Off-specular X-ray scattering studies of the morphology of thin films (original) (raw)
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Grazing-incidence transmission small angle X-ray scattering from thin films of block copolymers
Journal of Polymer Science Part B: Polymer Physics, 2013
Thin films of lamellar and cylindrical block copolymers are popular systems for low-cost nanolithography. To be useful as nanoscale templates, the lamellae or cylinders must be oriented perpendicular to the substrate. Domain orientations are usually characterized by microscopy measurements of the film surface, but these techniques cannot detect tilted, bent, or tortuous domains in the film interior. We report a simple method to quantify out-of-plane disorder in thin films of block copolymers based on a variant of grazing-incidence small angle X-ray scattering (GI-SAXS). A typical GI-SAXS experiment illuminates the center of a substrate-supported film at a grazing angle of incidence (near the film/substrate critical angle), and the strong reflected signal is interpreted with the distorted-wave Born approximation. In a new approach, the beam footprint is moved to the far edge of the sample, allowing the acquisition of a transmission pattern. The grazing-incidence transmission data are interpreted with the simple Born approximation, and out-ofplane defects are quantified through analysis of crystal truncation rods and partial Debye-Scherrer rings. Significantly, this study demonstrates that grazing-incidence transmission small angle Xray scattering can detect and quantify the buried defect structure in thin films of block copolymers.
Synchrotron Radiation News, 2002
Polymer thin films have numerous technical applications as functional coatings, the most prominent example being PMMA coatings for lithography of integrated circuits and micromechanical devices. Polymer blends and block copolymers can be tailored for specific mechanical, optical, electric, and chemical properties. For instance, functional surfaces have been created by means of polymer blend and diblock copolymer films which may serve as templates for nanolithography or as antireflection coatings . In the rapidly developing field of molecular electronics, opto-electronical properties of polymer films have been exploited and first devices have appeared on the market [3].
2010
A method is developed for calculating the small-angle x-ray scattering originating from within the interior of a thin film under grazing incidence illumination. This offers the possibility of using x-ray scattering to probe how the structure of polymers is modified by confinement. When the diffuse scattering from a thin film is measured over a range of incident angles, it is possible to separate the contributions to scattering from the interfaces and the contribution from the film interior. Using the distorted-wave Born approximation the structure factor, S͑q͒, of the film interior can then be obtained. We apply this method to analyze density fluctuations from within the interior of a silicon supported molten polystyrene ͑PS͒ film. Measurements were made as a function of film thickness ranging from one to ten times the polymer radius of gyration ͑R g ͒. The compressibility, calculated by extrapolating the measured S͑q͒ to q = 0, agrees well with that of bulk PS for thick films, but thinner films exhibit a peak in S͑q͒ near q = 0. This peak, which grows with decreasing thickness, is attributed to a decreased interpenetration of chains and a consequent enhanced compressibility.
2021
Electroactive polymer thin films undergo repeated reversible structural change during operation in electrochemical applications. While synchrotron X-ray scattering is powerful for the characterization of stand-alone and ex-situ organic thin films, in situ structural characterization has been underutilized--in large part due to complications arising from supporting electrolyte scattering. This has greatly hampered the development of application relevant structure property relationships. Therefore, we have developed a new methodology for in situ and operando X-ray characterization that separates the incident and scattered X-ray beam path from the electrolyte. As a proof of concept, we demonstrate the in situ structural changes of weakly-scattering, organic mixed ionic-electronic conductor thin films in an aqueous electrolyte environment, enabling access to previously unexplored changes in the pi-pi peak and diffuse scatter in situ, while capturing the solvent swollen thin film structu...
Analytical and Bioanalytical Chemistry, 2010
A combination of microbeam grazing incidence small angle X-ray scattering (μGISAXS) and imaging ellipsometry is introduced as a new versatile tool for the characterization of nanostructures. μGISAXS provides a local lateral and depth-sensitive structural characterization, and imaging ellipsometry adds the position-sensitive determination of the three-dimensional morphology in terms of thickness, roughness, refractive index, and extinction coefficient. Together μGISAXS and imaging ellipsometry enable a complete characterization of structure and morphology. On the basis of an example of buildup of nanostructures from monodisperse colloidal polystyrene nanospheres on a rough solid support, the scope of this new combination is demonstrated. Roughness is introduced by a dewetting structure of a diblock copolymer film with one block being compatible with the colloidal nanoparticles and one block being incompatible. To demonstrate the potential for kinetic investigations, μGISAXS and imaging ellipsometry are applied to probe the drying process of an aqueous dispersion of nanospheres on such a type of rough substrate.
2007
The second generation of a sample chamber designed for in situ measurement of temperature-and time-dependent polymer film nanostructure using the method of grazing incidence small angle x-ray scattering is presented. An increased operating temperature limit ͑from 260 to 400°C͒ with precise control ͑±0.1°C͒ at fixed temperatures as well as a fourfold increase in maximum instantaneous cooling rate ͑up to 73°C / s͒ relative to the first generation chamber ͓M. N. Groves et al, J. Appl. Crystallogr. 39, 120 ͑2006͔͒ are reported. Thermal quenches from 220 to 90°C are shown to be reproducible to within ±1°C of the final temperature. Experimental tests on spin-coated films of symmetric diblock styrene-butadiene copolymer demonstrate the ability to resolve the kinetics of orientation of lamellar domains parallel to the silicon substrate, distinct from the initial formation of randomly oriented lamellar domains immediately following the thermal quench.
Langmuir, 2015
The formation of Laser Induced Periodic Surface Structures (LIPSS) on model spin-coated polymer films has been followed in situ by Grazing Incidence Small Angle X-ray Scattering (GISAXS) using synchrotron radiation. The samples were irradiated at different repetition rates ranging from 1 up to 10 Hz by using the 4th harmonic of a Nd:YAG laser (266 nm) with pulses of 8 ns. Simultaneously GISAXS patterns were acquired during laser irradiation. The variation of both the GISAXS signal with the number of pulses and the LIPSS period with laser irradiation time is revealing key kinetic aspects of the nanostructure formation process. By considering