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Effect of substrate temperature on bismuth oxide thin films grown by pulsed laser deposition
摘要： We present and discuss on bismuth oxide films grown on cost-efficient BK7 glass slides by pulsed laser deposition using a metallic target. Our choice is of particular interest due to the high number of intermediate bismuth oxides that can form during the oxidation process, along with the polymorphs of the stoichiometric oxide, i.e. bismuth trioxide (Bi2O3). We show that the oxidation degree of bismuth increases with substrate temperature, tS (300-600 °C), when grown in 100 sccm flow at 6 × 10?1 mbar O2 partial pressure. Thin film crystallinity is also increased with tS, as expected. Instead, the refractive index (n) of the films decreases in the visible range, as tS is increased. Furthermore, the transmittance of the films increases with tS to over 60%, especially in the red and near-infrared region (above 600 nm). As a final point, the results are discussed and compared to literature.
关键词： Wemple-DiDomenico model,Optical properties,Thin films,Laser processing,Substrate temperature
更新于2025-09-23 15:21:01
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Micro and Nanoscale Laser Processing of Hard Brittle Materials || Surface nanostructuring of hard brittle materials
摘要： In the recent developments of laser processing technology, there has been exponentially growing interest in surface structuring. A wide variety of shapes and sizes can be achieved for the structures depending on the laser parameters applied. In this chapter, we will be focusing on nanoscale surface structuring. Laser surface nanostructuring is such an attractive process, from a technological point of view, as it is so simple. Nanostructures can be generated on a large surface area using a single-step process; this is impossible on hard brittle materials by any other methods. However, as is the case with many simple technologies, the fundamental science behind it is highly complex. Surface structure generation is attributed to a complex combination of inter- and intrapulse physical processes. This chapter will attempt to clarify the scientific processes of the nanostructure formation mechanism, to describe recent trends in nanostructuring technology, and to present innovative applications of nanostructured surfaces with particular focus on the surface nanostructuring of silicon and zirconia.
关键词： zirconia,surface nanostructuring,LIPSS,silicon,laser processing
更新于2025-09-23 15:21:01
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Chemical effects during the formation of various types of femtosecond laser-generated surface structures on titanium alloy
摘要： In this contribution, chemical, structural, and mechanical alterations in various types of femtosecond laser-generated surface structures, i.e., laser-induced periodic surface structures (LIPSS, ripples), Grooves, and Spikes on titanium alloy, are characterized by various surface analytical techniques, including X-ray diffraction and glow-discharge optical emission spectroscopy. The formation of oxide layers of the different laser-based structures inherently influences the friction and wear performance as demonstrated in oil-lubricated reciprocating sliding tribological tests (RSTTs) along with subsequent elemental mapping by energy-dispersive X-ray analysis. It is revealed that the fs-laser scan processing (790 nm, 30 fs, 1 kHz) of near-wavelength-sized LIPSS leads to the formation of a graded oxide layer extending a few hundreds of nanometers into depth, consisting mainly of amorphous oxides. Other superficial fs-laser-generated structures such as periodic Grooves and irregular Spikes produced at higher fluences and effective number of pulses per unit area present even thicker graded oxide layers that are also suitable for friction reduction and wear resistance. Ultimately, these femtosecond laser-induced nanostructured surface layers efficiently prevent a direct metal-to-metal contact in the RSTT and may act as an anchor layer for specific wear-reducing additives contained in the used engine oil.
