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•Molybdenum (Mo) thin films were grown on AlN by pulsed laser deposition for heat sink applications.•Smooth and crystalline Mo films were obtained at 600 ˚C and 10 mTorr of Argon ...gas.•Thermal diffusivity was measured by photo-thermal surface displacement using an IR laser.•Under optimal deposition conditions, a thermal diffusivity very close to that of bulk Mo was obtained.•The Mo-AlN system was found to be stable up to an operating temperature of 200 °C.
Thin films of molybdenum (Mo) were grown on aluminium nitride (AlN) substrates by pulsed laser deposition for heat sink applications. The effect of experimental growth parameters on the films’ structural properties were investigated by Scanning Electron Microscopy, X-Ray Diffraction and Atomic Force Microscopy. Thermal characterization was achieved by measuring the in-plane thermal diffusivity of the grown layers by means of a photothermal beam deflection technique using an IR heating laser. Within the experimental parameters studied in this work, a substrate temperature of 600 ˚C and an ambient argon gas pressure of 10 mTorr were identified as the optimal growth conditions for the synthesis of smooth and well-crystallized Mo layers. Concurrently, the thermal diffusivity of the films is significantly affected by film growth parameters. Under the optimal growth conditions, a thermal diffusivity value as high as 5.42x10-5 m2/s was measured, a value that is very close to that of bulk Mo, and which would be a result of the synthesis of polycrystalline Mo films whose grains’ size is greater than the heat carriers mean free path, namely the free electrons. The temperature dependence of the thermal diffusivity was also investigated, and the films were found to be stable up to an operating temperature of 200 °C. Beyond this temperature, photothermal beam deflection imaging shows the onset of film delamination from the underlying substrate.
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•Combination of interdisciplinary analytical tools for analysis of multi-layered coatings.•First use of photothermal beam deflection spectroscopy for coating evaluation.•New testing ...platform for medical grade steel materials for biomedical applications.
In this comprehensive study several analytical techniques were used in order to evaluate multi-layered biomedical surface coatings composed of a drug (diclofenac) and a polymer (chitosan). Such a thorough examination is of paramount importance in order to assure safety and prove efficiency of potential biomedical materials already at the in vitro level, hence leading to their potentially faster introduction to clinical trials.
For the first time a novel technique based on thermal diffusivity and conductivity measurements (photothermal beam deflection spectroscopy – BDS) was employed in order to analyse in a non-destructive way the thickness of respective layers, together with their thermal diffusivity and conductivity. In addition to attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), BDS confirmed successive surface layers of the prepared coatings. Scanning electron microscopy and atomic force microscopy were used to examine structural information on the macro- and micro/nano-scale, respectively. Surface hydrophobicity was measured with the contact angle analysis, which clearly showed differences in hydrophobicity between coated and non-coated samples. Considering the targeted application of the prepared coatings (as implant in orthopaedic treatments), the in vitro drug release was analysed spectrophotometrically to examine the coatings potential for a controlled drug release. Furthermore, the material was also tested by electrochemical impedance spectroscopy and cyclic polarisation techniques, which were able to detect even minor differences between the performance of the coated and non-coated materials. As the final test, the biocompatibility of the coatings with human osteoblasts was determined.
•Quantum confined effects in nanowires (NWs) make it technologically significant.•Investigates the thermal diffusivity of MoO3 NW films by mirage technique.•MoO3 NW film exhibit a thermal ...diffusivity, 9.48% of the bulk counterpart.•Study reveals the potential of MoO3 NW for thermoelectrics and optronics applications.
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.
•Microscopic of CdSe/ZnS using anti-Stokes luminescence was confirmed.•Newly proposed photothermal deflection technique does not require multiple lasers.•Deflection of probe beam with respect to pump ...beam is an indicator of cooling.
Photothermal deflection spectroscopy (PDS) is a highly sensitive and precise technique that is used to measure the optical absorption and thermal characteristics of a sample. While most applications of PDS utilize a heating beam, laser cooling of solids, or optical refrigeration as it is sometimes called, use this technique to determine if a laser is cooling or heating a sample. Current PDS methods for laser cooling require multiple laser wavelengths in both the Stokes and anti-Stokes region to ensure that cooling is occurring. This can cause problems if lasers must be changed or no lasers in the desired wavelength are available. Herein, we present a photothermal deflection technique that uses the deflection of the probe laser to determine if microcooling is occurring inside a sample.
The influence of P3HT:PCBM ratio on thermal and transport properties of solar cells were determined by photothermal beam deflection spectrometry, which is advantageous tool for non-destructively ...study of bulk heterojunction layers of organic solar cells. P3HT:PCBM layers of different P3HT:PCBM ratios were deposited on top of PEDOT:PSS/ITO layers which were included in organic bulk-heterojunction solar cells. The thermal diffusivity, energy gap and charge carrier lifetime were measured at different illumination conditions and with a different P3HT:PCBM ratios. As expected, it was found that the energy band gap depends on the P3HT:PCBM ratio. Thermal diffusivity is decreasing, while charge carrier lifetime is increasing with PCBM concentration. Energy band gap was found to be independent on illumination intensity, while thermal diffusivity was increasing and carrier lifetime was decreasing with illumination intensity. The carrier lifetime exhibits qualitatively similar dependence on the PCBM concentration when compared to the open-circuit voltage of operating solar cells under AM1.5 illumination. BDS and standard I-V measurement yielded comparable results arguing that the former is suitable for characterization of organic solar cells.
