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Laser transmission welding and surface modification of graphene film for flexible supercapacitor applications
摘要： When a graphene ?lm is coated onto a ?exible polymer substrate, weak adhesion can cause delamination of the ?lm under mechanical bending. Moreover, as each graphene layer restacks, the performance of the ?lm as an electrode for a supercapacitor becomes limited. In this study, facile laser welding and surface modi?cation processes are demonstrated to overcome these limitations. First, a continuous wave laser beam is applied to the interface between the coated graphene and the underlying transparent polycarbonate substrate. This welding process signi?cantly improves their adhesion and enables excellent mechanical bendability. Second, surface modi?cation of graphene is achieved under ambient conditions by irradiating the graphene ?lm surface with a nanosecond pulsed laser. Sandwich-type supercapacitors are fabricated using these surface-modi?ed graphene electrodes with a PVA-H3PO4 electrolyte. The e?ect of the laser ?uence on the performance of the supercapacitor is investigated. At an optimal laser power, an areal capacitance of 4.7 mF/cm2 is achieved.
关键词： Laser transmission welding,Graphene,Flexible device,Supercapacitor,Pulsed laser
更新于2025-11-25 10:30:42
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Crystallographically oriented porous ZnO nanostructures with visible-blind photoresponse: controlling the growth and optical properties
摘要： We have grown catalyst-free crystallographically oriented porous ZnO nanostructures by pulsed laser deposition (PLD) method. The deposition was performed in two stages for each sample. In the first stage, self-seeding of ZnO was performed on the quartz substrate, and the angle of deposition (seeding-angle) was varied. Thus, the growth of seeds is different here. In the second stage, the deposition was performed at a glancing angle (at 85?) for the fixed duration of time to grow the nanostructures. These PLD-grown nanostructures acquire highly oriented wurtzite structure. We find that the seeding-angle during the first stage is the determining deposition parameter which influences the growth and other properties of these nanostructures in a controllable manner. The variation in seeding-angle systematically tunes the crystallographic orientation and porosity, which in turn influences the visible-blindness and ultraviolet (UV) photoresponse of these nanonetworks. Here we report the growth of completely defect-free crystallographically oriented nanostructures with necessary porosity for application in visible-blind UV photodetection.
关键词： Crystalline ZnO,catalyst-free ZnO,glancing angle deposition (GLAD),seeding,pulsed laser deposition (PLD),nanostructures
更新于2025-11-21 11:03:13
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Controlling porosity and ultraviolet photoresponse of crystallographically oriented ZnO nanostructures grown by pulsed laser deposition
摘要： We have synthesized a series of porous nanostructures of c-axis oriented wurtzite ZnO using glancing angle pulsed laser deposition. During deposition, the oxygen partial pressure (PO2) was varied to study the effects on growth, porosity and optical properties. With varied PO2 the growth of nanostructure changes gradually without losing its crystallographic orientation. The variation in PO2 causes systematic change in porosity of these nanostructures, which strongly influences ultraviolet photoresponse. These results show that the parameters such as surface morphology, growth and porosity as well as the optoelectronic properties can be controlled by variation in PO2 without compromising the crystalline structure.
关键词： Crystalline nanostructures,Photoresponse,Porosity,Ultraviolet,Glancing angle pulsed laser deposition
更新于2025-11-19 16:56:42
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Near-infrared-light-triggered photoelectrochemical biosensor for detection of alpha-fetoprotein based on upconversion nanophosphors
摘要： A novel photoelectrochemical (PEC) biosensor based on hybrids of NaYF4:Yb, Tm， zinc oxide (ZnO) and cadmium sulfide (CdS) was constructed to detect alpha-fetoprotein (AFP), which possesses the advantages of low background noise and non-damage to the biological substance. Herein, we prepared NaYF4:Yb,Tm/ZnO/CdS composite film electrode by pulsed laser deposition. The selected materials of ZnO and CdS can make full use of the upconversion luminescence (~360nm, ~480nm) of NaYF4:Yb,Tm nanophosphors under 980nm laser excitation. Meanwhile, an effective matching of energy levels between the conduction bands of CdS and ZnO can prompt photoelectrochemical performance of the electrode. The biosensor shows ultrasensitive detection of AFP with a wide linear range from 0.01 ng mL-1 to 200 ng mL-1 and a low detection limit of 5 pg mL-1. Therefore, the proposed PEC biosensor based on upconversion nanophosphors is potentially attractive for achieving excellent photoelectrochemical biosensor for detection of other cancer markers in clinical analysis.
