Evaluation of Pore Structure in Pure Silica Zeolite MFI Low-<i>k</i> Thin Films Using Positronium Annihilation Lifetime Spectroscopy

Li, Shuang; Sun, Jianing; Li, Zijian; Peng, Huei; Gidley, David W.; Ryan, E. Todd; Yan, Yushan

doi:10.1021/jp048707l

Cited by 57 publications

(36 citation statements)

References 24 publications

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“…However the 0.36 nm zeolite micropore size is considerably smaller than that previous reported for MFI zeolites (containing no cations from synthesis) by PALS (0.55 nm±0.03 nm) [32], by low pressure N 2 adsorption (0.54 nm) [33] or by crystallography for the 10-member ring openings (0.56 nm) [6,30]. 0.36 nm measured in this work could be an average of the accessible intracrystalline spaces as the positrons can access both the 0.55 nm pores and the smaller surrounding chambers within the MFI lattice.…”

Section: Palscontrasting

confidence: 66%

“…The difference between this measured size and the reported (0.55 nm±0.03 nm) is in a reasonable range. Furthermore, the mesopores measured at 13.5 nm by PALS for high silica MFI zeolites (Table 1) are considerably larger than those from the literature [26,32]. This is likely to be due to the different synthesis conditions performed within different laboratories.…”

Section: Palsmentioning

confidence: 80%

“…The presence of these cations was not taken into account for the determination of the theoretical radius (0.55 nm) of the pure aluminosilicate structure [34,35]. Given that previously reported PALS results on MFI zeolite films yield a single uniform pore size of 0.55 nm±0.03 nm [32], the latter explanation is most likely. The partial occupancy and replacement behavior of Na + with K + may be the reason for the measured smaller pore size in the current work.…”

Section: Palsmentioning

confidence: 99%

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Designing hierarchical porous features of ZSM-5 zeolites via Si/Al ratio and their dynamic behavior in seawater ion complexes

Zhu

Doherty

et al. 2013

Microporous and Mesoporous Materials

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MFI-type zeolites were characterized using powder x-ray diffraction (XRD), and positron annihilation lifetime spectroscopy (PALS) to uncover the hierarchical porous * Corresponding author. Tel: +61 3 9919 7682; fax: +61 3 9919 7696. Email: mikel.duke@vu.edu.au (M. Duke). overall release of ions, principally Na + and K + , which were liberated mainly from the zeolite channels, yet these materials adsorbed Ca 2+ in the microporous grain boundaries and Mg 2+ in the mesoporous grain boundaries. Si/Al = 100 appeared to be a unique ratio, allowing the material to possess the same Na + adsorption features (and hydrophilicity) of high alumina materials, but ion interactions resembling high silica materials. MFI-type zeolite is therefore shown to be highly configurable using Si/Al ratio for a wide variety of applications in the presence of ions.

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Section: Palscontrasting

confidence: 66%

Section: Palsmentioning

confidence: 80%

Section: Palsmentioning

confidence: 99%

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Designing hierarchical porous features of ZSM-5 zeolites via Si/Al ratio and their dynamic behavior in seawater ion complexes

Zhu

Doherty

et al. 2013

Microporous and Mesoporous Materials

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“…Figure 1(b) shows a SEM image of a spin-on PSZ MEL film (type 5) consisting of MEL nanoparticles embedded in a nonuniform, disordered, and porous silica matrix along with an inset showing the MEL framework viewed down the a-axis [18]. In addition, unlike the MFI thin film, the MEL thin films featured also a mesoporosity corresponding to the volume fraction occupied by mesopores 2.3 to 2.6 nm in diameter [21]. These mesopores were located between the disordered silica matrix and the MEL nanoparticles [22].…”

Section: Figurementioning

confidence: 99%

Temperature dependent thermal conductivity of pure silica MEL and MFI zeolite thin films