关键词： Tribology,Femtosecond laser processing,GD-OES,Surface chemistry,XRD,LIPSS,Laser-induced periodic surface structures,Laser-induced oxide layer
更新于2025-09-23 15:19:57
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Nanodot array deposition via single shot laser interference pattern using laser-induced forward transfer
摘要： Laser-induced forward transfer (LIFT) is a direct-writing technique capable of depositing a single dot smaller than the laser wavelength at small shot energy through the laser-induced dot transfer (LIDT) technique. To deposit a single nanodot in a single shot of laser irradiation, a liquid nanodrop is transferred from donor to receiver and finally solidified via a solid-liquid-solid (SLS) process. In conventional LIDT experiments, multi-shots with step scanning have been used to form array structures. However, interference laser processing can achieve an arrayed process and generate a periodic structure in a single shot. In this study, a femtosecond laser interference pattern was first applied to LIDT, and an array of nanodots was successfully deposited in a single shot, producing the following unit structures: a single dot, adjoining dots, and stacking dots. The diameter of the smallest nanodot was 355 nm, and the narrowest gap between two adjoining nanodots was 17.2 nm. The LIDT technique produces high-purity, catalyst-free that do not require post-cleaning or alignment processes. Given these significant advantages, LIDT can expand the usability of nanodots in a wide range of fields.
关键词： array,laser-induced dot transfer (LIDT),interference laser processing,nanodot,femtosecond laser,Au,solid-liquid-solid (SLS) mechanism
更新于2025-09-23 15:19:57
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Sequences of Sub-Microsecond Laser Pulses for Material Processing: Modeling of Coupled Gas Dynamics and Heat Transfer
摘要： Multipulse laser processing of materials is promising because of the additional possibilities to control the thickness of the treated and the heat-affected zones and the energy efficiency. To study the physics of mutual interaction of pulses at high repetition rate, a model is proposed where heat transfer in the target and gas-dynamics of vapor and ambient gas are coupled by the gas-dynamic boundary conditions of evaporation/condensation. Numerical calculations are accomplished for a substrate of an austenitic steel subjected to a 300 ns single pulse of CO2 laser and a sequence of the similar pulses with lower intensity and 10 μs inter-pulse separation assuring approximately the same thermal impact on the target. It is revealed that the pulses of the sequence interact due to heat accumulation in the target but they cannot interact through the gas phase. Evaporation is considerably more intensive at the single-pulse processing. The vapor is slightly ionized and absorbs the infrared laser radiation by inverse bremsstrahlung. The estimated absorption coefficient and the optical thickness of the vapor domain are considerably greater for the single-pulse regime. The absorption initiates optical breakdown and the ignition of plasma shielding the target from laser radiation. The multipulse laser processing can be applied to avoid plasma ignition.
关键词： laser evaporation,multipulse laser processing,laser plasma,heat transfer,gas dynamics
更新于2025-09-23 15:19:57
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As-fabricated surface morphologies of Ti-6Al-4V samples fabricated by different laser processing parameters in selective laser melting
摘要： The surface morphology of a product plays a crucial role under mechanical loading and chemical environment. Surfaces of Selective Laser Melting (SLM) products often contain high roughness, which varies in different planes as well. The authors have explored the surface characteristics of the SLM samples that are influenced by different combinations of laser processing parameters. The considered processing parameters were Energy Density (ED) and its technological parameters namely laser power, scanning speed and hatch spacing. Additionally, a comparison study has been executed by rescanning effects considering melting with low ED and, thereafter, re-scanning by the best possible laser processing parameters. The results evidently showed that the surface morphologies differ significantly due to different laser processing parameters. Eventually, the thermal and physical behavior of materials, such as the viscosity of the melt pool, thermal and physical stability of the melt pool, solidification time, cooling time, shrinkage, capillary effect, surface tension, balling effect, and the amount of melting of a powder particle, influenced the surface properties of the samples, along with unpredictability. The results showed an interesting correlation between the processing parameters and the occurrence of microcracks on the vertical walls of the specimens caused by the partially melted adhered powder particles.
