Thermal Expansion-Recovery Microscopy (ThERM) for microstructural characterization

2013 ◽  
Vol 1526 ◽  
Author(s):  
Esteban A. Domené ◽  
Nélida Mingolo ◽  
Oscar E. Martínez
Keyword(s):  
Thermal Expansion ◽  
Thermal Diffusivity ◽  
Probe Beam ◽  
Pump Beam ◽  
Surface Deformation ◽  
Modulation Frequency ◽  
Microstructural Characterization ◽  
Sample Surface ◽  
Beam Size ◽  
Detection Schemes

ABSTRACTIn this work we compare two different detection schemes that are sensitive to the focus shift of a probe beam due to induced surface curvature. The technique on which both detection schemes are based is called ThERM (Thermal Expansion-Recovery Microscopy) and allows the retrieval of the thermal diffusivity at microscopic levels, hence mapping such magnitude over a sample surface. The induced thermal expansion defocuses the probe beam due to the surface deformation (curvature). The dependence of the defocusing with the pump modulation frequency yields the thermal diffusivity of the sample at the impinging location. The explored depth is controlled by the pump beam size. By scanning both beams, a complete map of the thermal diffusivity can be retrieved.

Mirage-effect measurement of thermal diffusivity. Part II: theory

1986 ◽  
Vol 64 (9) ◽  
pp. 1168-1171 ◽  
Author(s):  
P. K. Kuo ◽  
E. D. Sendler ◽  
L. D. Favro ◽  
R. L. Thomas
Keyword(s):  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Probe Beam ◽  
Three Dimensional ◽  
Sample Surface ◽  
Bulk Sample ◽  
Effect Measurement ◽  
Dimensional Theory ◽  
Mirage Effect ◽  
Effect Technique

A three-dimensional theory of a mirage-effect technique for measuring thermal diffusivity of solids is presented. A formula that incorporates sizes and separations of the heating and probe beams; the height of the probe beam above the sample surface; the thermal properties of the sample, the gas, and the backing; and the thickness of the sample is developed. The results are compared with experiments on a bulk sample and on thin slabs of various thicknesses.

New Photothermal Deflection Method to Determine Thermal Properties of Bulk Semiconductors

2010 ◽  
Vol 297-301 ◽  
pp. 525-530
Author(s):  
Imen Gaied ◽  
Salima Lassoued ◽  
Fredéric Genty ◽  
Noureddine Yacoubi
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Modulation Frequency ◽  
Phase Variation ◽  
Sample Surface ◽  
Halogen Lamp ◽  
Bulk Semiconductors ◽  
Photothermal Deflection ◽  
Modulated Light

In this paper, we present a new Photothermal Deflection Technique (PTD) to determine thermal properties of bulk doped or undoped semiconductor such as GaAs, GaSb, InAs, etc. The method proposed here consists in covering the sample with a thin graphite layer in order to increase the photothermal signal and to ovoid any reflection on the sample surface. This method deals with the analysis of the logarithm of amplitude and phase variation of the photothermal signal versus square root modulation frequency where the sample placed in air is heated by a modulated light beam coming from a halogen lamp. So the best coincidence between experimental curves and corresponding theoretical ones gives simultaneously the best values of thermal conductivity and thermal diffusivity of the sample. These obtained values are in good agreement with those found in literature. The advantage of applying this method in this way lies in its simplicity and its sensibility to both thermal conductivity and thermal diffusivity.

Thermal Diffusivity Estimation in a Picosecond Photoreflectance Experiment

2006 ◽  
Vol 129 (6) ◽  
pp. 756-758 ◽  
Author(s):  
Jean-Luc Battaglia ◽  
Andrzej Kusiak ◽  
Jean-Christophe Batsale
Keyword(s):  
Heat Flux ◽  
Thermal Diffusivity ◽  
Impulse Response ◽  
Probe Beam ◽  
Pump Beam ◽  
Asymptotic Behaviors ◽  
Analytical Expression ◽  
Incident Heat Flux ◽  
Average Temperature

The aim of this work is to provide an analytical expression for the thermal diffusivity of a material in the configuration of the picosecond photoreflectance experiment. It is shown that the thermal diffusivity can be estimated from the absorption depth of the pump beam together with the probe beam as well as the time when the two asymptotic behaviors of the impulse response cross. Thereby, it is not required to measure absolute values of incident heat flux and average temperature on the aiming area.

