Photothermal Displacement Research Articles

광열변위법의 변형각을 이용한 열확산계수 측정

A new method of measuring the thermal diffusivity of solid material at room temperature using photothermal displacement is proposed. The influence of the parameters, such as radius and modulation frequency of the pump beam and the sample thickness, was studied. In previous works, thermal diffusivity was determined by the deformation angle and phase angle as the relative position between the heating and probe beams. In this study, however, we proposed the new analysis method based on the real part of deformation angle as the relative position between two beams. From the zero-crossing position of real part of deformation angle with respect to the pump beam, the thermal diffusivity of the materials can be obtained. The experimental values for different samples obtained by applying the new method are in good agreement with the literature values.

Measurement of Thermal Diffusivity Using Minimum Phase Based on the Photothermal Displacement

A new method of measuring the thermal diffusivity of solid material at room temperature using photothermal displacement is proposed. The influence of the parameters, such as radius and modulation frequency of the pump beam and the sample thickness, was studied. From the minimum position of phase of measured deflection with respect to the pump beam, the thermal diffusivity of the materials can be obtained. The position where phase has the minimum value is determined using multiparameter least-square regression fitting. The experimental values for different samples obtained by applying the new method are in good agreement with the literature values.

Thermal Diffusivity Measurement for Metal Using Phase Curve of Photothermal Displacement

As the technology has developed and new materials have been produced, it is important to measure the thermal diffusivity of material and to predict the heat transfer in the solid subject to thermal processes. This measurement can be done in a non-contact way using photothermal displacenent spectroscopy. In this study, photothermal displacement method was used to measure the thermal diffusivity quantitatively. The specimens used in this study were the pure materials. The Ar-ion laser was used as an energy source and the periodical deformation induced by this pump laser was detected by the He-Ne laser. The magnitude and the phase angle of deformation gradient were measured. The thermal diffusivity was obtained by analyzing the phase angle of deformation gradient. As the result, comparing with the literature value, the thermal diffusivities of materials measured were showed about 2% error.

A New Noncontact Probe for Thermophysical Properties of Solid Surfaces

Based on the photothermal displacement effect and the optical diffraction effect, an alternative pulsed photothermal technique has been developed. This technique overcomes some disadvantages of conventional methods and provides a sensitive, noncontact and nondestructive probe of the transient thermal and mechanical process at solid and thin film surfaces. Meanwhile, a three-dimensional theoretical model has also been presented to describe the experimental phenomena. Excellent agreement between the theory and the experiment is obtained. As an example, the technique is demonstrated by measuring the thermal diffusivity of aluminum and brass thin plates.

Measurement of thermal diffusivity based on the photothermal displacement technique using the minimum phase method

A method of measuring the thermal diffusivity of solid material at room temperature using photothermal displacement is proposed. The influence of the parameters, such as the radius and modulation frequency of the pump beam and the sample thickness, was studied. From the minimum position of phase of measured deflection with respect to the pump beam, the thermal diffusivity of the materials can be obtained. The position where phase has the minimum value is determined using multiparameter least-square regression fitting. The experimental values for different samples obtained by applying the method are in good agreement with the literature values.

Infrared Spectroscopy with an Atomic Force Microscope

An atomic force microscope (AFM) has been used to measure the modulated photothermal displacement of a surface, thus acting as a local detector. This was demonstrated with Fourier transform infrared (FT-IR) and filter spectrometers focused on various samples. Similarly, surface layers were removed by an AFM and analyzed by the photothermal deformation of the coated cantilever. This work shows that the AFM can function as both an infrared detector and a precise surface separation device for spectroscopic analysis. The AFM combined with an FT-IR has the potential to enhance the sensitivity, selectivity, and spatial resolution of infrared spectroscopy.

Measurement of Thermal Diffusivity Based on the Photothermal Displacement Technique Using New Phase Method.

A new analysis method of measuring the thermal diffusivity of a solid using photothermal displacement is proposed. To obtain an expression for the photothermal deformation, a homogeneous and isotropic infinite plate of finite thickness with stress-free boundaries is considered. Theoretical study was carried out to investigate the influence of the parameters, such as the radius and modulation frequency of the pump beam and the sample thickness. We obtained the thermal diffusivity from the phase of the signal by two methods. The first method for finding the thermal diffusivity of the theoretical result uses the bi-section method to minimize the standard deviation between experimental and theoretical phase curves. The second method uses the relation between the normalized thermal diffusion length and normalized minimum position. The experimental data obtained by applying these methods for different samples were in good agreement with the literature values.

