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Sensitive and Reproducible Gold SERS Sensor Based on Interference Lithography and Electrophoretic Deposition
摘要： Surface-enhanced Raman spectroscopy (SERS) is a promising analytical tool due to its label-free detection ability and superior sensitivity, which enable the detection of single molecules. Since its sensitivity is highly dependent on localized surface plasmon resonance, various methods have been applied for electric ?eld-enhanced metal nanostructures. Despite the intensive research on practical applications of SERS, fabricating a sensitive and reproducible SERS sensor using a simple and low-cost process remains a challenge. Here, we report a simple strategy to produce a large-scale gold nanoparticle array based on laser interference lithography and the electrophoretic deposition of gold nanoparticles, generated through a pulsed laser ablation in liquid process. The fabricated gold nanoparticle array produced a sensitive, reproducible SERS signal, which allowed Rhodamine 6G to be detected at a concentration as low as 10?8 M, with an enhancement factor of 1.25 × 105. This advantageous fabrication strategy is expected to enable practical SERS applications.
关键词： laser interference lithography,electrophoretic deposition,gold nanoparticle array,surface enhanced Raman spectroscopy,pulsed laser ablation in liquid
更新于2025-09-10 09:29:36
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Bulk and surface characterisation of micrometer-thick cobalt ferrite films grown by IR PLD
摘要： We have studied micrometer-thick cobalt ferrite films deposited on Si (100) single crystal substrates by nanosecond pulsed laser deposition at 1064 nm.The thickness of the deposited films (1.3 μm) was monitored by AFM. The chemical and structural characterisation of the films was carried out by Raman spectroscopy and transmission M?ssbauer spectroscopy at 300 and 26 K. For comparison purposes, transmission M?ssbauer data at these two temperatures were also recorded from a commercial cobalt ferrite powder and the home-made target used to grow the films. The surface characterisation was performed by X-Ray Photoelectron Spectroscopy (XPS) and Integral Low Energy Electron Spectroscopy (ILEEMS). XPS showed Co and Fe to be present as Co2+ and Fe3+, as expected for cobalt ferrite. The Raman spectra showed the lines characteristic of cobalt ferrite. The M?ssbauer spectra, both in the transmission and backscattering modes, were fitted to two sextets whose hyperfine parameters are in good agreement with those expected from Fe3+ cations occupying the tetrahedral and octahedral sites in the spinel-related structure. No significant differences were observed in the relative areas of the two sextets in the transmission and ILEEMS spectra, suggesting that the cation distribution at the surface and the bulk are not too different. However, the relative areas of the two components changed drastically with temperature both in the spectra of the films as in those recorded from the cobalt ferrite standards. We discuss the possible origin of the evolution with temperature of those relative areas.
关键词： X-ray photoelectron spectroscopy,Raman spectroscopy,Cobalt ferrite,M?ssbauer spectroscopy,Pulsed laser deposition
更新于2025-09-10 09:29:36
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Surface micro-structuring of type 304 stainless steel by femtosecond pulsed laser: effect on surface wettability and corrosion resistance
摘要： This paper presents results on femtosecond (fs) pulsed laser-based surface micro-structuring of type 304 stainless steel (304 SS). Post laser treatment surface wettability and corrosion resistance investigation are reported. SS sample surfaces have been micro-structured using a typical laser fluence of ~ 0.9 J/cm2 for varying sample scanning speed in the range 25–1000 μm/s. Dense array of micro-protrusions have been generated without formation of a crater for an optimized target scan speed exceeding 200 μm/s. Static water contact angle (WCA) measurement indicated super-hydrophilic behavior immediately after laser treatment. However, hydrophilicity (wettability) was found to decrease with storage time with sample becoming highly hydrophobic (WCA: 144° ± 5°) within 50 days after laser treatment. Corrosion resistance of the laser-treated samples was measured by potentio-dynamic polarization technique. Fs laser micro-structured SS has shown poorer corrosion resistance in comparison to pristine surface. Observed poorer corrosion resistance of laser-treated surface has been explained on the basis of surface chemical composition and surface roughness. The results demonstrated that corrosion resistance increased with increasing hydrophobicity of the SS surface.
