Controlling the crystallinity and nonlinear optical properties of transparent TiO<sub>2</sub>–PMMA nanohybrids

Yuwono, Akhmad Herman; Liu, Binghai; Xue, Junmin; Wang, John; Elim, Hendry Izaac; Ji, Wei; Li, Ying; White, Timothy John

doi:10.1039/b403530e

Cited by 148 publications

(122 citation statements)

References 42 publications

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“…Another way for recrystallization is to increase the annealing time at a relatively low temperature. For example, Yuwono et al 24 reported that amorphous TiO 2 grown by sol-gel could turn into anatase by annealing at 150 C for 24 h. By carefully examining the refractive index peaks of all the tested samples, an additional small pike can be observed for each of the crystallized samples at the wavelength of around 300 nm and the shifting of the peak positions was also noticed. In order to understand such evolution, the spectra of their extinction coefficient (k) were plotted in Fig.…”

Section: B Deposition Rate and Optical Propertiesmentioning

confidence: 96%

Characterization of low temperature deposited atomic layer deposition TiO2 for MEMS applications

Huang

Pandraud

Sarro

2012

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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TiO 2 is an interesting and promising material for micro-/nanoelectromechanical systems (MEMS/ NEMS). For high performance and reliable MEMS/NEMS, optimization of the optical characteristics, mechanical stress, and especially surface smoothness of TiO 2 is required. To overcome the roughness issue of the TiO 2 films due to crystallization during deposition at high temperatures (above 250 C), low temperature (80-120 C) atomic layer deposition (ALD) is investigated. By lowering the deposition temperature, the surface roughness significantly decreases from 3.64 nm for the 300 C deposited crystalline (anatase phase) TiO 2 to 0.24 nm for the 120 C amorphous TiO 2 . However, the layers deposited at low temperature present different physical behaviors comparing to the high temperature ones. The refractive index drops from 2.499 to 2.304 (at 633 nm) and the stress sharply decreases from 684 to 133 MPa. Superhydrophilic surface is obtained for the high temperature deposited TiO 2 under ultraviolet illumination, while little changes are found for the low temperature TiO 2 . The authors demonstrate that by suitable postdeposition annealing, all the properties of the low temperature deposited films recover to that of the 300 C deposited TiO 2 , while the smooth surface profile (less than 1 nm roughness) is maintained. Finally, micromachining of the low temperature ALD TiO 2 by dry etching is also studied.

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Section: B Deposition Rate and Optical Propertiesmentioning

confidence: 96%

Characterization of low temperature deposited atomic layer deposition TiO2 for MEMS applications

Huang

Pandraud

Sarro

2012

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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“…Potential applications could be in displays, waveguides, and solar cells' frequency converters, as well as nonlinear optical applications such as logic elements in nanoscale optoelectronic circuitry. [5][6][7][8][9] The main disadvantage of polymeric nanocomposites is visible light scattering due to the particle domains in the transparent polymeric medium. The sharp refractive indices increasing at the polymer-pigment particle interface cause optical scattering and the transmittance of the composites is remarkably reduced.…”

Section: Introductionmentioning

confidence: 99%

Anomalous transmittance of polystyrene–ceria nanocomposites at high particle loadings

Parlak

Demir

2013

J. Mater. Chem. C

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Optical nanocomposites based on transparent polymers and nanosized pigment particles have usually been produced at low particle concentrations due to the undesirable optical scattering of the pigment particles. However, the contribution of the particles to many physical properties is realized at high concentrations. In this study, nanocomposites were prepared with transparent polystyrene (PS) and organophilic CeO 2 nanoparticles using various compositions in which the particle content was up to 95 wt%. The particles, capped by 3-methacryloxypropyltrimethoxysilane (MPS), were dispersed into PS and the transmittance of the spin-coated composite films was examined over the UV-visible region.When the particle concentration was <20 wt%, the transmittance of the films showed a first-order exponential decay as the Rayleigh scattering theory proposes. However, a positive deviation was observed from the decay function for higher particle contents. The improvement in transmittance may be a consequence of interference in the multiple scattering of light by the quasi-ordered internal microstructure that gradually develops as the particle concentration increases.

