Characterizing Porosity in Nanoporous Thin Films Using Positronium Annihilation Lifetime Spectroscopy

AbstractDepth profiled positronium annihilation lifetime spectroscopy (PALS) has been used to probe the pore characteristics (size, distribution, and interconnectivity) in thin, porous films, including silica, organic and hybrid films. PALS has good sensitivity to and resolution of all pores (both interconnected and closed) in the size range from 0.3 nm to 30 nm, even in films buried under a diffusion barrier. In this technique a focussed beam of several keV positrons forms positronium (Ps, the electron-positron bound state) with a depth distribution that depends on the selected positron beam energy. Ps inherently localizes in the pores where its natural (vacuum) annihilation lifetime of 142 ns is reduced by collisions with the pore surfaces. The collisionally reduced Ps lifetime is correlated with pore size and is the key feature in transforming a Ps lifetime distribution into a pore size distribution. In hybrid films made porous by a degradable porogen PALS readily detects a percolation threshold with increasing porosity that represents the transition from closed pores to interconnected pores. PALS is a non-destructive, depth profiling technique with the only requirement that positrons can be implanted into the porous film where Ps can form.

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Probing Pore Characteristics in Low-K Thin Films Using Positronium Annihilation Lifetime Spectroscopy

MRS Proceedings ◽

10.1557/proc-612-d4.3.1 ◽

2000 ◽

Vol 612 ◽

Cited By ~ 8

Author(s):

D. W. Gidley ◽

W. E. Frieze ◽

T. L. Dull ◽

J. N. Sun ◽

A. F. Yee

Keyword(s):

Pore Size Distribution ◽

Pore Size ◽

Size Distribution ◽

Average Pore Size ◽

Gas Absorption ◽

Porous Films ◽

Pore Characteristics ◽

Average Pore ◽

Positronium Annihilation ◽

Positronium Annihilation Lifetime Spectroscopy

AbstractDepth profiled positronium annihilation lifetime spectroscopy (PALS) has been used to probe the pore characteristics (size, distribution, and interconnectivity) in thin, porous films, including silica and organic-based films. The technique is sensitive to all pores (both interconnected and closed) in the size range from 0.3 nm to 300 nm, even in films buried under a diffusion barrier. PALS may be particularly useful in deducing the pore-size distribution in closed-pore systems where gas absorption methods are not available. In this technique a focussed beam of several keV positrons forms positronium (Ps, the electron-positron bound state) with a depth distribution that depends on the selected positron beam energy. Ps inherently localizes in the pores where its natural (vacuum) annihilation lifetime of 142 ns is reduced by collisions with the pore surfaces. The collisionally reduced Ps lifetime is correlated with pore size and is the key feature in transforming a Ps lifetime distribution into a pore size distribution. In thin silica films that have been made porous by a variety of methods the pores are found to be interconnected and an average pore size is determined. In a mesoporous methyl-silsesquioxane film with nominally closed pores a pore size distribution has been determined. The sensitivity of PALS to metal overlayer interdiffusion is demonstrated. PALS is a non-destructive, depth profiling technique with the only requirement that positrons can be implanted into the porous film where Ps can form.

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Electrical, Mechanical, and Structural Properties of Fluoro-Containing Poly(silsesquioxanes) Based Porous Low k Thin Films

MRS Proceedings ◽

10.1557/proc-766-e8.3 ◽

2003 ◽

Vol 766 ◽

Author(s):

Jingyu Hyeon-Lee ◽

Jihoon Rhee ◽

Jungbae Kim ◽

Jin-Heong Yim ◽

Seok Chang

Keyword(s):

