Analytical optoacoustic spectrometry. Part III. The optoacoustic effect and thermal diffusivity

Adams, M. J.; Kirkbright, G. F.

doi:10.1039/an9770200281

Cited by 177 publications

(44 citation statements)

References 3 publications

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“…S o = tan-l(S90/S0) or S o = v -tan-l(S9o/So) (5) where the first applies when $45 > S~35 and the latter applies when $45 < S135. Figure 5 shows the phase and power spectra at 400-Hz phase modulation for the 6-~xm PET on polycarbonate sample.…”

Section: And Discussionmentioning

confidence: 99%

Quantitative Depth Profiling of Layered Samples Using Phase-Modulation FT-IR Photoacoustic Spectroscopy

Jones

McClelland

1996

Appl Spectrosc

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In phase-modulation FT-IR spectroscopy, all wavelengths in a spectrum are modulated at the same frequency and in phase. This factor makes the use of photoacoustic phase data for depth profiling samples much easier in phase modulation than in rapid scan. A method to quantitatively measure layer thickness by using the phase of a substrate spectrum peak is demonstrated with a series of samples consisting of thin polymer films on substrates. Additions to the basic method are demonstrated that extend its application to cases where the substrate peak is overlapped by a spectrum peak of the surface film. A linear relationship between phase angle and layer thickness extending to thicknesses greater than twice the thermal diffusion length is demonstrated. Representations of phase modulation data as a family of angle-specific spectra, as magnitude vs. phase curves, and as a power spectrum and phase spectrum pair, each of which is useful for different aspects of depth profiling, are discussed. Calculating these representations from a single pair of orthogonal interferograms is described. In phase-modulation FT-IR spectroscopy, all wavelengths in a spectrum are modulated at the same frequency and in phase. This factor makes the use of photoacoustic phase data for depth profiling samples much easier in phase modulation than in rapid scan. A method to quantitatively measure layer thickness by using the phase of a substrate spectrum peak is demonstrated with a series of samples consisting of thin polymer films on substrates. Additions to the basic method are demonstrated that extend its application to cases where the substrate peak is overlapped by a spectrum peak of the surface film. A linear relationship between phase angle and layer thickness extending to thicknesses greater than twice the thermal diffusion length is demonstrated. Representations of phase modulation data as a family of angle-specific spectra, as magnitude vs. phase curves, and as a power spectrum and phase spectrum pair, each of which is useful for different aspects of depth profiling, are discussed. Calculating these representations from a single pair of orthogonal interferograms is described. Keywords

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Section: And Discussionmentioning

confidence: 99%

Quantitative Depth Profiling of Layered Samples Using Phase-Modulation FT-IR Photoacoustic Spectroscopy

Jones

McClelland

1996

Appl Spectrosc

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“…[2][3][4][5][6][7][8][9][10][11][12][13][14] In this work, we have extended the use of photoacoustic spectroscopy as a novel means of studying a non-repetitive dynamic system. The system studied consisted of a hydrocarbon grease diffusing through a porous Teflon film.…”

Section: Introductionmentioning

confidence: 99%

Observation of Large Photoacoustic Signal Phase Changes during a Diffusion Process

2005

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The phase of the photoacoustic signal is known to be a sensitive and accurate means to investigate, both qualitatively and quantitatively, static multilayer heterogeneous systems. According to theory, the maximum phase delay for a very weakly absorbing homogeneous sample should be within 45° of a very strongly absorbing sample, while for heterogeneous samples the phase delay can be greater than 45°. Here we report the observation of photoacoustic phase delays greater than 350°by extending the use of step-scan phase modulation photoacoustic spectroscopy to study a non-repetitive dynamic system in situ, in real time. These large phase delays correspond to sampling several thermal diffusion lengths into the sample. The model system used in this study consisted of a hydrocarbon grease diffusing through a porous Teflon film. The progress of the diffusion was tracked by monitoring both the photoacoustic signal magnitude and the phase of the hydrocarbon grease after isolation from the Teflon film signal contributions at two different phase modulation frequencies. The phase of the photoacoustic signal is known to be a sensitive and accurate means to investigate, both qualitatively and quantitatively, static multilayer heterogeneous systems. According to theory, the maximum phase delay for a very weakly absorbing homogeneous sample should be within 45؇ of a very strongly absorbing sample, while for heterogeneous samples the phase delay can be greater than 45؇. Here we report the observation of photoacoustic phase delays greater than 350؇ by extending the use of step-scan phase modulation photoacoustic spectroscopy to study a non-repetitive dynamic system in situ, in real time. These large phase delays correspond to sampling several thermal diffusion lengths into the sample. The model system used in this study consisted of a hydrocarbon grease diffusing through a porous Teflon film. The progress of the diffusion was tracked by monitoring both the photoacoustic signal magnitude and the phase of the hydrocarbon grease after isolation from the Teflon film signal contributions at two different phase modulation frequencies. Keywords

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“…A simple apparatus was described in the studies of Asams and Kirkbright [1,2] that permitted heat-flow characteristics of a sample to be determined, and its application of the thermal diffusivity or thickness of polymer films on a copper substrate was reported. The amplitude and phase of observed optoacoustic signal depend on the thermal diffusivity and thickness of the material irradiated.…”

Section: Introductionmentioning

confidence: 99%

The measuring technique developed to evaluate the thermal diffusivity of the multi-layered thin film specimens

Lin

2017

MATEC Web Conf.

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Abstract. In the present study, the thermal diffusivities of the Al, Si and ITO films deposited on the SUS304 steel substrate are evaluated via the present technique. Before applying this technique, the temperature for the thin film of the multi-layered specimen is developed theoretically for the onedimensional steady heat conduction in response to amplitude and frequency of the periodically oscillating temperature imposed by a peltier placed beneath the specimen's substrate. By the thermal-electrical data processing system excluding the lock-in amplifier, the temperature frequency a 3 has been proved first to be independent of the electrical voltage applied to the peltier and the contact position of the thermocouples. The experimental data of phase difference for three kinds of specimen are regressed well by a straight line with a slope. Then, the thermal diffusivity of the thin film is thus determined if the slope value and the filmthickness are available. In the present arrangements for the thermocouples, two thermal diffusivity values are quite close each other and valid for every kind of specimen. This technique can provide an efficient, low-cost method for the thermal diffusivity measurements of thin films.

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Analytical optoacoustic spectrometry. Part III. The optoacoustic effect and thermal diffusivity

Cited by 177 publications

References 3 publications

Quantitative Depth Profiling of Layered Samples Using Phase-Modulation FT-IR Photoacoustic Spectroscopy

Quantitative Depth Profiling of Layered Samples Using Phase-Modulation FT-IR Photoacoustic Spectroscopy

Observation of Large Photoacoustic Signal Phase Changes during a Diffusion Process

The measuring technique developed to evaluate the thermal diffusivity of the multi-layered thin film specimens

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