Impulse Photothermal Evaluation of Materials Via Frequency Modulated Optical Reflectance II: Experimental

Recently, a powerful method of photothermal detection was reported which enabled thermal wave imaging to be carried out on micron sized structures in semiconductors [1,2]. The new method utilized the photothermally induced modulation of the sample’s surface optical reflectivity to detect thermal wave phenomena at bandwidths exceeding 10 MHz. The wide bandwidth capabilities of the method enabled very shallow structures to be analyzed in semiconducting materials because of the relationship that exists between the modulation frequency of the excitation beam and the thermal diffusion length

Electron and Phonon Thermal Waves in Semiconductors: an Application to Photothermal Effects

The electron and phonon temperature distribution function are calculated in semiconductors. We solved the coupled one-dimensional heat-diffussion equations in the linear approximation in which the physical parameters on the sample are independent of the temperature. We also consider the heat flux at the surface of the semiconductor as a boundary condition for each electron and phonon systems instead of using a fixed temperature. From this, we obtain an expression for electron and phonon temperature respectively. The characterization of the thermal waves properties is duscussed and some practical procedures for this purpose provide us information about the electron and phonon thermal parameters.Comment: 12 pages, amstex and amssymb macro package (LaTeX2e edition

Thermal Diffusion of a Two Layer System

In this paper thermal conductivity and thermal diffusivity of a two layer system is examined from the theoretical point of view. We use the one dimensional heat diffusion equation with the appropriate solution in each layer and boundary conditions at the interfaces to calculate the heat transport in this bounded system. We also consider the heat flux at the surface of the samle as boundary condition instead of using a fixed tempertaure. From this, we obtain an expression for the efective thermal diffusivity of the composite sample in terms of the thermal diffusivity of its constituent materials whithout any approximations.Comment: 16 pages, 1 figure, RevTeX v. 3.0 macro packag

Buried Thermoplastic Layer Diagnostics by the Use of Photo-Thermo-Acoustic Radiometry

Nondestructive evaluation of buried layers finds important applications in industry. In this paper we describe a fast, non-contact photothermal technique for thermoacoustic characterization of a thermoplastic layer sandwiched between two metal foils used in heat sealed food containers. For this particular application a non-contact measurement was required of the thickness of the polymer layer between two layers of aluminum in a heat sealed container rim at a speed of four locations of the container in 60 sec

Thermal diffusivity, effusivity and conductivity of CdMnTe mixed crystals

Cd1-xMnxTe mixed crystals belong to a class of materials called ‘‘semimagnetic semiconductor’’ or diluted magnetic semiconductor (DMS) with addition of magnetic ions like Mn2+ implemented into crystal structure. The crystals under investigation were grown from the melt by the high pressure high temperature modified Bridgman method in the range of composition 0 < x < 0.7. Thermal properties of these compounds have been investigated by means of photopyroelectric (PPE) calorimetry in both, back and front detection configuration. The values of the thermal diffusivity and effusivity were derived from experimental data. Thermal conductivity of the specimens was calculated from the simple theoretical dependencies between thermal parameters. The influence of Mn concentration on thermal properties of Cd1-xMnxTe crystals have been presented and discussed