Pump-Probe Measurements Using Silicon Nanocrystal Waveguides

2003 ◽  
Vol 770 ◽  
Author(s):  
Nathanael Smith ◽  
Max J. Lederer ◽  
Marek Samoc ◽  
Barry Luther-Davies ◽  
Robert G. Elliman
Keyword(s):  
Probe Beam ◽  
Time Resolution ◽  
Pump Beam ◽  
Silicon Nanocrystals ◽  
Continuous Wave ◽  
Optical Gain ◽  
Optical Pump ◽  
Time Resolved ◽  
Pump Probe ◽  
Probe Measurements

AbstractOptical pump-probe measurements were performed on planar slab waveguides containing silicon nanocrystals in an attempt to measure optical gain from photo-excited silicon nanocrystals. Two experiments were performed, one with a continuous-wave probe beam and a pulsed pump beam, giving a time resolution of approximately 25 ns, and the other with a pulsed pump and probe beam, giving a time resolution of approximately 10 ps. In both cases the intensity of the probe beam was found to be attenuated by the pump beam, with the attenuation increasing monotonically with increasing pump power. Time-resolved measurements using the first experimental arrangement showed that the probe signal recovered its initial intensity on a time scale of 45-70 μs, a value comparable to the exciton lifetime in Si nanocrystals. These data are shown to be consistent with an induced absorption process such as confined carrier absorption. No evidence for optical gain was observed.

scholarly journals Economical rapid-prototyping of aspherical lenses

2019 ◽  
Vol 215 ◽  
pp. 04001 ◽  
Author(s):  
Angelina Müller ◽  
Matthias C. Wapler ◽  
Ulrike Wallrabe
Keyword(s):  
Thermal Expansion ◽  
Rapid Prototyping ◽  
Shape Optimization ◽  
Surface Deformation ◽  
Fabrication Process ◽  
Aspherical Lens ◽  
Laser Structuring ◽  
Aspherical Lenses ◽  
Design Freedom ◽  
Micro Lens

We present a rapid-prototyping process to fabricate aspherical lens arrays based on surface deformation due to thermal expansion of PDMS. Using laser-structuring and molding in combination with an FEM-based shape optimization, we were able to design, fabricate and characterize different micro-lens arrays. This fabrication process can be used for almost any kind of arbitrary lens shape, which allows for a large design freedom for micro lenses.

Thermal expansion and thermal diffusivity properties of Co-Si solid solutions and intermetallic compounds

2016 ◽  
Vol 102 ◽  
pp. 1-8 ◽  
Author(s):  
Ying Ruan ◽  
Liuhui Li ◽  
Qianqian Gu ◽  
Kai Zhou ◽  
Na Yan ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Thermal Diffusivity ◽  
Intermetallic Compounds ◽  
Solid Solutions

Novel aspects of micro-thermal analysis of polymer blends

1999 ◽  
Vol 5 (S2) ◽  
pp. 980-981
Author(s):  
M. Conroy ◽  
H. M. Pollock ◽  
A. Hammiche ◽  
G. Mills ◽  
J.M.R. Weaver ◽  
...  
Keyword(s):  
Thermal Analysis ◽  
Modulation Frequency ◽  
Sample Surface ◽  
Thermal Image ◽  
Temperature Modulation ◽  
Scanning Thermal Microscopy ◽  
Thermal Probe ◽  
Temperature Ramp ◽  
Temperature Waves ◽  
Chemical Fingerprinting

In “ac” scanning thermal microscopy, an “active” thermal probe is used also as a heater, so as to inject evanescent temperature waves into a sample and to allow sub-surface imaging of polymers and other materials [1]. The sub-surface detail detected corresponds to variations in heat capacity or thermal conductivity. By suitably choosing the temperature modulation frequency, and hence the penetration depth of the wave, we control the depth of material below the sample surface that is contributing to the image.Micro-Thermal Analysis [2, 3] builds upon this technique, in order to add spatial resolution to two well-established methods of chemical fingerprinting, DTA and DMA. In both cases, a temperature ramp is used to subject the sample to “events” such as a glass transition or melting. The chief advantages of using the active thermal probe to provide the temperature ramp as well as the modulation, without the use of a heating stage, are: (a) the data are obtained from localised regions chosen from a previously-obtained thermal image, (b) apart from these regions, the rest of the sample is preserved in its original unheated state.

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