| 1. |
- Abdi, Y., et al.
(författare)
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Light-emitting nano-porous silicon structures fabricated using a plasma hydrogenation technique
- 2005
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Ingår i: Materials Science and Engineering B: Solid-State Materials for Advanced Technology. - : Elsevier BV. - 0921-5107. ; 124-125:SUPPL., s. 483-487
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Tidskriftsartikel (refereegranskat)abstract
- The preparation of porous silicon films by DC-plasma hydrogenation and subsequent annealing of amorphous silicon films on silicon and glass substrates is reported for the first time. The effects of varying plasma power and annealing temperatures have been investigated and characterized by scanning-electron microscopy, transmission-electron microscopy, and photoluminescence. A plasma density of about 5.5 W/m2 and hydrogenation-annealing temperatures of about 400 °C was found to be suitable for the formation of nano-crystalline silicon films with grain diameters of the order of 3-10 nm. The intensity and wavelength of the emitted visible light were found to depend on the hydrogenation and annealing conditions, and patterning of the silicon films using standard lithography allowed the creation of light-emitting patterns.
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| 2. |
- Nayeri, Moheb, 1979, et al.
(författare)
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Surface effects on the structure and mobility of the ionic liquid C(6)C(1)ImTFSI in silica gels
- 2014
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-683X .- 1744-6848. ; 10:30, s. 5618-5627
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Tidskriftsartikel (refereegranskat)abstract
- We report on how the dynamical and structural properties of the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide (C(6)C(1)ImTFSI) change upon different degrees of confinement in silica gels. The apparent diffusion coefficients of the individual ions are measured by H-1 and F-19 pulsed field gradient nuclear magnetic resonance (PFG-NMR) spectroscopy, while the intermolecular interactions in the ionogels are elucidated by Raman spectroscopy. In addition, the local structure of the ionic liquid at the silica interface is probed by solid-state NMR spectroscopy. Importantly, we extend this study to a wider range of ionic liquid-to-silica molar ratios (x) than has been investigated previously, from very low (high degree of confinement) to very high (liquid-like gels) ionic liquid contents. Diffusion NMR measurements indicate that a solvation shell, with a significantly lower mobility than the bulk ionic liquid, forms at the silica interface. Additionally, the diffusion of the C(6)C(1)Im(+) and TFSI- ions decreases more rapidly below an observed molar ratio threshold (x < 1), with the intrinsic difference in the self-diffusion coefficient between the cation and anion becoming less pronounced. For ionic liquid molar ratio of x < 1, Raman spectroscopy reveals a different conformational equilibrium for the TFSI- anions compared to the bulk ionic liquid, with an increased population of the cisoid isomers with respect to the transoid. Concomitantly, at these high degrees of confinement the TFSI- anion experiences stronger ion-ion interactions as indicated by the evolution of the TFSI- characteristic vibrational mode at similar to 740 cm(-1). Furthermore, solid-state 2D Si-29{H-1} HETCOR NMR measurements establish the interactions of the ionic liquid species with the silica surface, where the presence of adsorbed water results in weaker interactions between Si-29 surface moieties and the hydrophobic alkyl protons of the cationic C(6)C(1)Im(+) molecules.
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