Photothermal Deflection Method Research Articles

Measuring Thermal Diffusivity of Azoheteroarene Thin Layers by Photothermal Beam Deflection and Photothermal Lens Methods.

Measurement of thermal properties of thin films is challenging. In particular, thermal characterization is very difficult in semi-transparent samples. Here, we use two photothermal methods to obtain information about the thermal diffusivity as well as thermal conductivity of azoheteroarene functionalized polymer thin layers. The photothermal beam deflection (PBD) method is employed to gather data directly on thermal conductivity and thermal diffusivity, while the thermal lens (TL) method is employed to measure the effective thermal diffusivity. Consequently, the thermal diffusivity of the layers is indirectly estimated from the effective thermal diffusivity using a well-established theoretical relationship. Despite the utilization of distinct methods, our study reveals a remarkable consistency in the highly accurate results obtained from both approaches. This remarkable agreement reaffirms the reliability and mutual compatibility of the employed methods, highlighting their shared ability to provide accurate and congruent outcomes.

Thermal diffusivity of molybdenum oxide nanowire film: A photothermal beam deflection study

The paper reports the preparation of thin film with MoO3 nanowires (NWs) by the doctor blade method and the study of its thermal diffusivity (α) by the sensitive photothermal beam deflection (PTD) method. When the Field Emission Scanning Electron Microscopic and Atomic Force Microscopic analysis unveil its morphology as NW bundles, the X-ray diffraction analysis reveals the structure to be orthorhombic. The NWs formed are of diameter ~ 20 nm and length up to 5 μm. The standardization of the transverse PTD setup is done by determining the value of α of iron, which agrees well with literature reports. The thermal diffusivity of MoO3 NW film is obtained as 0.0036 cm2/s, which is 9.48% of its bulk counterpart. The reduction in the thermal diffusivity of NW makes it a suitable candidate for thermoelectric applications.

Research on Measuring Thermal Conductivity of Quartz and Sapphire Glass Using Rear-Side Photothermal Deflection Method

As the display industry continues to advance, various new materials are being developed for utilizing microtechnology and nanotechnology in display panels. Among these, transparent materials have been widely applied to the internal wiring of displays and flexible substrates, owing to their high optical transmittance, isotropy, and anisotropy. Thus, measurement of the thermophysical properties of various transparent materials is important. This study measured thermal conductivity by selecting quartz, a transparent isotropic material, and sapphire glass, a transparent anisotropic material, as measurement target materials using a rear-side photothermal deflection method. Measurements were made via a three-dimensional unsteady heat conduction equation, to which complex transformation was applied and numerically analyzed using COMSOL Multiphysics. Phase delays for a pump beam and a probe beam for a relative position were derived through a deflection analysis. From the derived phase delays between the numerical analysis and experimental result with optical alignment, the absolute and relative errors of quartz were appropriately confirmed to be 0.069 W/m-K and 5%, respectively, while those of the sapphire glass were likewise confirmed to be 0.55 W/m-K and 1.5%, respectively.

Thermal Relaxation Spectra for Evaluating Luminescence Quantum Efficiency of CASN:Eu2+ Measured by Balanced-Detection Sagnac-Interferometer Photothermal Deflection Spectroscopy

Highly sensitive broadband photothermal spectroscopy with a white-light lamp as the excitation source was developed by combining a Sagnac interferometer and balanced detection with a photothermal deflection method. A probe beam was split by a birefringent crystal CaCO3 into signal and reference beams with a balanced intensity. This balanced detection enabled the measurement of photoexcited thermal relaxation spectra of materials in the air over the whole visible range in the weak excitation limit 50 µW/cm2. The photothermal excitation spectrum of Eu2+-doped CaAlSiN3 phosphors (CASN:Eu2+) with a high luminescent quantum efficiency was measured to be distinctly different from the photoluminescence excitation spectrum which reflects the absorption spectrum, revealing the thermal relaxation mechanism of the phosphor. Assuming a typical non-radiative relaxation from the higher excited states to the lowest excited state and successively to the ground state, it is demonstrated that the photoluminescence efficiency of the phosphors is readily evaluated simply by comparing the photothermal and photoluminescence excitation spectra.

