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Enhanced green emission from Er-doped (AlGa) <sub/>2</sub> O <sub/>3</sub> films grown by pulsed laser deposition
摘要： Erbium (Er) doped (AlGa)2O3 films were deposited on sapphire substrates using pulsed laser deposition. The transmittance spectra and X-ray photoelectron spectroscopy measurements show that transparent (AlGa)2O3:Er films with a wider bandgap can be achieved by increasing the Al content in the targets. All films exhibit the strongest pure green emission at 550 nm with the wavelength independent of the alloy compositions. A maximum intensity observed at Al content of 0.34 is several times higher than that in Ga2O3:Er films, indicating that the intensity of green emission can be enhanced by increasing the host bandgap. Our study also reveals that too high Al content has decreased the photoluminescence intensity, which should be related to the degraded crystallinity proved by X-ray rocking curve. These results suggest that (AlGa)2O3:Er film is a promising material for fabricating efficient green luminescent devices.
关键词： photoluminescence,bandgap,green emission,pulsed laser deposition,Er-doped (AlGa)2O3
更新于2025-09-23 15:21:01
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Effects of oxygen pressure on PLD-grown Be and Cd co-substituted ZnO alloy films for ultraviolet photodetectors
摘要： We report on the synthesis of Be and Cd co-substituted ZnO (BexCdyZn1?x?yO) quaternary alloy films on c-plane sapphire substrates by pulsed laser deposition. The results show that all deposited films exhibit single-phase wurtzite structure with a surface roughness less than 1.5 nm. By adjusting the O2 pressure during growth, the optical bandgap of the film is tuned from ~3.3 to ~3.52 eV. At 5 V bias, the BexCdyZn1-x-yO-based photodetector exhibits a remarkable photoresponse in the ultraviolet region with low dark current (~ 16.2 pA) and high detectivity (9.31· 1010 Jones). The rise and decay times of the photodetectors based on BexCdyZn1-x-yO (order of seconds) are clearly faster than those based on pure ZnO (order of minutes). Higher O2 pressure results in better crystalline quality of BexCdyZn1-x-yO film and thus lower dark current and faster photoresponse in the device due to the decrease of oxygen vacancy-related defects under oxygen-rich growth conditions. These results indicate that oxygen pressure plays an important role in the growth of high-quality BexCdyZn1-x-yO alloy films, which have great potential in fabricating high-performance ultraviolet photodetectors.
关键词： Bandgap engineering,BexCdyZn1-x-yO alloys,UV photodetectors,Pulsed laser deposition
更新于2025-09-23 15:21:01
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Surface Bubble Growth in Plasmonic Nanoparticle Suspension
摘要： Understanding the growth dynamics of the microbubbles produced by plasmonic heating can benefit a wide range of applications like microfluidics, catalysis, micro-patterning and photo-thermal energy conversion. Usually, surface plasmonic bubbles are generated on plasmonic structures pre-deposited on the surface subject to laser heating. In this work, we investigate the growth dynamics of surface microbubbles generated in plasmonic nanoparticle (NP) suspension. We observe much faster bubble growth rates compared to those in pure water with surface plasmonic structures. Our analyses show that the volumetric heating effect around the surface bubble due to the existence of NPs in the suspension is the key to explain this difference. Such volumetric heating increases the temperature around the surface bubble more efficiently compared to surface heating which enhances the expelling of dissolved gas. We also find that the bubble growth rates can be tuned in a very wide range by changing the concentration of NPs, besides laser power and dissolved gas concentration.
关键词： bubble growth dynamics,plasmon resonance,gold nanoparticles (NPs),volumetric heating,micro-bubbles,pulsed laser,photothermal
更新于2025-09-23 15:21:01
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Optical properties of diamond-like carbon films prepared by pulsed laser deposition onto 3D surface substrate
摘要： It is difficult to grow uniform film by pulsed laser deposition because the spatial distribution of the laser-induced plume is a forward-directed cone-shape. A 3D-motional deposition setup was founded, and the correlative mathematical model of the film thickness on the 3D curved surface was deduced. Based on simulation and optimization, the diamond-like carbon (DLC) film was grown onto the large curved silicon substrate. According to the infrared transmittance spectra, the optical constants of the DLC film samples at different regions on the curved substrate were similar, indicating that the DLC film prepared onto the curved surface was homogeneous. Meanwhile, the deviation of average transmittance in the medium infrared band was below 2.3%, which could improve the imaging performance of the infrared detection. This research is useful to expand the application of the pulsed laser deposition in the optical field.
