Temperature distribution in a film heated with a laser spot: Theory and measurement

Emmerich, Rudolf; Bauer, Siegfried; Ploss, B.

doi:10.1007/bf00324197

Cited by 18 publications

(7 citation statements)

References 14 publications

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“…When the size of the heated spot is much larger than the sample thickness d, a onedimensional solution T (z, t) is usually sufficient [17]. The validity of this assumption in the present case will be discussed in Sect.…”

Section: Theory and Data Processingmentioning

confidence: 95%

Thermal-Pulse Tomography of Space-charge and Polarization Distributions in Electret Polymers

et al. 2008

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A new, non-destructive technique for the analysis of electret materials is presented. Thermal-pulse tomography produces three-dimensional images of spacecharge and polarization distributions with a lateral resolution of better than 50 µm and a depth resolution of less than 0.5 µm. A focused-pulsed laser heats a circular spot on the opaque upper electrode. While diffusing through the sample, the thermal pulse causes local changes in the sample geometry or dielectric properties, resulting in a short-circuit current in the presence of space charge or electric dipoles. From the transient current, the distribution of the internal electric field can be reconstructed by means of scale transformation or regularization methods.

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Section: Theory and Data Processingmentioning

confidence: 95%

Thermal-Pulse Tomography of Space-charge and Polarization Distributions in Electret Polymers

et al. 2008

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“…Previous LIMM or thermal-pulse experiments used a onedimensional solution. 26,27 For polymer films with evaporated metal electrodes, only the polymer itself needed to be considered, as the electrodes are usually 2-3 orders of magnitude thinner than the polymer film. For a tightly focused laser beam, however, lateral diffusion in the electrode becomes important.…”

Section: B Temperature Distribution and Pyroelectric Profilementioning

confidence: 99%

Resolution-enhanced polarization imaging with focused thermal pulses

Aryal

Mellinger

2013

Journal of Applied Physics

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The non-destructive measurement of electrical polarization and space charge densities is a key technique in electret research. The principal idea behind these methods is a non-uniform deformation or heating, which gives rise to a short-circuit current that can be recorded in the time or frequency domain, and which carries information about the polarization depth profile. In recent years, thermal pulses and thermal waves have been used successfully to obtain three-dimensional polarization maps in polymeric electrets by scanning the beam of a pulsed or intensity-modulated cw laser across the sample surface. However, the polarization maps in these experiments were reconstructed using a relatively simplistic one-dimensional heat diffusion model that does not take into account lateral heat diffusion in the metal electrode. A two-dimensional “coupled neighbors” model was developed, where the current signal from several adjacent beam pointings along a scan line is coupled together, and a Monte Carlo method is used for the deconvolution. Simulations show that the new approach enhances the lateral resolution by a factor of 2−3×, since it avoids the information loss occurring when three-dimensional polarization measurements are processed with a one-dimensional thermal model. We also present an augmented, low-noise thermal-pulse instrument where thermal pulses are initiated by a pulse-modulated diode laser.

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“…Photothermal measurements mostly engage in the determination of the amplitude or phase of a periodically varying thermal wave, induced by harmonically modulated lasers on the sample surface. A range of photothermal effects is utilized among which pyroelectric detection, 9 interferometry, 10 thermoreflectance, 11 mirage effect 12 and radiometry, 13 to name a few, were individually studied. In order to address the problem of heat flow in a layered structure one has to take into account the effect of interfaces and thin layers since they lead to reflection of heat waves and thermal wave interference.…”

Section: Introductionmentioning

confidence: 99%

Bonding characterization, density measurement, and thermal diffusivity studies of amorphous silicon carbon nitride and boron carbon nitride thin films

Chattopadhyay

Chen

Chien

et al. 2002

Journal of Applied Physics

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Thermal diffusivity (α) of amorphous silicon carbon nitride (a-SiCxNy) and boron carbon nitride (a-BCxNy) thin films on crystalline silicon has been studied as a function of the carbon content and thickness of the films using the traveling wave technique. The thermal diffusivity showed a steady fall from ∼0.35 to about 0.15 cm2/s for a-SiCxNy films as the carbon content increased from 30 to ∼70 at. %. This decrease in thermal diffusivity was also accompanied by a decrease in the film density from 3.35 to ∼2.3 g/cm3 as a function of the carbon content of the a-SiCxNy films. In case of a-BCxNy, a peak in thermal diffusivity (0.6 cm2/s) was detected at a carbon concentration of ∼25 at. % which reduced to 0.2 cm2/s for a carbon concentration of ∼60 at. % in the films. The value of the density also showed a peak (∼2 g/cm3) at a carbon concentration of 25 at. % before decreasing in the a-BCxNy films. A study of bonding characterization revealed a dominant lower coordinated C(sp)–N phase at higher carbon concentrations that played a detrimental role in the film properties observed. A critical issue of the thickness dependence of thermal diffusivity in a layered structure of a-SiCxNy and a-BCxNy on silicon is addressed with information extracted from aluminum thin films on different substrates. An empirical model is proposed which can explain the reported thickness and substrate dependence of the thermal diffusivity data.

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Temperature distribution in a film heated with a laser spot: Theory and measurement

Cited by 18 publications

References 14 publications

Thermal-Pulse Tomography of Space-charge and Polarization Distributions in Electret Polymers

Thermal-Pulse Tomography of Space-charge and Polarization Distributions in Electret Polymers

Resolution-enhanced polarization imaging with focused thermal pulses

Bonding characterization, density measurement, and thermal diffusivity studies of amorphous silicon carbon nitride and boron carbon nitride thin films

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