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Organic field-effect transistors (OFETs) were fabricated by depositing a regioregular poly(3-hexylthiophene) (P3HT) active layer using a dip-coating method. The field-effect mobility in OFETs depends on chain orientation and crystallinity and is related to direction and withdrawal speed with respect to the source/drain orientation. In this paper, how to control the structural and transport properties of P3HT films by coating parallel and perpendicular to the dipping direction is demonstrated. X-ray diffraction curves taken in the perpendicular direction exhibit a higher degree of crystalline ordering and edge-on conformation compared with those in the parallel direction; this finding correlates with the directional anisotropy of the OFET mobility. Both structural anisotropy and transport properties are enhanced upon thermal treatment. [ABSTRACT FROM AUTHOR]

Low-temperature casting of high molecular weight (HMW > 40 kDa) regioregular poly(3-hexylthiophene) (P3HT) is demonstrated to yield highly crystalline P3HT thin films with well defined and preferentially edge-on oriented [(100) contact plane] nanocrystallites on the pure and silanized Si/SiO2 substrates. Transmission electron microscopy and X-ray diffraction provide evidence for the increase in preferential edge-on orientation of P3HT-conjugated backbone while decreasing the film preparation temperature below room temperature. The optimum growth temperature is about −12°C for the given concentration (2 mg/mL in CHCl3). The reduced evaporation rate of the solvent results in a better selection of the thermodynamically stable orientation of nanocrystallites onto the substrate. The degree of preferential orientation and size of the crystallites can be further increased on n-octadecyltrichlorosilane-treated SiO2 substrates as well as by annealing the films at 200°C for 1 h. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

Abstract: We show that both the morphology and crystal structure of regioregular poly(3-hexylthiophene) (RR-P3HT) films in organic field effect transistor (OFET) devices with top surface contacts are altered, when an electric field is applied. Grazing incidence X-ray diffraction (GIXD) analysis reveals a dramatic decrease in structural order in the non-linear current regime and, by contrast, much less pronounced structural changes of the (h 00) peaks in the linear current regime. Using for the first time resonance soft X-ray reflectivity (RSoXR) on RR-P3HT to avoid radiation damaged and to enhance the scope of the attained depth resolved information, we show that these changes are located in a several tens of nanometer thin sub-surface layer of the active polymer in the device. Furthermore, the RSoXR data reveal that the changes are strongly related to the C 1s→ π ∗ and C 1s→ σ ∗-resonances. In situ AFM measurements of the RR-P3HT device surface support the reciprocal space analysis results by showing a substantial softening and lateral expansion of the RR-P3HT films, when 20V are applied between the contacts. These morphological and structural changes are partially reversible in nature. [Copyright &y& Elsevier]

Calcium titanate-CaTiO3 (perovskite) has been used in various industrial applications due to its dopant/doping mechanisms. Manipulation of defective grain boundaries in the structure of perovskite is essential to maximize mechanical properties and stability; therefore, the structure of perovskite has attracted attention, because without fully understanding the perovskite structure and diffracted planes, dopant/doping mechanisms cannot be understood. In this study, the areas and locations of atoms and diffracted planes were designed and investigated. In this research, the relationship between Young's modulus and planar density of unit cell, super cells (2 × 2 × 2) and symmetry cells of nano CaTiO3 is investigated. Elastic constant, elastic compliance and Young's modulus value were recorded with the ultrasonic pulse-echo technique. The results were C11 = 330.89 GPa, C12 = 93.03 GPa, C44 = 94.91 GPa and E = 153.87 GPa respectively. Young's modulus values of CaTiO3 extracted by planar density were calculated 162.62 GPa, 151.71 GPa and 152.21 GPa for unit cell, super cells (2 × 2 × 2) and symmetry cells, respectively. Young's modulus value extracted by planar density of symmetry cells was in good agreement with Young's modulus value measured via ultrasonic pulse-echo. [ABSTRACT FROM AUTHOR]

The impact of thermal annealing on the growth of crystallinenanodomainsof poly(3-alkylthiophene) (P3AT) in thin films (15–20 nm thick)was investigated as a function of length of alkyl side chain by combinedlow-dose high-resolution transmission electron microscopy (HR-TEM)and grazing incidence X-ray diffraction (GIXD). Statistical analysisof the data yields the characteristic dimensions of the face-on orientedP3AT nanocrystals, i.e., average stem length lcalong backbones and lateral dimension perpendicular to thestems laalong side chains. The followingtrends were identified: (i) in as-spin-coated films, the proportionof face-on oriented nanocrystals increases with the number of carbonatoms in the side chain, (ii) annealing favors the lateral in-planegrowth of the nanocrystals along the side chain direction (aP3ATaxis), (iii) for a given P3AT, the proportion offace-on oriented domains increases with annealing temperature, (iv)lateral growth along the aP3ATaxis is mostefficient for the longer octyl side chains, and (v) thermal annealinginduces only modest lamellar thickening which is limited by the poorslide diffusion of π-stacked P3AT chains as opposed to lateralgrowth favored by weak van der Waals interactions between layers of n-alkyl side chains. The increase in the population of face-onoriented crystallites, observed when the length of the side chainincreases, coincides with a corresponding decrease in the field effectmobility in annealed P3AT thin films. [ABSTRACT FROM AUTHOR]

Different techniques for a relatively fast self-assembledmonolayerfilm formation such as Langmuir–Blodgett (LB), spin-coating,and dip-coating methods have been compared using chloro[11-(5′′′′-ethyl-2,2′:5′,2″:5‴,2‴:5‴,2′′′′-quinquethiophene-5-yl)undecyl]dimethylsilaneas a reactive precursor. It was shown that both spin-coating and LBtechniques are very promising methods for preparation of highly orderedmonolayer films of organosilicon-functionalized quinquethiophene withvertical orientation of oligothiophene fragments, while dip-coatinggives only partial coverage. Optimal conditions for complete fillingout the substrate surface by the quinquethiophene-containing monolayerby spin-coating and LB methods have been found. Grazing incidenceX-ray diffraction measurements confirmed formation of in-plane crystallineorder within the monolayer film. Changes in the layer structure wereestablished by X-ray reflectivity and grazing incidence X-ray diffractionmethods. [ABSTRACT FROM AUTHOR]