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“…For example, for the same PMMA matrices, TiO 2 embedded nanocrystals (NC) give 2260 cm/GW (at least two order larger). 1 For the ZnS NP, the enhancement achieves about 230 cm/GW. 2 For comparison in the bulk ZnS crystals, this coefficient is equal to only 0.02 cm/GW, which confirms its nanosized origin.…”

mentioning

confidence: 99%

Low-Temperature Anomalies of Two-Proton Absorption in In₂O₃ Nanocrystals Incorporated into PMMA Matrixes

Kityk¹,

Liu²,

Sun³

et al. 2008

J. Phys. Chem. B

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Pages 8219-8222: Several additional clarifications and extensions concerning the obtained nonlinear optical data and several measurement details in the article Kityk, I. V.; Liu, Q.; Sun, Z.; Fang, J. J. Phys. Chem. B 2006, 110, 8219 will be given.The obtained value of the TPA (about 90 cm/GW) is of the same order as for other semiconducting nanocomposites. For example, for the same PMMA matrices, TiO 2 embedded nanocrystals (NC) give 2260 cm/GW (at least two order larger). 1 For the ZnS NP, the enhancement achieves about 230 cm/GW. 2 For comparison in the bulk ZnS crystals, this coefficient is equal to only 0.02 cm/GW, which confirms its nanosized origin. Even for such nonpromising nonlinear crystals as GaAs without the polymer covering sheets, the value of the TPA is equal up to 40 cm/GW, which is larger than for many organic materials. 3 The optimal content of the chromophore (about 4.3%), which usually do not exceed 5.4% for typical semiconducting nanocrystallite-polymer composites (in weight), corresponds to maximal content at which the NC aggregation do not occur yet. Usually for larger NC contents, one can observe drastic enhancement of the scattered light. This aggregation diminishes the NLO output and this chromophore NC content is very close for many inorganic NC incorporated into the polymer matrices (see for example SiC/PMMA composites 4 ). In the case of the IR spectral wavelengths, additional favoring factor of the nonlinear optical susceptibility enhancement (up to 5 orders) for such nanosized structure is caused by polaronic effects (see for example ref 5). Physical mechanisms determining the observed effects were described elsewhere (see for instance ref 6 and reference there).Recently also it was established that the principal role for such kinds of the nanocomposites play the sheets with thickness from 0.5 up to 5 nm on the borders separating the nanocrystallites and the surrounding polymers. This fact was unambiguously established following the ab initio molecular dynamics and quantum chemical simulations in refs 7 and 8. So effectively we deal with a nanoporous composite material, principally different from amorphous. The influence of the nanosurfaces on the NLO susceptibilities was demonstrated many times experimentally and theoretically (see for example refs 9 and 10). For example for semiconducting CdTe nanocomposites, an enhancement of at least two order of the third-order susceptibilities was observed compared to the bulk one. 11 This origin of the nonlinear optical susceptibility is principally different with respect to the organic materials where local hyperpolarizabilities (both of the second as well as of the third order ones) possess a principal theoretical limit. 12 Moreover, in several types of metallic nanoparticles, enhancement of the third-order susceptibilities may achieve even 5-6 orders, 13 and the role of the nanoconfined effects on the interfaces is crucial.The technology of preparaing optically homogeneous nanocomposites always includes several field alignments causing ...

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Controlling the crystallinity and nonlinear optical properties of transparent TiO₂–PMMA nanohybrids

Cited by 148 publications

References 42 publications

Characterization of low temperature deposited atomic layer deposition TiO2 for MEMS applications

Characterization of low temperature deposited atomic layer deposition TiO2 for MEMS applications

Anomalous transmittance of polystyrene–ceria nanocomposites at high particle loadings

Low-Temperature Anomalies of Two-Proton Absorption in In₂O₃ Nanocrystals Incorporated into PMMA Matrixes

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Controlling the crystallinity and nonlinear optical properties of transparent TiO2–PMMA nanohybrids

Cited by 148 publications

References 42 publications

Characterization of low temperature deposited atomic layer deposition TiO2 for MEMS applications

Characterization of low temperature deposited atomic layer deposition TiO2 for MEMS applications

Anomalous transmittance of polystyrene–ceria nanocomposites at high particle loadings

Low-Temperature Anomalies of Two-Proton Absorption in In2O3 Nanocrystals Incorporated into PMMA Matrixes

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Controlling the crystallinity and nonlinear optical properties of transparent TiO₂–PMMA nanohybrids

Low-Temperature Anomalies of Two-Proton Absorption in In₂O₃ Nanocrystals Incorporated into PMMA Matrixes