关键词： Ti-6Al-4V alloy,Selective laser melting,Laser processing parameters,Surface morphology,Rescanning
更新于2025-09-23 15:19:57
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Light Emission from Selfa??Assembled and Lasera??Crystallized Chalcogenide Metasurface
摘要： Subwavelength periodic confinement can collectively and selectively enhance local light intensity and enable control over the photoinduced phase transformations at the nanometer scale. Standard nanofabrication process can result in geometrical and compositional inhomogeneities in optical phase change materials, especially chalcogenides, as those materials exhibit poor chemical and thermal stability. Here the self-assembled planar chalcogenide nanostructured array is demonstrated with resonance-enhanced light emission to create an all-dielectric optical metasurface, by taking advantage of the fluid properties associated with solution-processed films. A patterned silicon membrane serves as a template for shaping the chalcogenide metasurface structure. Solution-processed arsenic sulfide metasurface structures are self-assembled in the suspended 250 nm silicon membrane templates. The periodic nanostructure dramatically manifests the local light–matter interaction such as absorption of incident photons, Raman emission, and photoluminescence. Also, the thermal distribution is modified by the boundaries and thus the photothermal crystallization process, leading to the formation of anisotropic nanoemitters within the field enhancement area. This hybrid structure shows wavelength-selective anisotropic photoluminescence, which is a characteristic behavior of the collective response of the resonant-guided modes in a periodic nanostructure. The resonance-enhanced Purcell effect can manifest the quantum efficiency of localized light emission.
关键词： optical antennas,laser processing,optical nanostructures,metasurfaces,Raman emission
更新于2025-09-23 15:19:57
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Laser Induced Nano and Micro Structures of Molybdenum Surface Applied in Multistage Depressed Collector for Secondary Electron Suppression
摘要： The laser processing molybdenum metal surface method was first proposed to enhance the efficiency of multistage depressed collectors (MDCs). In this study, the secondary electron yield (SEY), surface geometrical morphologies and chemical states of laser processed Mo metal samples were characterized. For the first time, the effects of laser parameters and incident angle of primary electrons on the SEY property of laser induced nano and micro structures of molybdenum surface were investigated. The influence rule of laser processing patterns, power, pitch spacing, scanning speed on surface morphologies and SEY were systematically explored. A maximum SEY of laser processed Mo metal less than one was achieved. The Mo 3d and O 1s core level spectra of Mo metal before and after laser processing were analyzed in this study. Furthermore, the corresponding oxidation states of Mo as well as the relative distribution were elucidated.
关键词： secondary electron yield,laser processing,Mo metal
更新于2025-09-23 15:19:57
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Gate Tunable Symmetric Bipolar Junction Transistor Fabricated via Femtosecond Laser Processing
摘要： Two-dimensional (2D) bipolar junction transistor (BJT) with van der Waals heterostructures plays an important role in the development of future nanoelectronics. Herein, a convenient method is introduced for fabricating a symmetric bipolar junction transistor (SBJT) constructed with black phosphorus and MoS2 with femtosecond laser processing. This SBJT exhibits good bidirectional current amplification thanks to its symmetric structure. Next, we place a top gate on one side of the SBJT to change the difference in the major carrier concentration between the emitter and collector in order to further investigate the effect of electrostatic doping on the device’s performance. The SBJT can also act as a gate tunable phototransistor with good photodetectivity and photocurrent gain of β ~ 21. Scanning photocurrent images are used to determine the mechanism governing photocurrent amplification in the phototransistor. These results promote the development of the applications of multifunctional nanoelectronics based on 2D materials.
关键词： Femtosecond laser processing,Phototransistor,Two-dimensional materials,Bipolar junction transistor,Gate tunable
更新于2025-09-23 15:19:57
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Non-isothermal <i>?2</i> grain growth behaviour of pure titanium under laser quenching
摘要： The primary understanding of laser-induced non-isothermal prior β grain growth behaviour of titanium alloys is given by adopting laser quenching on pure titanium. Results indicate that the prior β grains grow obviously within the limited laser interaction time. By establishing a finite element model combined with numerical approximations, the growth activation energy of prior β grain under laser-induced non-isothermal condition is determined as 44.4 kJ/mol, which is comparable to that under isothermal conditions. Grain boundary migration behaviour of pure titanium under laser-induced non-isothermal conditions is the same as that under isothermal conditions, but the prior β grain growth kinetics is largely accelerated due to the high heat input from the laser beam.
关键词： non-isothermal,Laser processing,pure titanium,crystal growth
更新于2025-09-23 15:19:57