Experimental study of the surface structure of diblock copolymer films using microscopy and x-ray scattering

Cai, Zhonghou; Huang, Keqing; Montano, P. A.; Russell, Thomas P.; Bai, Jiaming; Zając, G.

doi:10.1063/1.464165

Cited by 48 publications

(26 citation statements)

References 29 publications

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“…They measured the surface structure in realspace by atomic force and optical microscopies, which was compared with the results from the reciprocal space, i.e., specular and off-specular reflectivity profiles. 12 The height of the holes determined from the scattering and microscopic methods agreed well, although the internal morphology in the thin film was only assumed and left unclear. Thus, even though the reflectivity measurement is a very powerful technique, it always involves some kinds of assumption(s) due to the lack of complete real-space structural information.…”

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confidence: 48%

A Neutron Reflectivity Study on a Terraced Lamellar Morphology in a Block Copolymer Thin Film

Niihara

Matsuwaki

Torikai

et al. 2007

Polym J

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ABSTRACT:A microphase-separated structure of a poly(deuterated styrene-block-2-vinylpyridine) (dPS-b-P2VP) block copolymer thin film was studied by neutron reflectivity (NR). The spun-coated dPS-b-P2VP block copolymer (on a Si substrate) showed the coexistence of a minority thin lamellar layer (holes) dispersed in a majority thick layer. The ''terraced structure'' was formed due to the mismatch between the initial film thickness and the intrinsic lamellar periodicity of the dPS-b-P2VP block copolymer. The amount and height of the holes were evaluated using atomic force microscopy (AFM), transmission electron microscopy (TEM) and transmission electron microtomography (TEMT). The three-dimensional (3D) images obtained from the TEMT experiments clearly showed that the microphase-separated structure inside the thin film was homeotropically aligned. The thickness of the thick and the thin lamellar layers corresponded to ð5=2ÞL 0 and ð3=2ÞL 0 , respectively (L 0 is the lamella periodicity in the bulk state). The NR profile from the dPS-b-P2VP thin film, R exp , showed many distinctive scattering peaks. Based on the structural information obtained from the microscopy, a scattering length density profile along the depth direction, i.e., the direction normal to the film surface, b=v TEMT , was evaluated, which was then used as an initial profile in the conventional model fitting method. An excellent best-fit to R exp was obtained using b=v TEMT

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confidence: 48%

A Neutron Reflectivity Study on a Terraced Lamellar Morphology in a Block Copolymer Thin Film

Niihara

Matsuwaki

Torikai

et al. 2007

Polym J

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“…We may also d e k e the average form factor of each island where the integration is over the surface area (4) of the island, and a i is the in-plane component of a. If dJ is the fractional coverage of the surface by the islands, then it may be shown that [2] where The total surface area is A and represents the specular reflectivity, while the off-specular scattering is given by where s(%) represents the in-plane structure factor of the islands, (A is the total surface area.) The second term subtracts the contribution of the average island density, which contributes only to S S W (~) .…”