关键词： photoelectrochemical,pulsed laser deposition,upconversion luminescence,near-infrared light-triggered biosensor
更新于2025-11-14 15:27:09
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Structural, electronic and optical properties of pulsed laser deposited Cu2SnS3 photo absorber thin films: A combined experimental and computational study
摘要： Pulsed laser deposited thin films of Cu2SnS3 (CTS) are characterized for the structural, electronic and optical properties using X-ray diffraction, Raman, UV–Vis-NIR spectroscopy, scanning electron microscopic techniques, and density functional theory. It is observed that thin-film samples annealed at low temperature have a metastable tetragonal structure, whereas the films annealed at 450 °C have a predominant stable monoclinic phase. A direct band gap of 1.1 eV, measured from the transmittance spectra, in close agreement with the theoretical band gap value of 0.89 eV obtained from density functional theory calculations. Optical properties reveal that CTS has a large absorption coefficient ~0.5 × 104 cm?1 at 1.5 eV which is comparable to other CuS based materials like CuInS2 and Cu2ZnSnS4. The direct band gap and large absorption coefficient make CTS as one of the potential alternative absorber materials for thin-film solar cell applications.
关键词： Annealing,Raman spectroscopy,Thin films,Density functional theory,Pulsed laser deposition,Optical properties
更新于2025-10-22 19:40:53
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Synthesis of Bi <sub/>2</sub> O <sub/>3</sub> films, studying their optical, structural, and surface roughness properties
摘要： Reactive pulse laser deposition system was used to prepare Bi2O3 thin films at different laser fluence. It effect on the physical properties of thin films was investigated. A Polymorphous structure was obtaining from XRD results. While the obtained microscopic results from AFM show that grain size is varied between 33.48nm and 131.6 nm. The estimated band gap value from the optical transmission found to range from 1.7-2.9 eV.
关键词： Pulsed laser deposition,morphological properties,Optical properties,Bismuth trioxide,structural properties
更新于2025-09-23 15:23:52
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Electroresistance of Pt/BaTiO<sub>3</sub>/LaNiO<sub>3</sub> ferroelectric tunnel junctions and its dependence on BaTiO<sub>3</sub> thickness
摘要： Recently, ferroelectric tunnel junctions (FTJs) have attracted considerable attention due to their great potential in next generation non-volatile memories. In this work, we report on thickness-dependent tunneling electroresistance (TER) and corresponding evolution of transport behavior in Pt/BaTiO3/LaNiO3 FTJs with various BaTiO3 thicknesses of 2.0, 3.2, and 4.8 nm. The TER effect is observed in the 3.2 nm-thick Pt/BaTiO3/LaNiO3 tunnel junction and an ON/OFF current ratio of ~170 is achieved due to the modulation of barrier height by polarization reversal. When the BaTiO3 is increased to 4.8 nm in thickness, the ferroelectric-modulation of the barrier profile becomes more pronounced and the dominant transport mechanism changes from electron tunneling to thermally-activated thermionic injection. As a result, the OFF state current is significantly reduced due to the suppression of the Fowler-Nordheim tunneling with increased width and height of the BaTiO3 barrier. A greatly improved ON/OFF current ratio of ~12500 is thus achieved in the 4.8 nm-thick Pt/BaTiO3/LaNiO3 FTJ device. These results facilitate deeper understanding of the TER effects from the viewpoint of not only the barrier profile but also the transport mechanism.
