Photoacoustic Spectroscopy Theory for Multi-Layered Samples and Interference Effect

Fujii, Yasuhiro; Moritani, Akihiro; Nakai, Junkichi

doi:10.1143/jjap.20.361

Cited by 67 publications

(13 citation statements)

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“…Here we assume incident light of intensity I 0 suffers reflection R at the interface besides R s at the front surface and r at the internal surface. We extend the theoretical treatment of Helander [2] to the case of the two-layer structure [11] including a term describing the effect of reflection R [12]. Although increased roughness in sample B might affect the effective scattering coefficient β s or effective thickness l which could enhance the PA signals, we focused our attention on the effect of R. Also, for simplicity, we assume a relation β a = (1 − p)β 2a , where p is the porosity, and β a , β 2a are absorption coefficients of the PS layer and the substrate, respectively.…”

Section: Resultsmentioning

confidence: 99%

Effects of boundary reflection on photoacoustic spectrum of porous silicon

Kawahara

Morimoto

Tahira

et al. 2000

Applied Physics A: Materials Science & Processing

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Photoacoustic (PA) amplitude and phase spectra are studied on porous silicon (PS) samples. For the sample with a thinner PS layer and a rough interface observed by field-emission scanning electron microscope (FE-SEM), PA amplitude decays rapidly at short wavelengths but stays at a higher level above 650 nm compared with a sample with a thicker PS layer and a smooth interface. In this latter longwavelength region, phase delay for the former sample is smaller. A model calculation for the two-layer model taking account of scattering of light in the porous media and interface reflection of light gives at least a qualitative explanation of these differences. 78.20.Hp; 65.90.+i Photoacoustic spectroscopy (PAS) detects the thermal signals generated in materials under light illumination and enables one to study the non-radiative recombination processes and evaluate both the optical and acoustic properties of the materials [1]. In contrast, photoluminescence (PL) spectroscopy characterizes the luminescent properties from the radiative processes. When these methods are applied to the scattering media, the analysis based on some models regarding the effect of scattering is required. In the case of PAS in the lightscattering media, Helander's model [2] can be employed in which the modified distribution of photons in the media is taken into account to estimate the heat generated by the scattered light. The light-scattering is expected to be important in the porous media. The complicated shape of pores can induce the complicated scattering of light in the media. PACS:The light emission of porous Si (PS) was discovered in 1990 [3]. The efficient visible-light emission in red was reported first, but the blue emission was reported to be related to the oxidized PS samples [4,5] and gave a promise for the Si-based optical devices. Although PL spectra were reported for PS [3,6], no careful analysis on the effect of scattering seems to have been considered and only a few photoacoustic (PA) measurements are reported in the PS samples [7,8]. The nano-structure that is expected to lead to the quantum confinement effect [9], believed to be essential for the light emission from PS, will also play a decisive role in the scattering effect.In this paper, both amplitude and phase PA signals are studied over a wavelength region 400-1600 nm on the two PS samples with different interface characteristics between the porous layer and the Si substrate. The difference in PA spectra is attributed to the combined effect of the scattering in the porous layer and the difference in roughness observed from the scanning electron microscope pictures of the interface between the PS layer and the Si substrate. The experimental PA data are qualitatively analyzed based on the calculated PA spectra in which the reflection effects of light at the interface and the subsequent scattering are included. Experimental proceduresThe PS films were made by the anodization of the 2-4 Ω cm p-Si wafers under galvanostatic conditions. The Si wafer was also used as one elec...

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Section: Resultsmentioning

confidence: 99%

Effects of boundary reflection on photoacoustic spectrum of porous silicon

Kawahara

Morimoto

Tahira

et al. 2000

Applied Physics A: Materials Science & Processing

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“…In the above expression E and H are the electric and the magnetic vector magnitudes, Re means that the real part of the expression in the square brackets is taken, * denotes complex conjugation, and c is a constant factor depending on the metric system used. The expression P z EE* used in [12] is not valid for an absorbing medium in the case of light interference.…”

Section: Thermal Wave Generationmentioning

confidence: 99%

Interference Analysis of Photothermal Generation of Waves in Layered Structures

Velinov

Bransalov

1990

phys. stat. sol. (a)

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The role of the interference of the optical, thermal, and elastic waves in the case of optical generation of thermal and elastic fields in layered media is described. The one‐dimensional case is considered. The influence of the optical, thermal, elastic, and thermoelastic parameters as well as the thickness of the absorbing layer on the temperature and the amplitude of the ultrasonic waves is emphasized.

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“…4 A PA theory for double layers was also derived by Fujii et al 5 They extended their model for a multilayer as well. Baumann 6,7 had reported an evaluation of the exact solution for a triple-layered polymer film, and Brunn 8 extended the model by including the effects of optical interference.…”

Section: Introductionmentioning

confidence: 99%

Fourier transform infrared photoacoustic spectroscopy of polymeric laminates

Wahls

Leyte

1998

Journal of Applied Physics

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Photoacoustic Fourier transform infrared spectroscopy of nanoporous SiO x ∕ Si thin films with varying porosities J. Appl. Phys. 98, 114310 (2005); 10.1063/1.2138376 X-ray photoemission spectroscopy and Fourier transform infrared studies of dye molecule doped conducting polymer films J. Vac. Sci. Technol. A 23, 869 (2005); 10.1116/1.1914816The (n00), n=3, 4, and 6, local mode states of H 3 SiD : Fourier transform infrared and laser photoacoustic spectra and ab initio calculations of spectroscopic parameters Photoacoustic ͑PA͒ magnitude and phase spectra of, respectively, polyethyleneterephthalate/ polyethyleneterephthalate ͑PET/PET͒, polypropylene/polyethyleneterephthalate ͑PP/PET͒, and polyethyleneterephthalate/polypropylene ͑PET/PP͒ laminates are presented. The extension of the Rosencwaig-Gersho theory to a double-layered system introduced by N. C. Fernelius ͓J. Opt. Soc. Am. 70, 480 ͑1980͒ and J. Appl. Phys. 51, 650 ͑1980͔͒ is applied to compare the experimental data with simulated PA magnitudes and phases. The simulations for the double-layered systems indicate that the absorption coefficient ␤ at the optically transparent region of the single layers-estimated from photoacoustic data-strongly influences the phase spectra of the polymeric laminate. In particular, the relative magnitude of these residual absorptions in the two layers is important. The optical absorption spectra of the polypropylene and polyethyleneterephthalate single layers ͑accessible from infrared absorbance and infrared photoacoustic spectra͒ were used to simulate the photoacoustic magnitude and phase spectra of the two possible double layers, i.e., PP/PET and PET/PP. A reasonable agreement of experimental and simulated photoacoustic data is observed.

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Photoacoustic Spectroscopy Theory for Multi-Layered Samples and Interference Effect

Cited by 67 publications

References 11 publications

Effects of boundary reflection on photoacoustic spectrum of porous silicon

Effects of boundary reflection on photoacoustic spectrum of porous silicon

Interference Analysis of Photothermal Generation of Waves in Layered Structures

Fourier transform infrared photoacoustic spectroscopy of polymeric laminates

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