Fang

Huang

Lew

et al. 2012

Journal of Applied Physics

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Several studies have reported the thermal conductivity of powdered zeolites [12][13][14][15]. Effects of temperature, filling gas, moisture, and pressure were investigated [12][13][14][15]. In addition, Greenstein et al. [16] and Hudiono et al. [17] measured thermal conductivity of PSZ MFI zeolite films with thickness ranging from 10 to 20 µm and temperature varying from 150 to 450 K. The MFI films were synthesized by secondary growth through a seeded hydrothermal process on alumina substrates. The measured thermal conductivity of (h0l)-oriented PSZ MFI films varied from 1.0 to 1.4 W/m·K in the temperature range considered [17]. That of calcined and uncalcined c-oriented PSZ MFI films deposited on silicon substrates was found to range from 0.75 to 1.1 W/m·K and 1.0 to 1.6 W/m·K, respectively [16]. More recently, Coquil et al. [18] measured room temperature thermal conductivity of PSZ MFI and MEL zeolite thin films. The MFI thin films were b-oriented, fully crystalline, and had a porosity of 33%. The MEL thin films featured porosity, relative crystallinity, and particle size ranging from 40% to 59%, 23% to 47%, and 55 to 80 nm, respectively. The authors found the thermal conductivity to be around 1.02±0.10 W/m·K for all films despite their different porosity, relative crystallinity, and nanoparticle size. Methods and Experiments 2.1 Sample film preparationSynthesis of PSZ MFI and MEL thin films investigated in the present study were previously described in detail [1,6,18]. MFI thin films were synthesized by in situ crystallization and were b-oriented. The MEL films were prepared by spin coating a zeolite nanoparticle suspension onto silicon substrates. The MEL suspension was synthesized by a two-stage process [1]. The first stage consisted of a 2 days heating and stirring of a tetraethylorthosilicate (TEOS) based solution at 80 • C resulting in a MEL nanoparticle suspension. The second stage corresponded to the growth of the MEL nanoparticles from the same solution in a convection oven at 114 • C. Finally, MEL thin films were obtained by spin-coating the solution onto silicon substrates. Both relative crystallinity and nanoparticle size of the PSZ MEL increased as the second stage synthesis time increased. Here, the relative crystallinity is defined as the ratio of the micropore volume to the micropore volume of a fully crystalline PSZ MEL microcrystal [1]. Four different sets of MEL films corresponding to four different second stage synthesis times (15, 18, 21 and 24 hours) were studied. Note that all the MEL and MFI thin films were made hydrophobic by vapor-phase silylation with trimethylchlorosilane as described in Ref. [1].

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“…We are presently working with IMEC to compare EP results with PALS for pure silica zeolite films. PALS has demonstrated resolution to its 0.55 nm diameter oriented channels [10] but EP may not be detecting them for lack of toluene penetration. Overall, the universal PALS pore size calibration appears to be very reliable but, as we are beginning to now hear at this conference, experiments are searching for a material specific dependence.…”

mentioning

confidence: 99%

Future directions of positron annihilation spectroscopy in low‐k dielectric films

Gidley

Vallery

Liu

et al. 2007

Phys. Status Solidi (c)

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. 55.+f, 78.55.Mb, 78.70.Bj Positronium Annihilation Lifetime Spectroscopy (PALS) has become recognized in the microelectronics industry as one of only several methods capable of quantitatively characterizing engineered nanopores in next-generation (k < 2.2) interlayer dielectric (ILD) thin films. Successes and shortcomings of PALS to date will be assessed and compared with other methods of porosimetry such as ellipsometric and X-ray porosimetries (EP and XRP). A major theme in future low-k research focuses on the ability to integrate porous ILD's into chip fabrication; the vulnerability of porous dielectrics to etching, ashing, and chemical-mechanical polishing in process integration is delaying the introduction of ultra-low-k films. As device size approaches 45 nm the need to probe very small (sub-nanometer), semi-isolated pores beneath thin diffusion barriers is even more challenging. Depth-profiled PALS with its ability to determine a quantitative pore interconnection length and easily resolve 0.3 nm pores beneath diffusion barriers or in trench-patterned dielectrics should have a bright future in porous ILD research. The ability of PALS (and PAS in general) to deduce evolution and growth of pores with porosity should find broad applicability in the emerging field of high performance materials with strategically engineered nanopores.

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Evaluation of Pore Structure in Pure Silica Zeolite MFI Low-k Thin Films Using Positronium Annihilation Lifetime Spectroscopy

Cited by 57 publications

References 24 publications

Designing hierarchical porous features of ZSM-5 zeolites via Si/Al ratio and their dynamic behavior in seawater ion complexes

Designing hierarchical porous features of ZSM-5 zeolites via Si/Al ratio and their dynamic behavior in seawater ion complexes

Temperature dependent thermal conductivity of pure silica MEL and MFI zeolite thin films

Future directions of positron annihilation spectroscopy in low‐k dielectric films

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