关键词： corrosion resistance,femtosecond pulsed laser,stainless steel,surface micro-structuring,wettability
更新于2025-09-10 09:29:36
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(TiO <sub/>2</sub> ) <sub/>1?x</sub> (TaON) <sub/>x</sub> Solid Solution for Band Engineering of Anatase TiO <sub/>2</sub>
摘要： Band engineering of anatase TiO2 was achieved by means of an anatase (TiO2)1?x(TaON)x (TTON) solid solution. Epitaxial thin films of TTON (0.1 ≤ x ≤ 0.9) were synthesized by nitrogen plasma-assisted pulsed laser deposition on (LaAlO3)0.3(SrAl0.5Ta0.5O3)0.7 substrates. Epitaxial growth of anatase TTON was confirmed by X-ray diffraction. The lattice constants of the TTON thin films increased with TaON content in accordance with Vegard’s law, indicating formation of a complete solid solution. The bandgaps, band alignment, and refractive indices of the TTON thin films were investigated by combination of spectroscopic ellipsometry and X-ray photoelectron spectroscopy. The bandgap of the anatase TTON systematically decreased with increasing x, mainly because of an upward shift in the valence band maximum caused by broadening of the valence band as a result of hybridization of the shallow N 2p orbital. The position of the conduction band minimum was rather insensitive to chemical composition, which makes the band alignment of anatase TTON suitable for photocatalytic water splitting with visible light. The refractive index of anatase TTON monotonically increased with an increase in x.
关键词： Epitaxial thin films,Vegard’s law,X-ray photoelectron spectroscopy,TTON solid solution,Band engineering,Photocatalytic water splitting,Spectroscopic ellipsometry,Nitrogen plasma-assisted pulsed laser deposition,Anatase TiO2
更新于2025-09-10 09:29:36
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Raising the Operating Temperature of (Ga,Mn)As/GaAs Spin Light Emitting Diodes by Applying Post-Growth Treatment
摘要： Spin light emitting diodes (spin-LEDs) containing (Ga,Mn)As ferromagnetic layers are fabricated based on InGaAs/GaAs heterostructures and studied. We achieve increases in the operating temperatures of our spin-LEDs by subjecting the surface of the structures, prior to depositing an ohmic metal contact, to pulsed laser annealing. The fabricated devices produce circularly polarized electroluminescence when placed in an external magnetic field. The temperatures at which circularly polarized electroluminescence is still observed is raised from 30 K for unprocessed structure to 110 K for laser-annealed structures. The observed effect is linked to an increase in the Curie temperature of the (Ga,Mn)As layer as a result of laser impact.
关键词： ferromagnetic layers,circularly polarized electroluminescence,Curie temperature,Mn)As,pulsed laser annealing,Spin light emitting diodes,(Ga
更新于2025-09-10 09:29:36
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The Study of Features of Formation and Properties of A3B5 Semiconductors Highly Doped with Iron
摘要： Layers of InAs, InSb, and GaSb semiconductors highly doped with iron during their growth by the method of pulsed laser deposition are studied experimentally. The best temperatures for layer formation on GaAs (100) substrates are: 250°C (InSb : Fe), 300°C (InAs : Fe), and 350°C (GaSb : Fe). At high Fe concentration (over 10 at %) the layers display ferromagnetic properties expressed in emergence of a hysteresis curve within the magnetic field dependences of the Hall resistance, negative magnetoresistance, and in some cases, ferromagnetic-type magnetization at measurements at room temperature. The atoms of iron do not change the type of layer conductivity; InAs : Fe and InSb : Fe layers possess n-type conductivity, and GaSb : Fe layers display p-type conductivity due to their intrinsic point defects.