关键词： uniform transmittance,Raman spectroscopy,3D curved surface,Pulsed laser deposition,DLC film,infrared spectrum
更新于2025-09-23 15:21:01
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The relation between magnesium evaporation and laser absorption and weld penetration in pulsed laser welding of aluminum alloys: Experimental and numerical investigations
摘要： It is observed that in laser welding of aluminum alloys, magnesium can evaporate, and the weld penetration is dependent on Mg content of the alloy and Mg loss from the weld pool. In this research, it is proposed that the presence of Mg not in the base metal alloy, but rather the presence of Mg vapor in the plasma plume over the weld pool affects the laser absorption, and it is through this phenomenon that the weld profile and penetration is affected. Numerical simulation was performed to determine the relationship between the weld profile to estimate the effective laser absorption coefficient of four Al alloys and in parallel EPMA technique was used to determine the Mg losses of the weld metals. The combined analysis of the results showed that increasing the laser pulse energy (decreasing laser pulse frequency), Mg evaporation is increased, and that, in turn, increased the effective laser absorption coefficient. However, more laser power absorption does not necessarily mean more weld penetration. Laser absorption results in weld penetration, once the threshold Mg evaporation rate of 200 × ?10 6g/cm2 is passed.
关键词： Pulsed laser welding,Effective absorption coefficient,Aluminum alloys,Evaporation,Magnesium content,Penetration depth
更新于2025-09-23 15:21:01
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Analytical solution of dual-phase-lag based heat transfer model in ultrashort pulse laser heating of A6061 and Cu3Zn2 nano film
摘要： The dual-phase-lag model provides the best performance among many existing non-Fourier models and it is particularly more suitable for a short duration of heating. The present literature survey certifies the availability of very few research papers specifically on the development of an exact analytical solution of the dual-phase-lag model illustrating the thermal analysis of ultrashort pulsed laser heating. To address such issues, the present work is intended to develop an exact solution of the thermal response based on the dual-phase-lag heat conduction model utilized for the femtosecond laser heating of nanofilm. The corresponding solution has been derived by a hybrid application of the Duhamel’s theorem and the finite integral transform approach. A comparative thermal analysis has been depicted for the laser heating of 5 nm thin A6061 and Cu3Zn2 nanofilm and the necessity of non-Fourier analysis over the Fourier’s model has been justified. Existing research works are mostly based on gold and chromium nanofilm. As multi-component microstructures of Cu and Al are scientifically proved to be excellent metallic properties (magnetic and optical) and exhibit strong response during energy driven-chemical reactions, the present analysis is focused on these two materials for the femtosecond laser irradiation. In the present analysis, optical properties (absorptivity and reflectivity) of substrate material have been taken into account to develop a better and realistic analytical model than the existing models. The research output notifies that at 0.1 ps of the laser pulse and 100 J m?2 of the laser intensity, developed temperature history reaches the melting point temperature of both the materials in combination with other thermophysical properties. The mathematical modeling also provides the appropriate information about the selection of thermal relaxation time lags for respective materials and this also justifies the experimental observation of relaxation time lags as reported in the literature. The thermal response has been captured for both A6061 and Cu3Zn2 material along the various depths of the nanofilm to evolve the irradiation capacity of the pulsed femtosecond laser source. The present research output is well validated through numerical and experimental research works of existing literature with a negligible variation. The inclusion of optical properties of materials in the present research work plays an important role as it is noticed that the maximum deviation of the temperature difference between with and without optical properties is evidenced as 38.86% and 57.70% for A6061 and Cu3Zn2 nanofilms, respectively.
关键词： Analytical solution,Dual-phase-lag model,Optical properties,Thermal response,Ultrafast pulsed laser
更新于2025-09-23 15:21:01
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Hierarchical core-shell tungsten oxide/TiO2 nanowires as an effective photocatalyst
摘要： In this letter, tungsten oxide(WO3)/TiO2 core-shell nanowires were prepared by depositing a layer of TiO2 nanoparticles on the surface of WO3 nanowires via a pulse laser deposition method. These TiO2 nanoparticles are qusi-aligned wire-like structure on the surface of WO3 nanowires. The number of laser pulses during the deposition adjusts the TiO2 thickness. When used as photocatalyst, these core-shell nanowires have photocatalytic activity in the degradation of rhodamine B (RhB). The photo-induced electron-hole separation effect between WO3 and TiO2 contributes to the improvement of the photocatalystic activity. This makes these nanowire arrays having good potential in wastewater treatment.
