Search

Photothermal imaging is useful for detecting individual nanoparticles and obtaining the absorption spectra. This study presents a wide-field photothermal reflectance spectroscopy technique achieved by incorporating a pump beam, a probe beam, and a charge-coupled device (CCD) camera into a commercial microscopic setup. The presented design does not require precise alignment between the pump and the probe beams and enables the observation of numerous individual nanoparticles during image acquisition. Despite the use of a simple imaging processing method, i.e., a four-bucket method using a CCD camera, sufficient sensitivity for the spectral imaging of a single gold nanorod (20 nm diameter and 84 nm length) is demonstrated. Numerous individual nanoparticles within a wide field of view (240 μm × 180 μm) are detected in an image captures at an imaging measurement speed of 0.02 mm2 min−1. Furthermore, the proposed photothermal reflectance spectroscopy technique can detect the variation in the absorption peak of the measured spectra depending on the aspect ratio of individual nanoparticles within a spectral resolution of 1 nm.

This study presents a straightforward, efficient dual-mode thermoreflectance microscopy (TRM) system for analyzing the stationary and dynamic thermal properties of microelectronic devices. The proposed TRM system employs a standard visible microscope and implements two distinct imaging process schemes to obtain thermal images at different time scales. For TRM imaging of an ohmic microdevice, the optimal probing wavelength is predetermined from the thermoreflectance spectrum, acquired using a white light-emitting diode source and tunable bandpass filters to enhance thermal sensitivity. Thermoreflectance images are obtained in both stationary and transient modes using a four-bucket method and a pulsed boxcar averaging method, respectively. This thermography approach demonstrates highly sensitive, time-integrated stationary thermal imaging and time-gated transient thermal imaging with a temporal resolution of 200 ns. The system shows significant potential as an analytical tool with a sub-micron spatiotemporal resolution for evaluating heat generation and self-heating behavior in microelectronic devices. [ABSTRACT FROM AUTHOR]

Hollow, microrod-like Pt nanostructures are locally synthesized on a small, suspended microheater platform (9 μm × 110 μm) as the catalytic layer of a low-power hydrogen (H2) catalytic combustion sensor. The Pt nanostructures are synthesized via two successive Joule heating-assisted chemical reactions. During operation, H2 locally combusts on the surface of the Pt nanostructures and transfers heat to the microheater, which in turn changes its resistance. Because of the highly localized Pt nanostructures and the suspended microheater, the sensor exhibits high sensitivity (ΔR/R0 ∼ 0.46% per percent of H2), fast response and recovery speeds (<12 s), and low-power consumption (4 mW). [ABSTRACT FROM AUTHOR]

In this paper, we propose a sensitivity-enhanced thermoreflectance microscopy (TRM) system employing an electronic auto-balancing photoreceiver for effective thermal fault localization through a Si substrate. The proposed system in the auto-balanced detection not only improves the system signal-to-noise ratio (SNR) by approximately five times compared to that achievable via normal detection but also mitigates the inherent system noise, such as pseudothermoreflectance signals, by using the optical zooming. Moreover, temperature variations as small as ~47 mK were detectable under the measurement conditions employed in this paper. Finally, we experimentally demonstrated clear localization of a thermal fault, which was dimly visible in the normal backside detection results, in an optical zoomed thermal image. [ABSTRACT FROM AUTHOR]

In this study, a thermal method for erasing and permanently destroying data stored in flash memory fabricated on a suspended silicon nanowire is demonstrated. An intentionally applied heat treatment is used to erase the data stored in the charge trap layer of the flash memory. The data destruction is verified and analyzed at a unit cell level as well as in a commercial off-theshelf chip. Characteristics of memory performance and reliability are also investigated. Then, the feasibility of the proposed method is further evaluated for next generation 3-dimensional V-NAND. [ABSTRACT FROM AUTHOR]

We report parallel spectral-domain optical coherence tomography (OCT) at 500 000 A-scan/s. This is the highest-speed spectral-domain (SD) OCT system using a single line camera. Spectrally encoded line-field scanning is proposed to increase the imaging speed in SD-OCT effectively, and the tradeoff between speed, depth range, and sensitivity is demonstrated. We show that three imaging modes of 125k, 250k, and 500k A-scan/s can be simply switched according to the sample to be imaged considering the depth range and sensitivity. To demonstrate the biological imaging performance of the high-speed imaging modes of the spectrally encoded line-field OCT system, human skin and a whole leaf were imaged at the speed of 250k and 500k A-scan/s, respectively. In addition, there is no sensitivity dependence in the B-scan direction, which is implicit in line-field parallel OCT using line focusing of a Gaussian beam with a cylindrical lens. [ABSTRACT FROM AUTHOR]