Thermal diffusivity measurement of polymeric thin films using the photothermal displacement technique. I. Free-standing film case

The photothermal displacement technique has been used to measure the out-of-plane thermal diffusivity in free-standing polymer thin films. The technique can be applied to a single sample as well as a collection of samples of different film thickness. Polymers are well suited for this method because they usually possess a large vertical coefficient of thermal expansion and readily absorb UV laser radiation. In particular, this method yields a value of the thermal diffusivity for polymer films with thickness ranging from 125 to about 10 μm. Different polymers have been studied with particular attention paid to UPILEX-S (biphenyl tetracarboxylic dianhydride-p-phenyl diamine) polyimide whose thermal diffusivity has been determined to be 0.0025±0.0005 cm2/s. Our study shows that the measurements are not strongly affected by uncertainties in the optical absorption coefficient of the polymer as well as photothermal displacement contributions from the backside of the free-standing film. Furthermore, neither the effect of heat dissipation into the surrounding media of the polymer film nor miraging of the probe beam should significantly affect the results. Finally, analysis shows that the value of the thermal diffusivity determined is that of the out-of-plane value as long as the in-plane value is not orders of magnitude larger. This article is the first part of a two-part examination of the thermal properties of polymers using this nondestructive method.

Melting and Surface Deformation in Pulsed Laser Surface Micromodification of Ni-P Disks

Abstract The nanosecond pulsed laser-induced transient melting and miniature surface deformation of Ni-P hard disk substrates has been investigated experimentally. A photothermal displacement method has been developed to detect the transient melting and surface deformation process with nanosecond time resolution. The deflection signals show the variation of the feature shape in response to different pulse energies of the near-infrared pulsed nanosecond heating laser beam. A laser flash photography system is also developed to visualize the growth dynamics of the entire feature with nanosecond time resolution and submicron spatial resolution. The feature formation is explained as a result of surface tension driven flow. The surface tension depends not only on the surface temperature, but also on the surfactant concentration. Competition between the thermocapillarity and a surfactant concentration effect is revealed in the course of the bump formation process. Smaller features with diameters of 5 μm are obtained by using visible pulsed laser radiation. On-line monitoring of the transient growth process of such small features is achieved by a new laser flash deflection microscope. [S0022-1481(00)00301-7]

Photothermal displacement detection and transient imaging of bump growth dynamics in laser zone texturing of Ni–P disk substrates

A novel photothermal displacement method has been applied to probe the pulsed laser-induced feature formation of Ni–P hard disk substrates in the laser zone texturing process. The deflection signals of the reflected probing beam show the variation of the feature shape resulting from different pulse energies of the heating laser beam. A laser flash photography system is also developed to visualize the feature growth dynamics. This system has nanosecond time resolution and about one micron spatial resolution. Both techniques show clearly the transient melting and deformation process and the time scale of such deformation.

Temperature dependence of the thermal diffusivity of GaAs in the 100–305 K range measured by the pulsed photothermal displacement technique

We have measured the variation of the value of the thermal diffusivity of semi-insulating GaAs in the 100–305 K range. The method used is the pulsed photothermal displacement technique. This is a noncontact technique, and the value of the thermal diffusivity is derived from the temporal evolution of the signal rather than its amplitude. This makes the technique less susceptible to uncertainties. We find that the temperature dependence of the thermal conductivity of semi-insulating GaAs follows a power law as T−1.62, in disagreement with results obtained previously. Possible reasons for the deviation within this very important intermediate temperature range are discussed.

Laser-Induced Photothermal Displacement Spectroscopy (LIPDS) for Speciation of Lanthanides and Actinides

Laser-Induced Photothermal Displacement Spectroscopy (LIPDS) for Speciation of Lanthanides and Actinides

Photothermal displacement measurement of transient melting and surface deformation during pulsed laser heating

A photothermal displacement method has been developed to probe the pulsed laser-induced transient melting and surface deformation of Ni–P hard disk substrates. A probing He–Ne laser beam is aligned collinearly with the near-infrared nanosecond pulsed heating beam. The He–Ne beam spot is scanned on the microfeatures formed on the sample surface by the pulsed laser heating. The deflection signals show the variation of the feature shape resulting from different pulse energies of the heating laser beam. The transient deflection signal also reveals that the time scale of the surface motion is in the range of several hundred nanoseconds.