Heat transfer through soldered and bonded joints of multilayer semiconductor devices studied by laser photothermal beam-deflection method

Thermal wave propagation through solid-solid non-ideal interfaces in multilayer semiconductor devices is considered. A theoretical model is developed for thermal wave propagation, and the laser photothermal probe beam deflection method is used for experimental study of heat transport through multilayered samples with vertical joint interfaces. Experimental and theoretical results are presented for bonded and soldered joints. It is shown that, in general case, both the thermal resistance and the heat capacity of the joint should be considered to describe adequately experimental data and to determine thermophysical properties of a separate layer. It is shown that the real thermal resistance of a soldered joint may be much higher than the predicted one basing on tabulated characteristics. The paper demonstrates that the laser photothermal beam-deflection methods can be applied for testing the thermal contact quality between elements of multilayered semiconductor structures, for example, a multijunction solar cell, assembling by various technologies. These methods make possible to evaluate quantitatively the thermal resistance and heat capacity of thermal contacts at the micrometer scale.

Deep Thermal Investigations on Ag2S Thin Film Along With Electropyroelectric and Photothermal Deflection Techniques

Nowadays, experiments based on possible obtaining of the thermal proprieties of sulphide semiconductor materials as thin films are in progress. Moreover, to reach by calculation, the thermal constants, such as the thermal conductivity, as well as the thermal diffusivity, of such films remains a principal challenge for many of research teams working in optoelectronic and sensitivity devices. This work covers a new theoretical model of the front-detection electropyroelectric configuration, leading to the determination of the thermal parameters of thin films. A normalisation procedure relative to an empty pyroelectric sensor is used to eliminate instrumental factor. Herein, obtained thermal conductivity and the thermal diffusivity of silver sulphide Ag2S are of the order of 0.90 W. $\text{m}^{-}1\cdot\text{K}^{-1}$ and $4.52\,\,10^{-7}\text{m}^{2}\cdot\text{s}^{-1}$ , respectively. These values match correctly with the thermal measurements based on well-known photothermal deflection method, which validates our theoretical model.

Analytical Study of the Thermal and Optical Properties Effect on the Collinear Deflection Method

Recently, study of transparent materials, such as thin film form, have an important field for the development of advanced electronic devices. Therefore, the need for the precision thermal property measurement techniques of transparent thin film materials becomes increasing according to the development of these material. The ideal methods for optically measurements of these properties are noncontact method. However, optically measurements are often difficult due to the transparency. So, transparent materials have not enough temperature gradient in the air layer above thin films. To solve this problem, we used the collinear deflection method which is one of the photothermal deflection methods. In the measurement process, both of the pump beam and probe beam are irradiated vertically on the transparent sample. And the probe beam is deflected by refractive index variation of samples due to the temperature gradient inside samples.The purpose of this study is to analyze the effect of thermal and optical properties analytically on the collinear deflection method for variable materials.

Anti-integrin and integrin detection using the heat dissipation of surface plasmon resonance

We verified that the heat dissipation of surface plasmon resonance can be measured using photothermal deflection method. The maximum value of photothermal deflection corresponded to the occurrence of surface plasmon resonance. The detection of anti-integrin and integrin biomolecules that exhibit specific binding was demonstrated using this technique. From our experimental results it shows that the photothermal deflection method can be used to obtain the surface plasmon resonance angles and angle shift.

Thermal diffusivity measurements on ternary Ge–Te–Tl glasses using Photo-thermal Deflection method: Effect of thallium addition

Photo-thermal Deflection (PTD) technique is used to investigate the thermal diffusivity (α) of Ge17Te83−xTlx (0≤x≤13) glasses as a function of composition. The thermal diffusivity of these glasses is found to lie in the range 0.020 to 0.048cm2/s, which is consistent with the memory type of electrical switching exhibited by these samples. Further, it is found that α shows an initial increase with Tl addition, followed by a decrease. The observed composition dependence of thermal diffusivity has been understood on the basis that the thallium atoms are incorporated as a covalent species for lower values of x, increasing the network rigidity; however, they enter as ionic species for higher x values, fragmenting the network. The initial increase in α is due to the increasing network rigidity and the subsequent decrease is because of the fragmentation of the network. Also, there is a strong correlation between the composition dependence of switching voltages observed earlier and the variation with composition of electrical resistivity and thermal diffusivity of Ge17Te83−xTlx glasses obtained in the present study.

