it is of practical importance to provide sufficient CNTs at reasonable cost. This chapter highlights the preparation methods, structural characteristics and current commercial status of PCNTs and includes a description of the devices used hitherto to obtain aligned PCNTs. By way of... 

The study of ultra-thin Fe thin films on Cu(OOl) substrate has attracted a lot of interest in the past. This is due to the abundance of interesting phenomena associated with this system. Due to the small epitaxial misfit a good layer by layer growth is expected stabilizing the film in a structure related to the fee phase of bulk Fe which is otherwise unstable at low temperatures It also become a test system for magnetic measurements. 

Figure 5-19. N(ls) XPS core level spectra of emeraldine base adsorbed on ITO. The top most spectrum corresponds to ultra-thin Him (in the mono layer regime) while the bottom spectrum corresponds to thick film.

Figure 5-21. N(ls) core level spectra of the iiniim model compound PC20X adsorbed on ITO. The upper curve corresponds to a thick film, the central curve to an intermediate thick film, and the lower curve to an ultra thin Him, essentially a mono-layer in thickness. The bold solid lines are the filled curves and the thin solid and dolled lines are the Gaussian peak components lor physisorbed and chemisorbed PC20X, respectively.

Ultra-thin films of polyanilinc may be spin-coaled 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 the... 

While thin polymer films may be very smooth and homogeneous, the chain conformation may be largely distorted due to the influence of the interfaces. Since the size of the polymer molecules is comparable to the film thickness those effects may play a significant role with ultra-thin polymer films. Several recent theoretical treatments are available [136-144,127,128] based on Monte Carlo [137-141,127, 128], molecular dynamics [142], variable density [143], cooperative motion [144], and bond fluctuation [136] model calculations. The distortion of the chain conformation near the interface, the segment orientation distribution, end distribution etc. are calculated as a function of film thickness and distance from the surface. In the limit of two-dimensional systems chains segregate and specific power laws are predicted [136, 137]. In 2D-blends of polymers a particular microdomain morphology may be expected [139]. Experiments on polymers in this area are presently, however, not available on a molecular level. Indications of order on an... 

Westlake, F. J., "An Interferometric Study of Ultra-Thin Fluid Films," Ph.D. thesis, Univ. of London, 1970. 

Subsequently, a lubrication theory considering the solvation force is deduced accordingly in such ultra-thin film lubrication. 

Pressure between solid walls separated by ultra-thin liquid film is then expressed as follows ... 

TFL is an important sub-discipline of nano tribology. TFL in an ultra-thin clearance exists extensively in micro/nano components, integrated circuit (IC), micro-electromechanical system (MEMS), computer hard disks, etc. The impressive developments of these techniques present a challenge to develop a theory of TFL with an ordered structure at nano scale. In TFL modeling, two factors to be addressed are the microstructure of the fluids and the surface effects due to the very small clearance between two solid walls in relative motion [40]. 

Tichy, J. A., Ultra Thin Film Structured Tribology," Proc. 1 st Int. Symp. Tribol. 19-23 Oct, 1993, Beijing, pp. 48-57. 

Wang, H. and Hu, Y. Z., Molecular Dynamics Study on Interfacial Slip Phenomenon of Ultra-thin Lubricating Films," presented 2XITC2000, Nagasaki, Japan, Oct. 2000. 

Meanwhile, study on ultra-thin film gas lubrication problems has become one of the most attractive subjects in the held of tribology during the past three decades. 

Since the middle of the 1990s, another computation method, direct simulation Monte Carlo (DSMC), has been employed in analysis of ultra-thin film gas lubrication problems [13-15]. DSMC is a particle-based simulation scheme suitable to treat rarefied gas flow problems. It was introduced by Bird [16] in the 1970s. It has been proven that a DSMC solution is an equivalent solution of the Boltzmann equation, and the method has been effectively used to solve gas flow problems in aerospace engineering. However, a disadvantageous feature of DSMC is heavy time consumption in computing, compared with the approach by solving the slip-flow or F-K models. This limits its application to two- or three-dimensional gas flow problems in microscale. In the... 

Modified Reynolds Equations for Ultra-Thin Film Gas Lubrication... 

The last category is the pressure-driven gas flows, which are typical in micro gas fluidic and micro heat transfer systems. Because the channel diameter or width in micro gas fluidic systems is in the scale of sub-micrometer or less, ultra-thin gas lubrication theory plays an important role in... 

Mitsuya, Y., Modified Reynolds Equation for Ultra-thin Film Gas Lubrication Using 1.5-order Slip-Flow Model and Considering Surface Accommodation Coefficient," ASME J. Tri- [25] fcoZ.,Vol. 115,1993, pp. 289-294. 

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