mentioning

confidence: 99%

Off-specular X-ray scattering studies of the morphology of thin films

Sinha

Feng

Melendres

et al. 1996

Physica A: Statistical Mechanics and its Applications

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We discuss the scattering of x-rays from thin films at a surface or interface decorated with a morphology of islands and how these effects manifest themselves in the specular reflectivity and the diflFuse (off-specular) scattering. We show how this technique has been used to study block copolymer films decorated with islands on the surface and the development of electrochemically induced pitting on a Cu electrode in an electrolyte solution.The availability of synchrotron radiation has made it possible to study in detail the in situ structure and morphology of films absorbed on solid or liquid surfaces. Specular x-ray reflectivity studies have been used to study the laterally averaged density profile of the films along the surface-noma1 direction, and off-specular scattering and grazing incidence diff-action have been used to study the in-plane structure. Scattering methods are in a sense complementary to various types of surface imaging microscopies, such as AFM, STM, etc., but have the advantage of being able to provide global statistical information about the surface without the need for digitizing and averaging the images. They also have the capabiIity to probe buried interfaces with very high resolution. In this paper, we shall review synchrotron scattering studies of the surface morphology and wetting properties of polymer films on solid substrates and of the morphology of pitted films obtained by the process of electrochemical corrosion.Consider a surface or interface consisting of a series of islands or pits on a flat reference interface as shown i n Fig. 1. The scattering process is indicated schematically.is the incident wavevector for the x-rays at grazing angle of incidence a, kl is the scattered x-ray wavevector at grazing angle of scattering p, and the wavevector transfx ij = k, -Go. We (A is the total surface area.) The second term subtracts the contribution of the average island density, which contributes only to S S W (~) .Thus the specular reflectivity yields information on the island height distribution function, while the off-specular yields the in-plane correlations between the islands. If there are strong nearest neighbor correlations, s(a) wiU have side peaks at finite ql, provided the distance between neighbors is within the x-ray coherence length across the surface (typically 10 y-20 p for a synchrotron experiment). In this sense, off-specular scattering is the analogue, for the in-plane structure, of small-angle scattering for bulk colloidal liquids (c.f the work of S.H. Chen and collaborators), but with far smaller 4'-vectors (and consequently much larger length scales) accessible. An expression that is more accurate than the Born approximation is that given by the so-called Distorted Wave Born Approximation (DWBA) [l] in which the scattered intensity is given by Here T(a) is the Fresnel transmission coefficient for the average surface at grazing angle of incidence a, and S(4) is the Born approximation expression with 4 replaced by its value inside the medium under the interface, i.e...

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“…These features were incorporated by into a layer (herein referred to as the “top stack”) consisting of a half layer of PDMS, a full layer of PS, and a second half layer of PDMS. The electron density of the top stack was reduced by an amount commensurate with surface coverage of islands or holes calculated from AFM height images . Only the layer thicknesses of PS and PDMS in the top stack and bottom stack and the interfacial roughness were allowed to change during fitting of the calculated reflection curves to the experimental XRR data.…”

Section: Methodsmentioning

confidence: 99%

Thin film confinement reduces compatibility in symmetric ternary block copolymer/homopolymer blends

Uddin

Jiang

Raymond

et al. 2018

J Polym Sci B Polym Phys

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The thin film phase behavior of ternary blends consisting of symmetric poly(styrene) (PS)‐b‐poly(dimethylsiloxane)(PDMS), PS, and PDMS was investigated using X‐ray reflectivity (XRR) and atomic force microscopy (AFM). This system is strongly segregated, and the homopolymers are approximately the same length as the corresponding blocks of the copolymer. The XRR and AFM data are used to quantify changes in domain spacing (L) and morphology evolution with increasing homopolymer content (Φ H). In 100 nm thick films, from Φ H = 0 to 0.20, the system maintains a perfect parallel lamellar structure and domains swell as predicted based on theory; however, from Φ H = 0.30 to 0.50, a morphology transition to a “dot pattern” morphology (tentatively identified as perforated lamellae) and mixed morphologies were observed before macrophase separation. In thicker films, dot patterns were observed for a broad range of Φ H before macrophase separation. The absence of the bicontinuous microemulsion phase reported for bulk blends and thin films of perpendicular lamellae and the presence of dot patterns/perforated lamellae are attributed to preferential migration of the PDMS homopolymer to the wetting layers located at the substrate and free air interfaces, which leads to an asymmetric composition within the film and morphology transition. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 1443–1451

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Experimental study of the surface structure of diblock copolymer films using microscopy and x-ray scattering

Cited by 48 publications

References 29 publications

A Neutron Reflectivity Study on a Terraced Lamellar Morphology in a Block Copolymer Thin Film

A Neutron Reflectivity Study on a Terraced Lamellar Morphology in a Block Copolymer Thin Film

Off-specular X-ray scattering studies of the morphology of thin films

Thin film confinement reduces compatibility in symmetric ternary block copolymer/homopolymer blends

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