The regioregular highly head-to-tail-coupled poly(3-alkylthiophene) (HT-P3AT) films were prepared by a friction-transfer technique. Polarized UV−vis absorption spectroscopy and grazing incidence X-ray diffraction (GIXD) were used to study the polymer molecular arrangement in the friction-transferred HT-P3AT films, and scanning electron microscopy (SEM) was used to observe the film surface morphology. The polarized UV−vis absorption spectra show a large dichroism regarding the drawing direction of friction-transfer. The order parameter is evaluated close to unity, which is the ideal orientation state. GIXD measurements show that alkyl side chains lie in the film plane, and the polymer backbones are well-ordered along the drawing direction of friction-transfer within 10° for poly(3-hexylthiophene) and 13° for poly(3-dodecylthiophene) in the film plane. The polymer backbones form a layered structure with the stacking of thiophene rings normal to the film surface. The polymer molecules in the friction-transferred films are ideally arranged three-dimensionally.

A comparative study in molecular arrangements of the n-octadecyltrichlorosilane (OTS) monolayer prepared by the Langmuir method and the chemisorption methods were carried out on the basis of grazing incidence X-ray diffraction (GIXD) and X-ray reflectivity (XR) measurements. The OTS molecules in the Langmuir OTS monolayer uniformly tilt ca. 8-10°to the surface normal and packed in a hexagonal lattice with the (10) spacing of 0.412 nm. On the other hand, the OTS molecules in the chemisorbed OTS monolayer tilt ca. 15-17°to the surface normal and also crystallite orient randomly in the two-dimensional plane. The average magnitude of the (10) spacing of the chemisorbed OTS monolayer was ca. 0.417 nm. Direct evidence that the packing density of the Langmuir OTS monolayer was higher than that of the chemisorbed OTS monolayer was obtained by GIXD and XR measurements for the first time.

A small-angle x-ray scattering technique has been applied for characterizing pore-size distribution in porous low-κ dielectric films. The data are collected in reflection geometry using offset θ/2θ scans for avoiding strong specular reflections from the film surface and its substrate. The effects of refraction and reflection at the film surface and interface are corrected by the distorted wave Born approximation. A Γ-distribution mode is used to determine the pore-size distribution in a film. The technique has been used to analyze porous methyl silsesquioxane films. The pore sizes were found to disperse in the range from subnanometer to several nanometers, and the results agree well with those obtained by the N2 gas adsorption technique.

No abstract