Structures in Thin Films

In situ observation of monolayer polymer crystals with thickness == 10-50 nm growing in a molten film of thickness d == 10 pm is generally unrewarding because the optical contrast is very small. One method to overcome this challenge is self-decoration as first carried out by Kovacs and Gonthier [57]. A poly (ethylene oxide) fraction, M = 3 kDa, was slowly crystallized as 

With decreasing T the faceting of hedrites becomes less evident, evolving to near circular flat-on lamellae [65, 66]. We return to hedrites in Section 3.4.3 when describing the evolution to coarse and then fine-textured spherulites at still lower crystallization temperatures where the diffusion length 5 = DIG decreases further. 

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Fig. 12—Density profile from simulations of liquid decane, the peaks in density and fluctuations across the film reveal the layering structure in thin films.

Bowden, N. Brittain, S. Evans, A. G. Hutchinson, J. W. Whitesides, G. M. 1998. Spontaneous formation of ordered structures in thin films of metals supported on an elastomeric polymer. Nature 393 146-149. 

Also polymers which are not lithographically active have shown some useful properties. STM has been used to produce from 0.5 to 2 nm sized structures in thin films of polyvinyl alcohol [456]. The structures were shown to depend strongly on the relative humidity and their origin might involve electrochemical reactions. 

Optical Mode Structure in Thin Film Organic Structures. Optimization of Bilayer Geometries... 

Fig. 4a—d. Lamellar structures in thin films that are not considered further in detail in the present article a Thin film confined between inequivalent walls, where the lower one favors the B-rich domains and the upper one the A-rich domains. Then an arrangement where the interfaces run parallel to the walls requires that thickness D and wavelength X are related as D=(n+1/2)A, n=0,l, 2... b Thin film on a substrate that favors B-rich domains undergo at the order-disorder transition (ODT) of the block copolymer melt a phase separation into a fraction x of thickness nXh and a fraction 1-x of thickness (n+1) Xh, such that D=[xn+(l-x) (n+l)] K if the air also favors B-rich domains, c If the air favors A-rich domains instead, the phase separation happens in a fraction x of thickness (n-l/2)A and a fraction 1-x of thickness (n+ 1/2)X with n= 1,2,3... d If the block copolymer film undergoes dewetting at the substrate, droplets form with a step-pyramide like structure ( Tower of Babel [30]). 

Nikolov, A.D. Wasan, D.T. Ordered micelle structuring in thin films formed from anionic surfactant solutions. J. Coll. Interface Sci. 1989, 133 (1), 1-12. 

Buseck PR (1992) Minerals and reactions at the atomic scale Transmission electron microscopy. Reviews in Mineralogy. Vol 27. Mineralogical Society of America, Washington DC Calmano W, Mangold S, Welter E (2001) An XAFS investigation of the artefacts caused by sequential extraction analyses of Pb-contaminated soils. Fres J Anal Chem 371 823-830 Carlson L, Schwertmann U (1981) Natural ferrihydrites in surface deposits from Finland and then-association with silica. Geochim Cosmochim Acta 45 421-429 Castaner R, Prieto C (1997) Fluorescence detection of extended X-ray absorption fine structure in thin films. J Phys III 7 337-349... 

Domain wall structures in thin films and small particles can be different from those in massive samples, because some energy contributions may become significant when sample dimensions are decreased. In thin films, the magnetisation vector tends to remain parallel to the film plane to avoid any contribution to the magnetostatic energy. The spins within a domain wall also rotate within the film plane, which leads to Neel walls. Fig. 4.31. Neel walls appear in thin films below a critical thickness limit. 

T.D. Choudhury, N.V.S. Rao, R. Tenent, J. Blackburn, B. Gregg, I.I. Smalyukh, Homeotropic alignment and director structures in thin films of triphenylamine-based discotic liquid crystals controlled by supporting nanostructured substrates and surface confinement. J. Phys. Chem. B... 

Experimental results on the band dispersion in o-bond polymers are very limited due to difficulty in preparing thin films with oriented chains [20, 31, 32, 62]. Here, we introduce the band dispersion of quasi-one-dimensional polymer polyethylene. Early work on the band structure study was carried out on systems with alkyl chains and was aimed at understanding the electronic structure of polyethylene, in particular, the possible existence of one-dimensional band structure in thin films where molecular chains assemble via weak interchain interactions. There is renewed interest in the band dispersions as they determine carrier transport properties in nanoscale molecular electronics [63]. 

Marden and Koch (1970) showed by resistivity. X-ray diffraction and dila-tometry that Sm transforms from the room temperature rhombohedral form to another close packed form at about 600 C. The high temperature form was shown to be hep. They also observed that the transition temperature was purity dependent. Further studies by DTA in our laboratory on Sm with the purity listed in table 2.5 gave the transition temperature listed in table 2.14 which is considerably higher than the 600°C reported by Mardon and Koch (1970). Kumar and Srivastava (1969) observed an hep structure in thin films of Sm by electron diffraction. The lattice parameters which they determined were considerably larger than those reported by Mardon and Koch (1970). Boulesteix et al. (1970a) observed Sm to be dhcp in a study of thin films by X-ray diffraction. However, the X-ray data of Mardon and Koch (1970) on bulk samples showed that the hep form is the stable form between the low temperature rhombohedral form and the high temperature bcc allotrope. 

There have been several papers which have appeared in the last five years concerning unusual lattice parameters and crystal structures in thin films of the rare earth metals. It is believed that these results are for highly contaminated metal which results from the high reactivity of the metallic rare earth thin films with residual gaseous impurities in the high vacuums [ 10" Torr (10 Pa)], Boulesteix et al. (1970b) and Gasgnier et al. (1974) have shown many of these structures to be impurity induced. 

In order to investigate whether formation and dissolution of the ordered structures in thin film solutions can be controlled by simply changing the vapor pressure of a protic non-solvent, more complex off-equilibrium experiments were designed. Experiments were performed under dry air conditions and in a vapor... 

Duan Y, Zhang Y, Yan S and Schultz J M (2005) In situ AFM study of the growth of banded hedritic structures in thin films of isotactic polystyrene. Polymer 46 9015-9021. 

This chapter focuses on polyferrocenylsilanes (PFSs) where iron and silicon are in the main chain. Subsequently, PFS block copolymers will be reviewed. These materials represent an area of rapidly growing interest as a result of their self-assembly into phase-separated metal-rich nanodomain structures in thin films and micelles in block-selective solvents. The resulting nanostructured materials have a wealth of potential applications and recent breakthroughs in this area are discussed. The subject matter of the chapter is divided up into subsections covering PFS homopolymer and block copolymer synthesis, solution and solid-state self-assembly and applications of the latter, which have been extensively developed by ourselves and our collaborators and also by other research groups. 

Slep D, Asselta J, Rafailovich MH, Sokolov J, Winesett DA, Smith AP, Strzhemechny Y, Schwarz SA, Sauer BB. Phase separation of polystyrene and bromo-polystyrene mixtures in equilibrium structures in thin films. Langmuir 1998 14 4860-4864. 

PHASE STRUCTURES IN THIN FILMS OF NANOSTRUCTURED POLYMER BLENDS... 

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