Synchrotron X-ray Reflectivity Study on the Structure of Templated Polyorganosilicate Thin Films and Their Derived Nanoporous Analogues

Abstract

Comprehensive X-ray reflectivity (XR) studies were conducted to characterize the structure of thin polyalkylsilicate films made of a poly(methylsilsesquioxane-co-ethylenylsilsesquioxane) precursor containing a star-shaped poly( -caprolactone) as a pore generator (porogen). The films were deposited on silicon wafer substrates by spin-coating and subsequently cured at various temperatures. Such spin-on glasses have a potential application as a low-dielectric-constant material for advanced semiconductors. Because highintensity synchrotron X-ray radiation was used, the XR data could be measured over 9 orders of magnitude in intensity, which facilitated the observation of fine structural details. A hierarchical fitting procedure for modeling the XR data is given. By evaluation of the critical angle of total reflection of the film material, which was observed at smallest angles, in particular the film electron density could be determined with a high accuracy. The films cured at 420 °C show a lower electron density as compared to those cured at 250 °C. This is explained by the fact that at the higher temperature the porogen is calcined and escapes from the films leaving behind a nanoporous structure. Film porosities could be estimated from the observed changes in the electron densities. From the very large number of high-frequency oscillations observed in the XR curves, it is concluded that the films exhibit a homogeneous, well-defined structure with small interface and surface roughness. The film thickness could be determined with an accuracy of (1 Å. The observation of an additional low-frequency modulation of the XR curves revealed a surface skin layer with a thickness of ca. 45 Å and with a slightly increased electron density as compared to the bulk of the film.

Well-defined and stable nanomicelles self-assembled from brush cyclic and tadpole copolymer amphiphiles: a versatile smart carrier platform

“…Synchrotron X-ray reflectivity measurements were conducted at the 3D beamline 33 of Pohang Accelerator Laboratory. Polymer thin films were prepared on silicon substrates via conventional spin coating and drying under vacuum at room temperature for 1 day; the individual polymers were dissolved in ethanol and filtered with polytetrafluoroethylene membrane filters (0.2 μm pore size).…”

“…The obtained reflectivity data were subjected to a geometrical correction and background subtraction procedure described in the literature. 33 The measured X-ray reflectivity data were quantitatively analysed with a recursive formula given by the Parratt dynamic theory. 33,34 RESULTS AND DISCUSSION Cyclic, tadpole and linear diblock copolymers of two monomers, ndecyl glycidyl ether and 2-(2-(2-methoxyethoxy)ethoxy)ethyl glycidyl ether, were synthesized and characterized as described in the Supplementary Information.…”

“…33 The measured X-ray reflectivity data were quantitatively analysed with a recursive formula given by the Parratt dynamic theory. 33,34 RESULTS AND DISCUSSION Cyclic, tadpole and linear diblock copolymers of two monomers, ndecyl glycidyl ether and 2-(2-(2-methoxyethoxy)ethoxy)ethyl glycidyl ether, were synthesized and characterized as described in the Supplementary Information. As summarized in Table 1, the PDGE and PTEGGE blocks in all brush copolymers were well controlled to have an equivalent degree of polymerization of 50 (±1).…”

High-performance triazole-containing brush polymers via azide–alkyne click chemistry: a new functional polymer platform for electrical memory devices

“…The measured data were subjected to geometrical correction and background subtraction using a procedure described in the literature. 34 …”

“…The sample-to-detector distances were 229.0 and 233.9 mm. In addition, synchrotron X-ray reflectivity (XR) analysis was conducted in θ-2θ scanning mode at the 3D beamline [34][35][36] of Pohang Accelerator Laboratory. An X-ray radiation source (λ = 0.1240 nm) was used, and the beam size at the sample position was 0.1 × 2.0 mm 2 .…”