Thin Films ◽

Pore Size ◽

Dielectric Constants ◽

Commercial Application ◽

Porous Films ◽

Low Dielectric ◽

Nanoporous Films ◽

Positronium Annihilation ◽

Positronium Annihilation Lifetime Spectroscopy ◽

Low K

AbstractLow dielectric fluoro-containing poly(silsesquioxanes) (PSSQs) have been synthesized using trifluoropropyl trimethoxysilane (TFPTMS), methyl trimethoxysilane (MTMS), and 2, 4, 6, 8-tetramethyl-2, 4, 6, 8-tetra(trimethoxysilylethyl) cyclotetrasiloxane. The properties of fluorocontaining PSSQs based thin films were studied by electrical, mechanical, and structural characterization. Film was spun on a silicon substrate, baked at 150°C and 250°C for 1 minute, respectively, and cured in the furnace at 420°C for 1 hour under vacuum condition. Thermally decomposable trifluoropropyl groups of the fluoro-containing PSSQ were served as a pore generator and partially contributed to lower a dielectric constant. â-cyclodextrin (CD) was also employed as a pore generator. The concentration of the pore generator in the film was varied from 0 to 30 %. The dielectric constants of the porous PSSQ films were found to be in the range of 2.7 – 1.9 (at 100 kHz). Hardness and Young's modulus of the films were measured by nano-indentation. The elastic modulus and hardness of the porous films were well correlated with the concentration of the pore generators. Positronium Annihilation Lifetime Spectroscopy (PALS) was employed to characterize a pore size of the porous fluoro-containing PSSQ film. The pore size of the film was less than 2.2 nm. The nanoporous films showed quite promising properties for commercial application.

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Depth-profiling Pore Morphology in Nanoporous Thin Films Using Positronium Lifetime Annihilation Spectroscopy

MRS Proceedings ◽

10.1557/proc-863-b1.6 ◽

2005 ◽

Vol 863 ◽

Cited By ~ 4

Author(s):

Richard S. Vallery ◽

Hua-Gen Peng ◽

William E. Frieze ◽

David W. Gidley ◽

Darren L. Moore ◽

...

Keyword(s):

Beam Energy ◽

Depth Profiling ◽

Chemical Vapor ◽

Positron Beam ◽

Positronium Lifetime ◽

Implantation Depth ◽

Chemical Vapor Deposited ◽

Positronium Annihilation ◽

Positronium Annihilation Lifetime Spectroscopy

AbstractPositronium annihilation lifetime spectroscopy (PALS) using a positron beam is a proven technique to characterize porosity in amorphous thin film materials. The capability to control the depth of the implanted positrons is unique to beams as compared to traditional bulk PALS techniques. By increasing the positron beam energy, positrons are implanted deeper into the film. Control of the positron implantation depth in beam-PALS allows analysis of sub- micron films, investigation of depth-dependent film inhomogeneities, determination of pore interconnection lengths, and access to buried films under barrier layers. Details on PALS depth profiling and an example of applying the technique to a plasma-enhanced-chemical-vapor- deposited (PECVD) porous film are presented.

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Pore size distribution, their geometry and connectivity in deeply buried Paleogene Es1 sandstone reservoir, Nanpu Sag, East China

Petroleum Science ◽

10.1007/s12182-019-00375-3 ◽

2019 ◽

Vol 16 (5) ◽

pp. 981-1000 ◽

Cited By ~ 3

Author(s):

Muhammad Kashif ◽

Yingchang Cao ◽

Guanghui Yuan ◽

Muhammad Asif ◽

Kamran Javed ◽

...

Keyword(s):

