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Pulsed Laser-Assisted Helium Ion Nanomachining of Monolayer Graphene—Direct-Write Kirigami Patterns
摘要： A helium gas ?eld ion source has been demonstrated to be capable of realizing higher milling resolution relative to liquid gallium ion sources. One drawback, however, is that the helium ion mass is prohibitively low for reasonable sputtering rates of bulk materials, requiring a dosage that may lead to signi?cant subsurface damage. Manipulation of suspended graphene is, milling. We demonstrate that competitive ion beam-induced therefore, a logical application for He deposition from residual carbonaceous contamination can be thermally mitigated via a pulsed laser-assisted He milling. By optimizing pulsed laser power density, frequency, and pulse width, we reduce the carbonaceous byproducts and mill graphene gaps down to sub 10 nm in highly complex kiragami patterns.
关键词： pulsed laser,nanopatterning,graphene,direct-write kirigami
更新于2025-09-11 14:15:04
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Gyrotropic slab waveguide coupled silica microfiber-based magnetic field sensor
摘要： By controlling the polarization direction of BaTiO3 (BTO) layer, the nonvolatile and reversible resistive switching behavior of the BaTiO3/La0.7Sr0.3MnO3 (BTO/LSMO) layered heterostructure have been observed. Pulsed laser deposition (PLD) technique was used to prepare it on the (001) oriented single-crystal SrTiO3 (STO) substrate, and its magnetic and electric properties were studied. Moreover, the change of the resistivity and metal-insulator transition temperature (TMI) for the LSMO layer were found to be induced by the switching of the electric field direction. The resistivity is decreased while the TMI is increased for the accumulation state of hole carriers when a negative electric field is applied to the BTO layer. By contrast, the resistivity is increased while the TMI is decreased for the depletion state of hole carriers when a positive electric field is applied to the BTO layer. This result indicates a nonvolatile and reversible resistive switching behavior in the multiferroic heterostructure control through the external electric field on ferroelectric layer, which provides a platform to develop unique electronic devices, such as nonvolatile random-access memories, sensors and memristive devices, etc.
关键词： multiferroic heterostructure,resistive switching behavior,pulsed laser deposition,nonvolatile random-access memories
更新于2025-09-11 14:15:04
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Application of Two-Photon-Absorption Pulsed Laser for Single-Event-Effects Sensitivity Mapping Technology
摘要： Single-event effects (SEEs) in integrated circuits and devices can be studied by utilizing ultra-fast pulsed laser system through Two Photon Absorption process. This paper presents technical ways to characterize key factors for laser based SEEs mapping testing system: output power from laser source, spot size focused by objective lens, opening window of Pockels cell, and calibration of injected laser energy. The laser based SEEs mapping testing system can work in a stable and controllable status by applying these methods. Furthermore, a sensitivity map of a Static Random Access Memory (SRAM) cell with a 65 nm technique node was created through the established laser system. The sensitivity map of the SRAM cell was compared to a map generated by a commercial simulation tool (TFIT), and the two matched well. In addition, experiments in this paper also provided energy distribution pro?le along Z axis that is the direction of the pulsed laser injection and threshold energy for different SRAM structures.
关键词： pulsed laser,SRAM,single event effect,sensitive mapping,two photon absorption
更新于2025-09-11 14:15:04
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Sterilization for Bacillus Subtilis var. natto by Low Pressure Sputtering and Laser Ablation Plasma using Metal Powder Target
摘要： Effect of plasma sterilization for bacillus subtilis var. natto was studied using pulsed laser ablation and low pressure RF plasma, which usually used for functional thin film deposition. In addition, bulk and powder were used as the targets and compared the effect for the sterilization . Experimental results suggest that bacillus subtilis var. natto was not sterilized in the only vacuum state. However, they can be sterilized using low pressure RF plasma and pulsed laser ablation plasma irradiation. The effect of the sterilization using powder target was higher than that of bulk target, and that of the pulsed laser ablation plasma was higher than RF plasma. Those results suggest that the effect of sterilization was decided by the density of the high-energy metal atoms and ions.
关键词： plasma sterilization,plasma process,pulsed laser ablation
更新于2025-09-11 14:15:04
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Dynamic Backscattering Halo of Pulsed Laser Beams in Thin Cloud Layers
摘要： We consider the e?ect of the dynamic backscattering halo of pencil beams of light in thin layers of scattering media. Numerical modeling, which immediately demonstrates this e?ect, is performed. A simple analytical theory that provides a numerical criterion for the e?ect visual detection, is proposed.
关键词： numerical modeling,pulsed laser beams,thin cloud layers,analytical theory,dynamic backscattering halo
更新于2025-09-11 14:15:04
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Carbon coated TiO2 nanoparticles prepared by pulsed laser ablation in liquid, gaseous and supercritical CO2
摘要： We report on the synthesis of TiO2 nanoparticles using nanosecond pulse laser ablation of titanium in liquid, gaseous and supercritical CO2. The produced particles were observed to be mainly anatase-TiO2 with some rutile-TiO2. In addition, the particles were covered by a carbon layer. Raman and X-ray diffraction data suggested that the rutile content increases with CO2 pressure. The nanoparticle size decreased and size distribution became narrower with the increase in CO2 pressure and temperature, however the variation trend was different for CO2 pressure compared to temperature. Pulsed laser ablation in pressurized CO2 is demonstrated as a single step method for making anatase-TiO2/carbon nanoparticles throughout the pressure and temperature ranges 5–40 MPa and 30–50 °C, respectively.