Proposed herein is a new technique of activation for the backplane of low-temperature amorphous indium gallium zinc oxide thin-film transistors (a-IGZO TFTs) by applying a bias voltage to gate, source, and drain electrodes and simultaneously annealing them at 150°C. This ‘voltage bias activation’ can be an effective method of reducing the backplane processing temperature from 300°C to 150°C. Compared with the reference a-IGZO TFTs fabricated at 300°C, the a-IGZO TFTs fabricated through voltage bias activation showed sufficient switching characteristics: 10.39 cm2/Vs field effect mobility, 0.41 V/decade subthreshold swing, and 3.65 × 107on/off ratio. These results were analyzed thermodynamically using infrared micro-thermography. In the case of the positive gate voltage bias condition, the maximum temperature of the a-IGZO channel increased to 48°C, and this additional annealing effect and activation energy lowering compensated for the insufficient thermal energy of annealing at a low temperature (150°C). With this approach, a-IGZO TFTs were successfully fabricated at a low temperature. [ABSTRACT FROM AUTHOR]

In this work, a facile synthetic process is reported for the large-scale synthesis of Fe3O4 nanocrystals. Thermal decomposition of Fe(acac)3 (100 g) in 1-hexadecanol produced Fe3O4 nanocrystals with well-controlled sizes and morphologies. The nanocrystals were spherically shaped with average diameters of 7.8 ± 0.6, 6.5 ± 0.4, and 5.9 ± 0.2 nm when prepared at 300°C, 270°C, and 250°C, respectively. Mechanisms of crystal formation were elucidated on the basis of gas chromatography-mass spectroscopy analysis, enabling the large-scale preparation of Fe3O4 nanocrystals. To provide an environmentally benign route, Fe3O4 nanocrystals were prepared with recycled solvent which was recovered from the initial experiment. The resulting porous Fe3O4 nanocrystals had larger average sizes than those of the initial nanocrystals. Structural characterization was performed using transmission electron microscopy and powder X-ray diffraction. [ABSTRACT FROM AUTHOR]

In this study, thin film encapsulation (TFE) with an Ag thin film is proposed to improve the long-term reliability of flexible displays in terms of the barrier property, flexibility, and heat dissipation. By applying thin film encapsulation to bottom-emission organic light-emitting diodes (BEOLEDs) fabricated on glass, the lifetimes of OLED devices were improved, showing differences among TFE layers. The maximum temperatures measured from the backside of the glass substrate were 66.73, 64.15, 59.21 and 39.63 °C after the OLED was operated at a luminance of 10000 cd/m2, and an operational lifetime test results were remarkably consistent with the measurement results of infrared images. Efficient heat dissipation through thermally conductive TFE layers improved the OLED reliability in terms of lifetime. [ABSTRACT FROM AUTHOR]

We report a compact all-optical side-firing probe directly ablated on a mode-expanded hybrid fiber end using a high-precision femtosecond laser processing technique. A segment of coreless silica fiber was adopted to achieve a large beam size and manipulation of the far field divergence angle. The radiating beam properties of the side-firing tip have been experimentally investigated and compared with numerical simulations. [ABSTRACT FROM PUBLISHER]

A simple and compact lensed dual-fiber probe having high collection efficiency for fluorescence signal is demonstrated. A lensed dual-fiber probe, composed of two parallel fibers and a common focusing lens, was simply implemented by the electric arc discharge method. The performance of the proposed probe was evaluated experimentally by measuring the reflection powers and fluorescence spectra of well-known targets and a fresh ginkgo leaf. The experimental result shows that the proposed probe provides a six-fold increase in the collection efficiency compared to measurements without the lens. In addition, the signal collection occurs very close to the probe surface with a suitably localized depth. [ABSTRACT FROM PUBLISHER]

In this study, a portable and large-area blackbody system was developed following a series of processes including design, computational analysis, fabrication, and experimental analysis and evaluation. The blackbody system was designed to be lightweight (5 kg), and its temperature could exceed the ambient temperature by up to 15 °C under operation. A carbon-fiber-based heat source was used to achieve a uniform temperature distribution. A heat shield fabricated from an insulation material was embedded at the opposite side of the heating element to minimize heat loss. A prototype of the blackbody system was fabricated based on the design and transient coupled electro-thermal simulation results. The operation performance of this system, such as the thermal response, signal transfer function, and noise equivalent temperature difference, was evaluated by employing an infrared imaging system. In addition, emissivity was measured during operation. The results of this study show that the developed portable and large-area blackbody system can be expected to serve as a reliable reference source for the calibration of aerial infrared images for the application of aerial infrared techniques to remote sensing. [ABSTRACT FROM AUTHOR]

The plasmonic photothermal (PPT) characteristics of gold nanostructures have been extensively investigated theoretically and experimentally due to their potential for use materials science and industry. The management of the size and shape of gold nanoparticles has been a key issue in the development of better solutions for PPT heat generation because their size and shape determine their resultant photothermal properties. However, the light absorption of gold nanostructures is mainly dependent on the wavelength and orientation of the incident light; hence, maintaining uniform size and shape is critical for achieving maximum photothermal energy. Morphologically homogeneous spherical gold nanoparticles, or super gold nanospheres prepared by slowly etching uniform octahedral gold nanoparticles, demonstrate better PPT heat generation compared with commercially available nonsmooth gold nanoparticles (GNSs). The PPT heating experiments show a maximum temperature difference of 5.7 °C between the super and ordinary GNSs with the same average maximum Feret's diameters, which result from the more efficient PPT heat power generation (20.6%) of the super GNSs. In an electromagnetic‐wave simulation, the super GNSs show lower polarization dependence and a 24.6% higher absorption cross‐section than ordinary GNSs. [ABSTRACT FROM AUTHOR]