Pore Size ◽

Size Distribution ◽

Coarse Grained ◽

High Porosity ◽

Pore Characteristics ◽

Injection Test ◽

Fine Grained ◽

Mercury Injection ◽

Shahejie Formation ◽

Sandstone Reservoir

Abstract The study of pore characteristics is of great importance in reservoir evaluation, especially in deeply buried sandstone. It controls the storage mechanism and reservoir fluid properties of the permeable horizons. The first member of Eocene Shahejie Formation (Es1) sandstone is classified as feldspathic litharenite and lithic arkose. The present research investigates the pore characteristics and reservoir features of the deeply buried sandstone reservoir of Es1 member of Shahejie Formation. The techniques including thin-section petrography, mercury injection capillary pressure (MICP), scanning electron microscopy and laser scanning confocal microscope images were used to demarcate the pores including primary intergranular pores and secondary intergranular, intragranular, dissolution and fracture pores. Mercury injection test and routine core analysis were led to demarcate the pore network characteristics of the studied reservoir. Pore size and pore throat size distribution are acquired from mercury injection test. Porosity values range from 0.5% to 30%, and permeability ranges 0.006–7000 mD. Pore radii of coarse-grained sandstone and fine-grained sandstone range from 0.2 to > 4 µm and 1 nm to 1.60 µm, respectively, by MICP analysis. The mineral composition also plays an important role in protecting the pores with pressure from failure. Fractured sandstone and coarse-grained sandstone consist of large and interconnected pores that enhance the reservoir porosity and permeability, whereas fine-grained sandstone and siltstone consist of numerous pores but not well interconnected, and so they consist of high porosity with low permeability.

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Depth-profiled positronium annihilation lifetime spectroscopy on porous films

Colloids and Surfaces A Physicochemical and Engineering Aspects ◽

10.1016/j.colsurfa.2006.10.072 ◽

2007 ◽

Vol 300 (1-2) ◽

pp. 154-161 ◽

Cited By ~ 4

Author(s):

Hua-Gen Peng ◽

Richard S. Vallery ◽

Ming Liu ◽

Mark Skalsey ◽

David W. Gidley

Keyword(s):

Porous Films ◽

Positronium Annihilation ◽

Positronium Annihilation Lifetime Spectroscopy

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The nanoscale pore characteristics of coking coals: Part 2 – Optimization of the experimental conditions and calculation methods of pore size distribution

Metallurgical Research & Technology ◽

10.1051/metal/2016053 ◽

2016 ◽

Vol 114 (1) ◽

pp. 116

Author(s):

Huan Cheng ◽

Qi Wang ◽

Song Zhang

Keyword(s):

Pore Size Distribution ◽

Pore Size ◽

Size Distribution ◽

Calculation Methods ◽

Experimental Conditions ◽

Pore Characteristics ◽

Nanoscale Pore

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Stratigraphic and lithofacies control on pore characteristics of Mississippian limestone and chert reservoirs of north-central Oklahoma

Interpretation ◽

10.1190/int-2017-0204.1 ◽

2018 ◽

Vol 6 (4) ◽

pp. T1001-T1022 ◽

Cited By ~ 2

Author(s):

Fnu Suriamin ◽

Matthew J. Pranter

Keyword(s):

Pore Size Distribution ◽

Pore Size ◽

Size Distribution ◽

High Frequency ◽

Reservoir Quality ◽

Pore Characteristics ◽

North Central ◽

Sequence Stratigraphic ◽

Diagenetic Alteration ◽

Mississippian Limestone

We have determined how stratigraphy and lithofacies control pore structures in the Mississippian limestone and chert reservoir of north-central Oklahoma. There are 17 lithofacies and 29 high-frequency cycles documented in the Mississippian interval of this study. The high-frequency cycles have thicknesses ranging from 0.3 to 30.5 m (1–100 ft) and are mainly asymmetric regressive phases. The pore characteristics, measured through digital-image analysis (DIA) of thin-sections photomicrographs ([Formula: see text]100), exhibit unique correlations with core porosity, permeability, and lithofacies within a sequence-stratigraphic framework. There are five fundamental correlations observed. First, porosity from DIA and laboratory core measurements has a strong positive relationship ([Formula: see text]). However, some values from DIA porosity yield relatively higher values, specifically in spiculitic mudstone wackestones and argillaceous spiculitic mudstone wackestones. The difference is hypothesized due to the presence of isolated nanopores that are not accessible by helium during measurement of core porosity. Second, the relationship between pore circularity and permeability is indeterminate. The indeterminate relationship is related to a complex internal pore network, intensive diagenetic alteration, an unconnected microfracture network, and isolated pores. Third, positive moderate to strong correlations ([Formula: see text]) between porosity and permeability are observed only in four lithofacies. Fourth, coarse-grained lithofacies within the uppermost depositional sequence of the Mississippian interval have a heterogeneous pore-size distribution, whereas fine-grained lithofacies tend to exhibit a homogeneous pore-size distribution. Fifth, higher reservoir quality is associated with the upper intervals of high-frequency shallowing-upward cycles. This confirms that the sequence-stratigraphic variability of lithofacies is important to predict reservoir quality and its distribution. An alternative graphical method of pore-size distribution is also developed. To be a useful “technique,” examples of the plot are demonstrated using samples in this study. The plot successfully provides simple identification of pore-size classes, quantitative percentage of pore-size class, dominant pore class, and approximate minimum and maximum pore size.

