title: 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.
authors.affiliation: Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan, Republic of China. dunyen@ntu.edu.tw.
authors.forename: Chao-Ching
authors.initials: CC
authors.lastname: Chiang
authors.affiliation: Department of Chemical Engineering, National Chung Cheng University, Chia-Yi 62102, Taiwan, Republic of China. chmcch@ccu.edu.tw.
authors.forename: Chien-You
authors.initials: CY
authors.lastname: Su
authors.affiliation: Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan, Republic of China. dunyen@ntu.edu.tw.
authors.forename: An-Chih
authors.initials: AC
authors.lastname: Yang
authors.affiliation: Electron Microscope Unit of Instrument Center, National Taiwan University, Taipei 10617, Taiwan, Republic of China.
authors.forename: Ting-Yu
authors.initials: TY
authors.lastname: Wang
authors.affiliation: Department of Chemical Engineering and Biotechnology, National Taipei University of Technology, Taipei 10608, Taiwan, Republic of China.
authors.forename: Wen-Ya
authors.initials: WY
authors.lastname: Lee
authors.affiliation: Department of Chemical Engineering, National Chung Cheng University, Chia-Yi 62102, Taiwan, Republic of China. chmcch@ccu.edu.tw.
authors.forename: Chi-Chung
authors.initials: CC
authors.lastname: Hua
authors.affiliation: Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan, Republic of China. dunyen@ntu.edu.tw.
authors.forename: Dun-Yen
authors.initials: DY
authors.lastname: Kang