Anti-reflection coatings (ARCs) from the cornea nipple array of the moth-eye remarkably suppress the Fresnel reflection at the interface in broadband wavelength ranges. ARCs on flat glass have been studied to enhance the optical transmittance. However, little research on the implementation of ARCs on curved optical lenses, which are the core element in imaging devices, has been reported. Here, we report double-sided, bio-inspired ARCs on bi-convex lenses with high uniformity. We theoretically optimize the nanostructure geometry, such as the height, period, and morphology, since an anti-reflection property results from the gradually changed effective refractive index by the geometry of nanostructures. In an experiment, the transmittance of an ARCs lens increases up to 10% for a broadband spectrum without distortion in spot size and focal length. Moreover, we demonstrate ~30% improved transmittance of an imaging system composed of three bi-convex lenses, in series with double-sided ARCs (DARCs). [ABSTRACT FROM AUTHOR]

Background: Recently, a combination of photodynamic therapy (PDT) and photothermal therapy (PTT) to generate reactive oxygen species (ROS) and heat to kill cancer cells, respectively has attracted considerable attention because it gives synergistic effects on the cancer treatment by utilizing the radiation of nontoxic low-energy photons such as long wavelength visible light and near IR (NIR) penetrating into subcutaneous region. For the effective combination of the phototherapies, various organic photosensitizer-conjugated gold nanocomplexes have been developed, but they have still some disadvantages due to photobleaching and unnecessary energy transfer of the organic photosensitizers. Results: In this study, we fabricated novel inorganic phototherapeutic nanocomplexes (Au NR–TiO2 NCs) by conjugating gold nanorods (Au NRs) with defective TiO2 nanoparticle clusters (d-TiO2 NP clusters) and characterized their optical and photothermal properties. They were observed to absorb a broad range of visible light and near IR (NIR) from 500 to 1000 nm, exhibiting the generation of ROS as well as the photothermal effect for the simultaneous application of PDT and PTT. The resultant combination of PDT and PTT treatments of HeLa cells incubated with the nanocomplexes caused a synergistic increase in the cell death compared to the single treatment. Conclusion: The higher efficacy of cell death by the combination of PDT and PTT treatments with the nanocomplexes is likely attributed to the increases of ROS generation from the TiO2 NCs with the aid of local surface plasma resonance (LSPR)-induced hot electrons and heat generation from Au NRs, suggesting that Au NR–TiO2 NCs are promising nanomaterials for the in vivo combinatorial phototherapy of cancer. [ABSTRACT FROM AUTHOR]

We present a design of a bilayer porous film structure on a glass substrate for the highly efficient ultraviolet (UV) protection with high visible-light transparency. To effectively block UVB (280–315 nm) and UVA (315–400 nm), titanium dioxide (TiO2) and zinc oxide (ZnO) are used as absorbing layers having the appropriate coverages in different UV ranges with extinction coefficients, respectively. We show the process of refractive index (RI) matching by controlling porosity (Pr). Effective RIs of porous media with TiO2 and ZnO were calculated based on volume averaging theory. Transmittances of the designed films with different effective RIs were calculated using rigorous coupled-wave analysis method. Using admittance loci method, the film thickness was optimized in center wavelengths from 450 to 550 nm. The results show that the optimal design provides high UV shielding performance at both UVA and UVB with high transparency in the visible range. We also analyze electrical field distributions in each layer and angle dependency with 3D HSV color map. [ABSTRACT FROM AUTHOR]

• SWCNT/AgNW transparent heater (TH) having long-term working stability was fabricated. • Overheating at NW junction due to Joule heating resulted in NW disconnections. • Dense SWCNT coating on AgNW film enhanced the heating performance of AgNW TH. • SWCNT film worked as a fast thermal dissipation layer in the hybrid film. • Our approach can be applicable to improve long-term stability for AgNW-based THs. A flexible silver nanowire transparent heater (AgNW TH) was recently reported. However, the fabrication of AgNW THs that are durable over the long term is an important concern due to nanowire thermal instability. In this work, a thin AgNW film was coated with a dense single-walled carbon nanotube (SWCNT) film on glass and polyimide (PI) substrates. This simple hybrid heater was evaluated for heater performance and long-term working stability. The AgNW TH dried in air was unstable and failed more rapidly at elevated temperatures under Joule heating than that dried in vacuum. The AgNW TH had the same temperature limit irrespective of nanowire coating density due to the low melting point of AgNWs. The SWCNT/AgNW TH displayed a higher heating temperature and longer working stability than the AgNW TH. Based on thermoreflectance imaging and considering a power balance model, the improved thermal stability of the hybrid heater is attributed to thermal uniformity, in turn related to fast heat dissipation via heat transfer pathways of the dense SWCNT film, which delayed deformation and disconnection of the AgNWs. This simple hybrid structure could enhance the long-term working stability of AgNW-based THs in a wide range of practical applications. [ABSTRACT FROM AUTHOR]