Investigation of thermal and optical properties of thin WO3 films by the photothermal Deflection Technique

Owing to its novel physical properties, as well as its technological implication in many fields, the thermal and optical properties of WO3 thin films are studied here. These thin films are prepared from Ammonium Tungstate and deposited on a glass substrate at 400°C by the Spray Pyrolysis Technique. The thermal properties (Thermal conductivity and thermal diffusivity) were studied by the Photothermal Deflection method in its uniform heating case instead of traditionally a non uniform heating one by comparing the experimental amplitude and phase variations versus square root modulation frequency to the corresponding theoretical ones. The best coincidence between theory and experience is obtained for well-defined values of thermal conductivity and thermal diffusivity. The optical properties (optical absorption spectrum and gap energy) were measured using the Photothermal Deflection Spectroscopy (PDS) by drawing the amplitude and phase variation versus wavelength in experimental way and versus absorption coefficient in theoretical one at a fixed modulation frequency. By comparing point by point the normalised experimental and corresponding theoretical amplitude variation, one can deduce the optical absorption spectrum. Using the Tauc law for energies above the gap we can deduce the gap energy. We notice that these films show low thermal conductivity and high transparency in the visible range.

Investigation of thermal properties of Sulfosalt SnSb2S4 thin films by the Photothermal Deflection Technique

The thermo-physical properties of sulfosalt SnSb2S4 thin films deposited at two different glass substrate temperatures by Thermal Evaporation were investigated using the Photothermal Deflection method in its uniform heating case instead of traditionally a non uniform heating one. The advantage of applying this method in this way lies in its simplicity and its sensitivity to both thermal conductivity and thermal diffusivity. These films undergo abrupt changes in thermal properties on both sides of the transition temperature of 140°C which may be show the influence of the substrate temperature on thermal properties of the material.

Determination of thermal diffusivity of ceramics by means of photothermal beam deflection

The non-contact and non-destructive photothermal beam deflection (PBD) method has been used for the characterization of the thermal properties of Alumina (Al2O3), Mullite (3Al2O3·2SiO2) and Oxidic-Bonded Silicon Carbide (OBSiC) samples often used in chemical engineering. Measurements of thermal diffusivity κ have been performed. One obtains for Alumina, for Mullite and for OBSiC.

Comparison between different Photothermal Deflection methods to determine thermal properties of bulk semiconductor samples

In this study we will describe and compare different methods based on the Photothermal Deflection Technique (PTD) which permits the determination of thermal diffusivity for bulk semiconductors. The two first methods proposed here consist in drawing the experimental amplitude and phase variation of the photothermal signal versus square root modulation frequency. The sample placed in air is heated thanks to a modulated uniform light beam. The difference between these two methods is that in the second one the sample is covered by a thin graphite layer. We notice that the first method is only sensitive to the thermal diffusivity however the second method is sensitive for both thermal diffusivity and thermal conductivity. Finally the third method which is a spectroscopic one and where the sample is immersed in a CCl4 filled cell consists to draw the phase variation of the photothermal signal versus wavelength at a fixed modulation frequency. The phase difference between the two saturated zone (high and low absorption coefficient) is sensitive to the thermal diffusivity.

Time Resolved Thermodynamic Studies of Ligand Binding/release to Sol-Gel Encapsulated Horse Heart Myoglobin

The successful confinement of proteins in solid state materials allows for a multitude of applications in the study of protein dynamics, as well as, advances in biotechnologies. The importance of bulk solvent and restricted space on the conformational dynamics of proteins can be identified by encapsulating the biomolecules (peptides, proteins, enzymezes, etc) in environments where both can be regulated. In addition, the affect of encapsulation on ligand binding and preservation of reactivity once encapsulated are of equal importance. With the use of Photoacoustic calorimetry (PAC) and Photothermal beam deflection (PBD) methods along with picosecond-millisecond transient absorption and fluorescence techniques we are investigating enthalpy, molar volume changes, and kinetics associated with with CO dissociation and rebinding to horse heart myoglobin encapsulated in sol-gels. Preliminary PAC data suggest that the dissociation of CO from HHMb results in four kinetic phases: <7ns, ∼125ns, ∼260ns, and ∼600ns. We will discuss the differences in molar volume and enthalpy changes associated with the conformational dynamics of these events in sol-gels relative to native protein in aqueous solution.