关键词： Hall effect,A3B5 semiconductors,ferromagnetic properties,magnetoresistance,iron doping,pulsed laser deposition
更新于2025-09-09 09:28:46
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Nanoelectronics and Materials Development || Epitaxial Cu3Ge Thin Film: Fabrication, Structure, and Property
摘要： In this paper, the fabrication and electrical property characterization of epitaxial Cu3Ge thin film are performed. By adjusting deposition parameters, the crystallinity of the as‐grown Cu3Ge thin films is improved, with the formation of twins within it. The average work function of epitaxial Cu3Ge thin film is measured to be ～4.47 + 0.02 eV, render‐ ing it a desirable mid‐gap gate metal for applications in complementary metal‐oxide semiconductor (CMOS) devices. The present study therefore shows an epitaxial Cu3Ge thin film that is promising for applications.
关键词： sapphire,semiconductor metallization,Cu3Ge thin film,pulsed laser deposition,twin
更新于2025-09-09 09:28:46
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Nitric Oxide Detector Based on WO <sub/>3</sub> -1wt%In <sub/>2</sub> O <sub/>3</sub> -1wt%Nb <sub/>2</sub> O <sub/>5</sub> with State-of-the-Art Selectivity and ppb-Level Sensitivity
摘要： Fast, sensitive, and precise detection of nitric oxide (NO) is critical to many applications in environmental monitoring and early disease diagnosis via respiratory testing. An effective detection system requires a sensor to detect NO gas at the parts per billion (ppb) level, and this system should possess a high degree of anti-interference selectivity. To achieve these targets, a series of gas sensor thin films based on intrinsic WO3, one-additive-doped WO3 (prepared by doping In2O3 or Nb2O5), and two-additive-doped WO3 (synthesized by doping with In2O3 and Nb2O5) oxides were successfully grown. By analyzing the properties of sensitivity, selectivity, responsiveness, and recovery time of the gas sensors, we found that WO3-1wt%In2O3-1wt%Nb2O5 has overwhelming advantages over intrinsic WO3, WO3-In2O3, and WO3-Nb2O5. A sensing response value of 2.4 was observed for NO concentrations as low as 20 ppb from the WO3-1wt%In2O3-1wt%Nb2O5 sensor. With 100 ppb NO gas, the WO3-1wt%In2O3-1wt%Nb2O5 sensor achieved a high response of 56.1 at 70 °C, which is a state-of-the-art performance for NO detection at low working temperature settings. WO3-1wt%In2O3-1wt%Nb2O5 also yields significantly improved selectivity and stability over intrinsic WO3, WO3-In2O3, and WO3-Nb2O5. Studies on the sensing mechanism show that the grain size, rather than the n?n heterostructure effect, plays a dominant role in the observed results. By decreasing the grain size so that it is close to the thickness of the space-charge layer, the sensing response is enhanced. Although room remains to further improve the sensing properties, the performance of WO3-1wt%In2O3-1wt%Nb2O5 is sufficient for implementation in low-content NO detection devices.
关键词： codoping,high selectivity,NO gas sensor,limit of detection (LOD),ppb-level response,pulsed laser deposition (PLD)
更新于2025-09-09 09:28:46
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Effects of Laser Irradiation on a Copper Electrodeposition Process and Coating Quality
摘要： In this study, a hybrid pulsed laser and electrochemical processing technique was used to deposit a copper coating on a stainless steel substrate. The laser irradiation mechanism in the electrodeposition process was studied by detecting the mechanical and thermal effects. The electrodeposition samples were irradiated by lasers with varying single-pulsed energies and compared. The grains of the coating were observed with a scanning electron microscope (SEM), and the tensile strength and ductility were measured using a UTM4000 series electronic universal testing machine. The results showed that the deposition rate may be increased, and the coating quality may be improved by laser irradiation with the proper single-pulsed energy. This is due to an increase in the conductivity and diffusion coefficient of the solution, arising from an increase in the solution temperature and the local stirring induced by plasma bubbles. The grain size and growth direction of the dendrite are also affected by laser irradiation.
关键词： Electrodeposition,Deposition rate,Plasma shockwave,Coating quality,Pulsed laser
更新于2025-09-04 15:30:14