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Study on 3D Pore Characteristics of Carbon Materials in HTGR by Micro-CT and HPMI Methods

Science and Technology of Nuclear Installations ◽

10.1155/2019/5751463 ◽

2019 ◽

Vol 2019 ◽

pp. 1-10

Author(s):

Shengchao Ma ◽

Zhenzhong Zhang ◽

Kaiyue Shen ◽

Xuedong He ◽

Jun Li ◽

...

Keyword(s):

Pore Size Distribution ◽

Pore Size ◽

Size Distribution ◽

Carbon Materials ◽

Gas Adsorption ◽

Matrix Material ◽

Structure Characteristic ◽

Pore Characteristics ◽

Corrosion Reaction ◽

Special Points

Many tons of porous carbon materials (including BC and IG-110) are contained in HTGR, which are serving as structural material and fuel matrix material. These materials would absorb moisture and other impurities when exposed to the environment, and these impurities (especially moisture) absorbed in the carbon material must be removed before the reactor operation to prevent corrosion reaction at high temperature (more than 500°C). As the pore microscopic structure characteristic is the significant factor affecting the gas adsorption and flow in the porous materials, the detailed 3D pore structures of the carbon materials (BC and IG-110) in HTGR were studied by Micro-XCT and HPMI methods in this paper. These pore structure characteristics include pore geometry, pore size distribution, and pore throat connectivity. The test results show that the pore size distribution of BC material is wide, and the pore diameter is obviously larger than that of IG-110. Pore connections in BC show radial shape connections at some special points, and the pore connectivity in IG-110 is very complex and presents a huge complex 3D pore network.

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Sol-Gel Processing of Low Dielectric Constant Nanoporous Silica Thin Films

MRS Proceedings ◽

10.1557/proc-703-v3.21 ◽

2001 ◽

Vol 703 ◽

Cited By ~ 2

Author(s):

Deok-Yang Kim ◽

Henry Du ◽

Suhas Bhandarkar ◽

David W. Johnson

Keyword(s):

Pore Size Distribution ◽

Pore Size ◽

Size Distribution ◽

Average Pore Size ◽

Sol Gel ◽

Porous Silica ◽

Dielectric Constants ◽

Gelling Agent ◽

Porous Films ◽

Average Pore

ABSTRACTTetramethyl ammonium silicate (TMAS) is known as a structuring agent in zeolite synthesis. We report its first use to prepare porous silica films for low k dielectric applications in microelectronics. A solution of TMAS 18.7 wt. % was spin coated on silicon substrates with a 3000 Å thick thermal oxide. The spin coated films were subsequently heat-treated at 450°C to obtain porous silica. The use of TMAS solution without gelation led to films of only moderate porosity value of 10%. The addition of methyl lactate, a gelling agent, significantly increased film porosity and improved the pore size distribution. For example, 50% porosity and uniform pore size distribution (average pore size ∼ 40 Å) has been achieved. Dielectric constants (k) of our porous films are as low as 2.5.

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