Characterization of thin-film aerogel porosity and stiffness with laser-generated surface acoustic waves

Flannery, C.M.; Murray, Christopher P.; Streiter, I.; Schulz, Stefan E.

doi:10.1016/s0040-6090(01)00827-6

Cited by 49 publications

(23 citation statements)

References 13 publications

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“…As expected, the addition of porosity results in a decrease in SAW velocity. The linear relationship observed is consistent with the work of other researchers [10][11][12].…”

Section: Sic Substrate Characterizationsupporting

confidence: 92%

Measurement and Analysis of Narrow-Band Surface Acoustic Waves in Ceramic Environmental Barrier Coatings

Steen¹,

Basu²,

Sarin³

et al. 2008

AIP Conference Proceedings

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A laser-based ultrasonic system is used to measure the mechanical properties and thickness of mullite environmental barrier coatings deposited on SiC substrates. Narrow-band surface acoustic waves (SAWs) are generated with an amplitude modulated laser source, and a photorefractive crystal based interferometer coupled to a lock-in amplifier is used to detect the resulting surface displacement. The complex displacement field is mapped over a source-to-receiver distance of approximately 500µm in order to extract the wavelength of the SAW at a given excitation frequency, from which the phase velocity is determined. Dispersion curves measured over a frequency range of 100-180MHz are used to extract mean values for the elastic modulus and thickness of the coating over the measurement region. These values are compared to the mean elastic modulus and thickness of the coating measured using nanoindentation and optical microscopy, respectively. It is shown that porosity in the substrate can have a significant impact on the experimental results, particularly over short measurement distances. Experiments on SiC with 1-4% porosity show a linear increase of the mean SAW velocity with decreasing porosity. Additionally, measurements made on a sample with a given bulk porosity indicate that the SAW velocity varies locally, leading to additional error in the measurement of coating properties. This error can be reduced through spatially averaging the velocity measurements.

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“…As expected, the addition of porosity results in a decrease in SAW velocity. The linear relationship observed is consistent with the work of other researchers [10][11][12].…”

Section: Sic Substrate Characterizationsupporting

confidence: 92%

Measurement and Analysis of Narrow-Band Surface Acoustic Waves in Ceramic Environmental Barrier Coatings

Steen¹,

Basu²,

Sarin³

et al. 2008

AIP Conference Proceedings

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“…To further illustrate the unique position of nano-architected materials, Figure 3c compares the hollow alumina nanolattices to several other material systems whose porosity can be varied through processing: hyperbranched poly(amidoamine) conjugated silica (HBPCS) (RD 30-90%), 41 silica xerogel (RD 45-64%), 42 silica aerogel (RD 32-40%), 43 and polyimide aerogel with varying amounts of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 the backbone of the polyimide (0% 6FDA RD 11-16%, 50% 6FDA RD 5.3-8.1%). 28 The dashed contour represents the same scaling as one shown in Figure 3b for nanolattices with relative densities between 1% and 10%.…”

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confidence: 99%

Enabling Simultaneous Extreme Ultra Low-k in Stiff, Resilient, and Thermally Stable Nano-Architected Materials

et al. 2017

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(GIST), Gwangju 61005, Korea † These authors have contributed equally to this work.Keywords: dielectric constant, low-k, nanolattice, porosity, Young's modulus. AbstractLow dielectric constant (low-k) materials have gained increasing popularity because of their critical role in developing faster, smaller, and higher performance devices. Their practical 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 use has been limited by the strong coupling between mechanical, thermal, and electrical properties of materials and their dielectric constant; low-k is usually attained by materials that are very porous, which results in high compliance, i.e. silica aerogels, 39 high dielectric loss, i.e.porous polycrystalline alumina, 25 and poor thermal stability, i.e. Sr-based metal-organic frameworks. 23 We report the fabrication of 3D nano-architected hollow-beam alumina dielectrics whose k is 1.06-1.10 at 1MHz that is stable over the voltage range of -20V to 20V and a frequency range of 100 kHz to 10 MHz. This dielectric material can be used in capacitors and is mechanically resilient, with a Young's modulus of 30 MPa, a yield strength of 1.07 MPa, a nearly full shape recoverability to its original size after >50% compressions, and outstanding thermal stability with a thermal coefficient of dielectric constant (TCK) of 2.43 × 10 -5 K -1 up to 800 °C. These results suggest that nano-architected materials may serve as viable candidates for ultra low-k materials that are simultaneously mechanically-resilient, and thermally and electrically stable for microelectronics and devices. Main TextDesigning and synthesizing low dielectric constant (low-k) materials has been a subject of intense research because of their potential use in high performance technological applications like computer processing, 1,2 wireless communications, [3][4][5][6] and automotive radar. 7 Lowering the k of the interlayer dielectric decreases the resistance-capacitance (RC) delay, lowers power consumption, and reduces cross-talk between nearby interconnects, all of which pose significant issues for modern integrated circuits (ICs). [8][9][10] The low-k property is also favored in low temperature co-fired ceramic (LTCC) technology and represents the backbone of Multi Chip Module (MCM) technology, which enables the integration of passive elements like inductors, 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 3 resistors, and capacitors, which serve as building blocks for 3D circuits for the microwave/millimeter communications industry. [11][12] For example, the antenna in a typical RF module for radiating/receiving radio waves, requires the supporting substrate whose k is sufficiently low to preven...

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“…Due to the limited size of the effectively tested material volume, the local pore structure may seriously affect indentation test results (Vanstreels et al, 2013). Advanced optical or acoustic tests, which are used to determine Poisson's ratio, depend upon accurate density measurements and a detailed analysis of the test data to yield reliable results (Flannery et al, 2001;Zhou et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Homogenisation of porous thin films and perforated layers: Comparison of analytical and numerical approaches

Richter

2015

Mechanics of Materials

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Keywords:Finite element method Self-consistent method Mori-Tanaka approach Micromechanics Porous thin films Constitutive behaviour a b s t r a c tThe mechanical properties of porous thin films and perforated layers are affected by pore content, shape and arrangement. The experimental determination of the in-plane mechanical properties of such materials is challenging, yet reliable data are essential for materials development and component design. Analytical and numerical approaches therefore provide valuable, supplementary tools for evaluating the effect of porosity on the mechanical properties of such materials.The applicability of both the classical self-consistent method and the Mori-Tanaka approach to the estimation of the effective elastic properties of porous thin films and perforated layers is investigated in this paper. For generic model microstructures with various arrangements of pores, variable pore content and varying matrix Poisson's ratio, the effective elastic properties predicted by the classical self-consistent method and by the Mori-Tanaka approach are quantitatively compared with results obtained by numerical experiments. Based upon this comparison, the range of validity of both the classical self-consistent method and the Mori-Tanaka approach with regard to the different arrangements of pores investigated is defined, and the deviation to be expected if critical values of pore content or inter-pore distance are exceeded and interactions between adjacent pores are occurring is assessed.

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Characterization of thin-film aerogel porosity and stiffness with laser-generated surface acoustic waves

Cited by 49 publications

References 13 publications

Measurement and Analysis of Narrow-Band Surface Acoustic Waves in Ceramic Environmental Barrier Coatings

Measurement and Analysis of Narrow-Band Surface Acoustic Waves in Ceramic Environmental Barrier Coatings

Enabling Simultaneous Extreme Ultra Low-k in Stiff, Resilient, and Thermally Stable Nano-Architected Materials

Homogenisation of porous thin films and perforated layers: Comparison of analytical and numerical approaches

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