This article presents the results of comparative investigations of thermal parameters of hybrid sol–gel coatings (named TMZ) prepared from tetraethyl orthosilicate and organically modified ...3-methacryloxypropyltrimethoxysilane. The coatings were prepared with the addition of zirconium(IV) tetrapropoxide chelated with methacrylic acid. Two series of samples were investigated: the first series, TMZ-I, TMZ-II and TMZ-III, with different amounts of zirconium, and the second series, TMZ-I/Ce, TMZ-II/Ce and TMZ-III/Ce, with the addition of cerium nitrate. The influence of the amount of zirconium and cerium on the thermal parameters of the sol–gel coatings was next analyzed. Two non-destructive and photothermal techniques were used for this purpose: photothermal radiometry (PTR) and beam deflection spectroscopy (BDS). The thermal diffusivity and conductivity of the coatings were extracted from the frequency experiments and are presented and discussed. The two-layer model was applied to interpret the photothermal spectra. The results obtained using these two techniques are compared and discussed.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).Photothermal techniques rely on light induced heating mechanisms to evaluate various optical, thermal and electronic ...properties of materials. In this work, photothermal beam deflection technique is employed to investigate non-radiative transitions occurring within the conduction band and defect bands of beta -In sub(2)S sub(3) thin films. Heat generation from beta -In sub(2)S sub(3) thin films is triggered using laser beams of wavelength 488, 532 and 632 nm. A probe laser beam of wavelength 546 nm is used to measure the heat generation and distribution in the samples. Thermal diffusivity (D sub( )th, electronic carrier mobility ( mu ), lifetime ... and surface recombination velocity (V sub( )sr are measured by fitting the theoretical and experimental photothermal response. The photothermal response and transport properties of the beta -In sub(2)S sub(3) thin films with varying percentage of chlorine as dopant is studied to understand the role of chlorine. The presence of chlorine in these films have increased the electronic mobilty and carrier lifetime by an order of 10 by passivation of surface defects.
Photothermal beam deflection spectroscopy (BDS) with a red He–Ne laser (632.8 nm, 35 mW) as an excitation beam source and a green He–Ne laser (543.1 nm, 2 mW) as a probe was used for estimating ...thermal diffusivity of several types of soil samples and individual soil aggregates with small surfaces (2 × 2 mm). It is shown that BDS can be used on demand for studies of changes in properties of soil entities of different hierarchical levels under the action of agrogenesis. It is presented that BDS clearly distinguishes between thermal diffusivities of different soil types: Sod-podzolic Umbric Albeluvisols, Abruptic, 29 ± 3; Chernozem typical Voronic Chernozems, Pachic, 9.9 ± 0.9; and Light Chestnut Haplic Kastanozems, Chromic, 9.7 ± 0.9 cm
2
·h
−1
. Aggregates of chernozem soil show a significantly higher thermal diffusivity compared to the bulk soil. Thermal diffusivities of aggregates of Chernozem for virgin and bare fallow samples differ, 53 ± 4 cm
2
·h
−1
and 45 ± 4 cm
2
·h
−1
, respectively. Micromonoliths of different Sod-podzolic soil horizons within the same profile (topsoil, depth 10–14 cm, and a parent rock with Fe illuviation, depth 180–185 cm) also show a significant difference, thermal diffusivities are 9.5 ± 0.8 cm
2
·h
−1
and 27 ± 2 cm
2
·h
−1
, respectively. For soil micromonoliths, BDS is capable to distinguish the difference in thermal diffusivity resulting from the changes in the structure of aggregates.
•Method for determining thermo-optical and transport parameters during one measurements is proposed.•Characterization of ε-Fe2O3-based nanomaterials supported on Si(100) is performed.•Strategy for ...enhancing the lifetime of photogenerated charge carriers and decreasing the Eg values is described.•A way of enhancement of the material’s thermal properties is presented.•Development of more efficient nanocomposite systems for light-activated applications is achieved.
In this work, photothermal beam deflection (PBD) experiments have been used to characterize the thermooptical and transport properties of ε-Fe2O3-based nanocomposites. In particular, iron(III) nanostructures have been functionalized with Au, Ag and Cu nanoparticles, tailoring both their nano-organization and their chemical state. In order to elucidate the correlation between the thermooptical and transport parameters, the structural, compositional and morphological properties of Fe2O3-based systems were studied by field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). It was observed that the optothermal and transport parameters were influenced by the nature and oxidation state of the nanoparticles, which can serve as a key tool to master the material properties for their application in light-assisted processes.
The preponderance of laser beam shapes cannot be ruled out during the implementation of an optical experiment nor during the formulation of its theoretical background. The present work elucidates the ...role of Gaussian and top-hat beam shapes in generating and analysing the photothermal beam deflection (PBD) signals. The complex geometrical optics models encompassing the perturbations in the phase and amplitude of the probe beam with one-dimensional (1D) and two-dimensional (2D) approaches is employed to curve fit the PBD signal and are compared. From the fitted curve, the thermal diffusivity and conductivity of the sample are calculated with the 1D and 2D models. A uniform intensity distribution over the sample, like a top-hat beam, is achieved using an optical lens system and verified using a beam profiler. When the phase and amplitude of the PBD signal are fitted at different positions of the lens, i.e., in focussed and defocussed conditions, it is observed that difference in the measured thermal characteristics is about 30% for the Gaussian pump beam profile, whereas it is only <4% for top-hat beam. Even though the fitting accuracy and sum of residues estimated for the 2D model are better than 1D, the ease of computation with the 1D model employing top-hat excitation suggests the application of the top-hat profile in photothermal experiments.
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