The measurement of thermal conductivities using the photothermal deflection method for thin films with varying thickness

This study considers non-contact methods that obviate the causes of measurement error, such as thermal contact resistance and the unnecessary destruction of samples. Among the methods, the photothermal deflection method has been adopted and developed to measure the thermal conductivities of thin-film materials. To apply the developed method for thin films, bi-layered materials are manufactured by depositing the film on Corning 7740 glass plates. The study also investigates the optimal modulation frequency, as related to the thermal diffusion length of the sample, for measuring thermal conductivities of thin films.. Aluminum, TiO2, and Si3N4 films with micro/nanometer thickness were selected as the objects for measurement; the thermal conductivities of these films were experimentally measured. Samples of thickness ranging from 1 µm to 200 nm were prepared to measure the variations in thermal conductivities with thickness. It was observed that the thermal conductivity in submicroscale films decreased as the thickness was reduced.

A composite photothermal technique for the measurement of thermal properties of solids

In this work, a composite photothermal technique combining open photoacoustic cell and photothermal deflection methods for thermal characterization of opaque solids was developed. An excitation laser was employed to concurrently generate both photoacoustic and mirage effects. Thermal diffusivity and thermal effusivity of carbon-based samples were measured, and the values of thermal conductivities and specific heat were then deduced. The experimental results were found to be in good agreement with the literature values. The photothermal technique developed in this work permits a convenient and precise measurement of thermal properties of solids.

Thermal conductivity measurement of anisotropic material using photothermal deflection method

A complete theoretical treatment of photothermal deflection spectroscopy has been performed for the measurement of thermal conductivities in an anisotropic medium. An analytical solution of three-dimensional heat conduction was obtained by using 2D Fourier Transforms for an anisotropic material irradiated by a laser beam. Thermal conductivity was determined by using the phase angle of deflection at relative positions between the heating and probe beams. Excellent agreement between theoretical and experimental photothermal deflections was obtained. Also, the thermal conductivity in an arbitrary measurement direction for anisotropic materials (Pyrolytic graphite) was measured.

Measurement of Thermal Conductivity for Single- and Bilayer Materials by Using the Photothermal Deflection Method

Measurement of Thermal Conductivity for Single- and Bilayer Materials by Using the Photothermal Deflection Method

Volume and enthalpy profiles of CO rebinding to horse heart myoglobin.

Carbon monoxide binding to myoglobin was characterized using the photothermal beam deflection method. The volume and enthalpy changes coupled to CO dissociation were found to be 9.3+/-0.8 mL x mol(-1) and 7.4+/-2.8 kcal x mol(-1), respectively. The corresponding values observed for CO rebinding have the same magnitude but opposite sign: Delta V=-8.6+/-0.9 mL x mol(-1) and Delta H=-5.8+/-2.9 kcal x mol(-1). Ligand rebinding occurs as a single conformational step with a rate constant of 5 x 10(5) M(-1) s(-1) and with activation enthalpy of 7.1+/-0.8 kcal x mol(-1) and activation entropy of -22.4+/-2.8 cal x mol(-1) K(-1). Activation parameters for the ligand binding correspond to the activation parameters previously obtained using the transient absorption methods. Hence, at room temperature the CO binding to Mb can be described as a two-state model and the observed volume contraction occurs during CO-Fe bond formation. Comparing these results with CO dissociation reactions, for which two discrete intermediates were characterized, indicates differences in mechanism by which the protein modulates ligand association and dissociation.

Photothermal studies of pH induced unfolding of apomyoglobin.

Conformational dynamic and enthalpy changes associated with pH induced unfolding of apomyoglobin were studied using photoacoustic calorimetry and photothermal beam deflection methods. The transition between the native state and the I intermediate was induced by a nanosecond pH jump from o-nitrobenzaldehyde photolysis. Deconvolution of photoacoustic waves indicates two kinetic processes. The fast phase (T < 50 ns) is characterized by a volume expansion of 8.8 ml mol(-1). This process is followed by a volume contraction of about -22 ml mol(-1) (tau approximately 500 ns). Photothermal beam deflection measurements do not reveal any volume changes on the time scale between approximately 100 micros and 5 ms. We associate the volume contraction with structural changes occurring during the transition between the native state and the I intermediate. The lack of any processes on the ms time scale may indicate the absence of structural events involving larger conformational changes of apomyoglobin after the pH jump.