关键词： core-shell particles,pulsed laser ablation,nanoparticle size control,supercritical fluids
更新于2025-09-11 14:15:04
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Light-Guided Surface Plasmonic Bubble Movement via Contact Line De-Pinning by In-Situ Deposited Plasmonic Nanoparticle Heating
摘要： Precise spatio-temporal control of surface bubble movement can benefit a wide range of applications like high-throughput drug screening, combinatorial material development, microfluidic logic, colloidal and molecular assembly, etc. In this work, we demonstrate that surface bubbles on a solid surface are directed by a laser to move at high speeds (> 1.8 mm/s), and we elucidate the mechanism to be the de-pinning of the three-phase contact line (TPCL) by rapid plasmonic heating of nanoparticles (NPs) deposited in-situ during bubble movement. Based on our observations, we deduce a stick-slip mechanism based on asymmetric fore-aft plasmonic heating: local evaporation at the front TPCL due to plasmonic heating de-pins and extends the front TPCL, followed by the advancement of the trailing TPCL to resume a spherical bubble shape to minimize surface energy. The continuous TPCL drying during bubble movement also enables well-defined contact line deposition of NP clusters along the moving path. Our finding is beneficial to various microfluidics and pattern writing applications.
关键词： pulsed laser,stick-slip motion,nanoparticles,plasmonic heating,micro-bubbles
更新于2025-09-11 14:15:04
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Formation of poly-crystalline BaSi2 thin films by pulsed laser deposition for solar cell applications
摘要： A new growth method for BaSi2 thin films by using pulsed laser deposition (PLD) on transparent SiO2 and CaF2 substrates has been developed. X-ray diffraction and Raman spectroscopy revealed the poly-crystalline property of the deposited films. By introducing a thin Si buffer layer on SiO2 substrate, the crystalline quality of BaSi2 thin films were improved. BaSi2 thin films exhibited a Ba/Si ratio very close to 0.5, indicating the good stoichiometry control of PLD growth. The absorption coefficient of the poly-BaSi2 reached 105 cm-1 and its band gap was deduced to be 1.32 eV, which are similar to those grown by molecular beam epitaxy or sputtering. A maximum photoresponsivity of 12.5 mA/W was achieved in the BaSi2 thin film, which implies the potential of PLD-deposited BaSi2 for thin film solar cell applications.
关键词： Thin films,BaSi2,Solar energy materials,Pulsed laser deposition
更新于2025-09-11 14:15:04
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Producing graphene nanosheets by pulsed laser ablation: Effects of liquid environment
摘要： Effects of liquid environment on the characteristics of graphene nanosheets produced by the laser ablation method have been studied experimentally. The fundamental wavelength of a pulsed Nd:YAG laser at 1064 nm with 7 ns pulse width and 5 Hz repetition rate was employed to irradiate a graphite target in distilled water, liquid nitrogen, alcohol, acetone, and two concentrations of cetyltrimethylammonium bromide. Produced carbon nanostructures were diagnosed using Ultraviolet-Visible-Near Infrared and Fourier transform infrared spectroscopy, x-ray diffraction, Raman spectroscopy, transmission electron microscopy, and field emission scanning electron microscope images. Results show that different carbon nanostructures such as carbon nanoparticles and fluorine, as well as graphene nanosheets were formed in various liquid environments. The size and morphology of nanostructures strongly depends on the liquid environments and, among these liquids, water is the most capable one to produce graphene nanosheets.
关键词： Raman,carbon nanoparticles,graphene nanosheets,graphite,pulsed laser ablation
更新于2025-09-11 14:15:04
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[IEEE 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Honolulu, HI, USA (2018.7.18-2018.7.21)] 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Hybrid multi-wavelength photoacoustic imaging
摘要： Multi-wavelength photoacoustic (PA) imaging has been studied extensively to explore the spectroscopic absorption contrast of biological tissues. To generate strong PA signals, a high-power wavelength-tunable pulsed laser source has to be employed, which is bulky and quite expensive. In this paper, we propose a hybrid multi-wavelength PA imaging (hPAI) method based on combination of single-wavelength pulsed and multi-wavelength continuous-wave (CW) laser sources. By carefully controlling laser illumination sequence (pulse-CW-pulse), and extracting the PA signals’ difference before and after heating of CW lasers, the optical absorption property of multi-wavelength CW lasers could be obtained. Compared with conventional PA imaging, the proposed hPAI shows much lower system cost due to the usage of single-wavelength pulsed laser and cheap CW lasers. Theoretical analysis and analytical model are presented in this paper, followed by proof-of-concept experimental results.
关键词： photoacoustic imaging,continuous-wave laser,multi-wavelength,pulsed laser,hybrid imaging
更新于2025-09-10 09:29:36