Thermal diffusivity measurement of solid materials by the pulsed photothermal displacement technique

A simple, noncontact technique for the measurement of thermal diffusivity of solids is experimentally demonstrated. The technique is based on the photothermal displacement effect. Excellent agreement between the quasistatic theory of photothermal displacement and the experiment has been obtained. The technique has been demonstrated by measuring the thermal diffusivities of GaAs and InGaAs/AlGaAs multiple quantum wells.

Defect induced laser damage in oxide multilayer coatings for 248 nm

Photothermal displacement microscopy is used for the detection of μm-sized defects in Al 2O 3/SiO 2 multilayer coatings highly reflective for 248 nm. It is shown that for high quality coatings the global (averaged over several cm 2) laser-induced damage threshold for coatings of different quality is determined by the density and absorption strength of the light absorbing defects. This is confirmed by a measurement of local (averaged over 0.01 mm 2) damage thresholds with the pulsed photoacoustic mkage technique allowing a dkect correlation of local damage with photothermally detected thin film defects. An analysis of laser-damaged spots reveals damage-craters of 13 μm diameter at the onset of detrimental irradiation effects. The formation of these craters is explained by a thermoelastic model describing the tensile stress in the film system resulting from evaporation of a defect located at the interface between thin film and substrate.

Measurement of the Thermal Conductivity of Si and GaAs Wafers Using the Photothermal Displacement Technique

Thermal conductivity and thermal diffusivity of Si and GaAs wafers were measured using the photothermal displacement technique, and the temperature dependence of these two quantities was investigated. Thermal diffusivity was obtained from the phase difference between the heating source and the signal, and thermal conductivity was determined from the maximum value of the signal amplitude in the temperature range 80 to 300 K. It was verified that an increase in doping concentration gives rise to a decrease in thermal conductivity at low temperatures. The experimental results obtained on samples with different types and doping concentrations are consistent with those expected from theoretical considerations.

Applications of photothermal displacement spectroscopy to the study of asphaltenes adsorption

We have developed an application of photothermal surface deformation (PTD) to study asphaltenes adsorption on inorganic surfaces. Using an appropriate ratio of the probe and excitation beam spot size at the sample surface we have been able to measure the magnitude of the PTD using a single photodiode detector. The magnitude of the PTD signal is shown to be related to the amount of adsorbed asphaltene. This technique offers a direct non-perturbing and completely contactless detection of adsorbed asphaltenes. Solute-solid adsorption isotherms (SSA) of asphaltenes from two Venezuelan extra-heavy oil (Jobo and Hamaca) were measured using a glass thin plate as adsorbent. The results obtained are in good agreement with those reported using conventional indirect techniques but better precision is achieved.

Bistability of a self-standing film caused by photothermal displacement

We report on the bistability of a self-standing thin film caused by photothermal displacement. The sample consisted of a self-standing thin film placed in front of a mirror. By irradiating the self-standing thin film with continuous wave laser light, the self-standing thin film deflected with thermoelastic bending moment. Since a standing wave of the laser light was generated by the reflection of the mirror, the bending moment generated on the film was periodic along the optical axis. The displacement of the film was found to be bistable with the laser light intensity. Simultaneously, the light intensity reflected from the sample was also bistable. These phenomena are explained by the photothermal displacement of thin film in the standing wave of laser light.

A Novel Laser-Induced Photothermal Displacement Spectroscopy (LIPDS) for Detection and Speciation of a Metal Ion in Aqueous Solution

A Novel Laser-Induced Photothermal Displacement Spectroscopy (LIPDS) for Detection and Speciation of a Metal Ion in Aqueous Solution

A Novel Laser-Induced Photothermal Displacement Spectroscopy (LIPDS) for Detection and Speciation of a Metal Ion in Aqueous Solution.

Click to increase image sizeClick to decrease image sizeKEYWORDS: laser-induced photothermal displacement spectroscopyoptical heterodyne interferometersdetectionspeciationchemical state metal ionsaqueous solutionsactinideslanthanidessensitivityremote handling