关键词： Pulsed laser deposition,Ferroelectric tunnel junctions,Ferroelectric memory,Resistive switching
更新于2025-09-23 15:23:52
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Spectral analysis for photoacoustic pressure sensor designs: Theoretical model improvement and experimental validation
摘要： In the pulsed laser photoacoustic (PA) detection and spectroscopy applications, the fundamental frequency of the PA signal produced, and the sensor resonance frequency should be as close as possible to each other so that analyzes from the obtained signals can be performed effectively. In order to determine the fundamental frequency of the PA wave, a theoretical model approach based on the development of the frequency domain solution of the PA wave equation is presented for use in the PA pressure sensor designs. For the validation of the theoretical model approach, a PA experimental setup was established, and measurements were made in distilled water. The theoretical and experimental PA frequency spectra were determined to be very compatible with each other. Thus, the theoretical model approach was experimentally validated. According to the theoretical model approach, fundamental frequency values obtained from the experimental measurement results were determined with an average accuracy of ? 4.212%. Furthermore, it has been determined that this value has fallen to ?0.267% in the measurements. With the obtained results from the theoretical model approach, we propose that PA pressure sensors with the more selective and narrower band can be designed for more sensitive detection. Moreover, in this study the effects of different laser parameters such that pulse duration, and laser beam width, on the spectral content of the obtained PA signal are analyzed. These analyses will shed light on the vision of acoustic pressure sensor design by helping to select the most optimum parameters for PA detection.
关键词： Theoretical model approach,Photoacoustic wave equation,Acoustic pressure sensor,Frequency domain solution,Pulsed laser photoacoustic method,Spectroscopy
更新于2025-09-23 15:23:52
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Oxynitride Thin Films versus Particle-Based Photoanodes: a Comparative Study for Photoelectrochemical Solar Water Splitting
摘要： The solar water splitting process assisted by semiconductor photocatalysts attracts growing research interests worldwide for the production of hydrogen as a clean and sustainable energy carrier. Due to their optical and electrical properties several oxynitride materials show great promise for the fabrication of efficient photocatalysts for solar water splitting. This study reports a comparative investigation of particle- and thin films-based photocatalysts using three different oxynitride materials. The absolute comparison of the photoelectrochemical activities favors the particle-based electrodes due to the better absorption properties and larger electrochemical surface area. However, thin films surpass the particle-based photoelectrodes due to their more suitable morphological features that improve the separation and mobility of the photo-generated charge carriers. Our analysis identifies what specific insights into the properties of materials can be achieved with the two complementary approaches.
关键词： Oxynitride,pulsed laser deposition,photoelectrochemistry,thin films,solar water splitting,photoanode
更新于2025-09-23 15:23:52
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Reduced Graphene Oxide-Nanostructured Silicon Photosensors With High Photoresponsivity at Room Temperature
摘要： We have created nanostructured Si (~3 nm) with a direct band gap of 1.37 eV on electrically conducting reduced graphene oxide (rGO) for a highly efficient photosensor. This robust photosensor is fabricated using a non-equilibrium processing route, where nanosecond excimer laser pulses melt the alternating layers of Si and amorphous carbon to form micropillars and nanoreceptors of Si on rGO layers. The incident white light generates free carriers in the Si microstructures and nanoreceptors which are ballistically transported (via rGO layers) to the external circuit under the application of a voltage bias. The responsivity of rGO-Si devices to light (resistance vs time) and I-V measurements indicate an exponential drop in resistance with the incidence of white light and non-rectifying nature, respectively. Photoresponsivity of the rGO-Si devices is calculated to be 3.55 A/W at room temperature, which is significantly larger than the previously fabricated graphene-based Ohmic photosensors. Temperature-dependent resistance measurements of rGO-Si structures follow Efros-Shklovoskii variable range hopping (ES-VRH) electrical conduction in the low-temperature region (<100 K) and Arrhenius conduction in the high-temperature region (>100 K). In rGO, the localization length, hopping energy, and activation energy are calculated to be 17.58 μm, 3.15 meV, and 1.67 meV, respectively. The 2D nature of highly reduced and less defective rGO also render an interesting negative magnetoresistance (~2.5 %) at 5 K, thereby indicating potential implications of rGO-Si in opto-spintronics. The large-area integration of rGO-Si structures with sapphire employing nanosecond pulsed laser annealing and its exciting photosensing properties will open a new frontier for further extensive research in these functionalized 2D materials.
关键词： Pulsed laser annealing,Raman spectroscopy,Variable range hopping,Nanostructures,Reduced graphene oxide
更新于2025-09-23 15:22:29