Relationships between the solution and solid-state properties of solution-cast low-k silica thin films

Abstract

This paper reports on the fabrication of low-k (amorphous) silica thin films cast from solutions without and with two different types of surfactants (TWEEN® 80 and Triton™ X-100) to elucidate the relationships between the structural/morphological features of the casting solutions and the physical properties of the resulting thin films. Cryogenic transmission microscopy (cryo-TEM), static/dynamic light scattering (SLS/DLS), and small-angle X-ray scattering (SAXS) revealed contrasting colloidal dispersion states and phase behavior among the three casting solutions. Casting solution with the Triton™ X-100 surfactant produced stable (>90 days) nanoparticles with good dispersion in solution (mean particle size ∼10 nm) as well as good mesopore volume (characterized by nitrogen physisorption) in powder and thin films of high mechanical strength (characterized by the nanoindentation test). The longer main chain and bulkier side units of the TWEEN® 80 surfactant led to stable micelle-nanoparticle coexisting dispersion, which resulted in the highest mesopore volume in powder and thin films with the lowest dielectric constant (∼3) among the samples in this study. The casting solution without the surfactant failed to produce a stabilized solution or thin films of acceptable uniformity. These findings demonstrate the possibility of fine-tuning low-k silica film properties by controlling the colloidal state of casting solutions.

Highly Oriented Thin Membrane Fabrication with Hierarchically Porous Zeolite Seed

“…50 Integration of 29 Si MAS NMR signals allows calculation of the Q 4 /Q 3 ratio. Moreover, analysis of Q 4 / Q 3 gives quantitative information about silanols group formation due to silicon atoms extraction from TS-1 framework. Compared to TS-1, HTS displays a lower Q 4 /Q 3 ratio, indicating increased silanol group (SiO) 3 SiOH in HTS.…”

“…Zeolite membranes/films are ideal membrane/film materials because they have uniform, molecular-size pores (i.e., 0.3–1.3 nm) and excellent thermal, mechanical, and chemical stability. − Those properties enable their potential in many applications such as separation and catalytic reactions . Generally, superior separation performance is related to a high quality oriented zeolite membrane with a thin structure. − Such zeolite membranes are usually prepared by a seeded (secondary) growth method. − The process is considered as a typical crystal growth on the interface between the sol–gel solution and porous solid substrate.…”

Atmospheric Pressure Plasma Jet-Assisted Synthesis of Zeolite-Based Low-k Thin Films

“…Zeolite crystals have intrinsic micropores (pore size < 2 nm); therefore, we surmise that the mesopores can be attributed to interstitial spacing among the packed particles, imparted by the addition of TWEEN 80. 39,57 The mesopore size distributions as well as the mesopore volume derived from the nitrogen physisorption isotherms are presented in the Supporting Information (Figure S2 and Table S1). The high pore volume of samples with APPJ treatment (mainly mesopores) may explain the low k values of these samples.…”