关键词： Pulsed laser deposition,Nanocomposites,Semiconductors
更新于2025-09-23 15:21:01
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Laser-generated plasmas in length scales relevant for thin film growth and processing: simulation and experiment
摘要： In pulsed laser deposition, thin film growth is mediated by a laser-generated plasma, whose properties are critical for controlling the film microstructure. The advent of 2D materials has renewed the interest in how this ablation plasma can be used to manipulate the growth and processing of atomically thin systems. For such purpose, a quantitative understanding of the density, charge state, and kinetic energy of plasma constituents is needed at the location where they contribute to materials processes. Here, we study laser-induced plasmas over expansion distances of several centimeters from the ablation target, which is the relevant length scale for materials growth and modification. The study is enabled by a fast implementation of a laser ablation/plasma expansion model using an adaptive Cartesian mesh solver. Simulation outcomes for KrF excimer laser ablation of Cu are compared with Langmuir probe and optical emission spectroscopy measurements. Simulation predictions for the plasma-shielding threshold, the ionization state of species in the plasma, and the kinetic energy of ions, are in good correspondence with experimental data. For laser fluences of 1–4 J cm?2, the plume is dominated by Cu0, with small concentrations of Cu+ and electrons at the expansion front. Higher laser fluences (e.g. 7 J cm?2) lead to a Cu+ -rich plasma, with a fully ionized leading edge where Cu2+ is the dominant species. In both regimes, simulations indicate the presence of a low-density, high-temperature plasma expansion front with a high degree of ionization that may play a significant role in doping, annealing, and kinetically-driven phase transformations in 2D materials.
关键词： pulsed laser deposition,plasma diagnostics,plasma processing of 2D materials,laser plasma simulation,2D materials,laser ablation,plasma assisted processing
更新于2025-09-23 15:19:57
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Plasma charging effect on the nanoparticles releasing from the cavitation bubble to the solution during nanosecond Pulsed Laser Ablation in Liquid
摘要： The laser induced plasma during the nanosecond Pulsed Laser Ablation in Liquid (PLAL) plays a crucial role in the nanoparticles (NPs) formation and charging. It was demonstrated that during the plasma phase evolution, once the NPs are formed, they are charged with the excess of plasma electrons. Immediately after the plasma phase extinguishes, the NPs will be released in the induced vapor bubble, generated by the fast energy exchanges between the plasma and the liquid. The excess of charge in the NPs preserves them from the agglomeration during the bubble evolution and can induces an electrostatic pressure able to eject the particles outside the cavitation bubble. In this work, the plasma charging effect on the particle releasing in solution, during the bubble evolution, has been investigated. Temporal evolution of laser induced bubble on silver target immersed in water has been measured with the shadowgraph technique. Then, starting from the experimental bubble radius evolution, the releasing of the NPs from the cavitation bubble to the liquid has been modeled by comparing the electrostatic pressure of the charged NPs cloud and the pressure of the cavitation bubble. The following discussion proposes a new insight of the mechanism of NPs releasing in solution.
关键词： Laser Ablation Synthesis in Solution (LASIS),Cavitation bubble,NPs releasing,Pulsed Laser Ablation in Liquid (PLAL),NP formation
更新于2025-09-23 15:19:57
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Optical control of layered nanomaterial generation by pulsed-laser ablation in liquids
摘要： Pulsed-laser ablation in liquids capitalizes on combining chemical and optical control to rapidly generate size, composition, and phase-controlled nanostructures, without the need for surfactants. Very high temperatures, which we determined to be ca. (8,400 ± 1,300) K, pressures, and ion densities exist in the laser-induced liquid-confined plasma. These unique conditions, coupled with the rapid cooling during which nanoparticles are formed, permitted access to new extreme regions of materials’ phase diagrams. This way, we produced metastable layered copper and zinc hydroxide-based nanocrystals with interesting physical properties that can serve as precursors for two-dimensional inorganic semiconductor nanomaterials.
关键词： LTE spectra,optical control,electron temperature,layered nanocrystals,Pulsed-laser ablation in liquids,laser-induced plasma
更新于2025-09-23 15:19:57