Cerium-doped yttrium aluminum garnet (Y3Al5O12:Ce, YAG:Ce) thin films were prepared by reactive co-sputtering from two separate elemental sources (Y3Al5 alloy and pure cerium) using a dual hollow cathode plasma-jet system in an Ar/O-2 atmosphere. This plasma-based approach enabled spatial control of Ce incorporation through the geometric configuration of the sputtering sources and tailored power input. Film composition and structure were analyzed using LIBS, XRD, and optical methods, revealing a gradient in Ce content across the substrate array. Post-deposition annealing at 1000 degrees C was essential for crystallization and luminescence activation, resulting in the formation of single-phase YAG at low Ce concentrations and a gradual transition toward CeO2-rich films at high Ce loading. Photoluminescence and cathodoluminescence studies showed Ce3+ emission at moderate doping levels, while higher Ce content led to phase segregation, Ce4+ formation, and luminescence quenching. These results demonstrate that dual hollow cathode reactive sputtering provides a flexible approach for controlling the Ce distribution and for exploring the structural and optical behavior of YAG:Ce films under extreme Ce loading conditions.

Fabrication of micropatterns on piezoelectric thin films has been widely investigated as an effective approach to release lateral clamping and improve d33-mode piezoelectric performance. Among various micromachining techniques, femtosecond laser processing has emerged as a promising candidate due to its single-step, maskless, non-destructive, and high-throughput characteristics. However, reports on using this method for patterning piezoelectric materials remain insufficiently explored, particularly for the application of d33-mode devices. In this study, line-shaped micropatterns were successfully fabricated in Pb(Zr,Ti)O3 (PZT) thin films using femtosecond laser processing. Post-annealing effectively restored crystallinity degraded during laser processing, enabling the micropatterns to maintain stable dielectric insulation and ferroelectric switching. The fabricated micropatterns exhibit d33 values comparable to bulk PZT, validating the effectiveness of stress release from substrate clamping. These results demonstrate that femtosecond laser processing offers a feasible route for the high-throughput fabrication of high-performance d33-mode piezoelectric MEMS devices.

To enable in situ, machining-compatible surface modification, sub-nanosecond laser irradiation in polyalphaolefin (PAO) oil was used to directly form amorphous Fe–C layers on medium-carbon steel. In this study, the structural and tribological characteristics associated with the resulting low-friction behavior are investigated. Laser irradiation in oil enables simultaneous carbon incorporation and liquid-confined ultra-fast quenching, producing a fully amorphous Fe–C-rich layer ( 150–200 nm). Ball-on-disk tests show sustained low friction (μ ≈ 0.10–0.12) only under sufficiently developed irradiation within an intermediate pulse energy range around 500–650 μJ; lower energies yield fragile/discontinuous layers, whereas excessive energy (1000 μJ) promotes crystallization as the solidification path approaches the TTT nose. AFM lateral-force measurements reveal progressive microscale friction reduction upon repeated sliding, accompanied by indentation evidence of softening limited to the topmost 5 nm. Raman spectroscopy and cross-sectional transmission electron microscopy further demonstrate friction-induced partial structural ordering and carbon enrichment within a thin surface zone ( 5–10 nm), while the underlying layer remains fully amorphous. These results suggest that the observed low-friction behavior is closely associated with a hierarchical structure combining a load-bearing amorphous Fe–C base layer with a dynamically formed, shear-facilitating surface tribo-layer.

This study presents a laser-assisted surface modification method enabling in-situ carburization of medium-carbon steel in hydrocarbon oil. Sub-nanosecond pulses generate transient high-temperature zones, with the oil acting as both carbon source and quencher. XRD shows a weak broad peak at similar to 41.4 degrees assignable to Fe3C/Fe5C2, consistent with TEM observation of a 50-200 nm amorphous carbide layer. The process maintains surface smoothness (Ra < 0.10 m), nearly doubles hardness, and yields extended low-friction lifetimes in oil as well as reduced friction in dry sliding. Raman analysis further indicated that the amorphous Fe-C layer contains minor carbonaceous species which evolve into a carbon-rich tribofilm during sliding, supporting the intrinsic lubricity of the amorphous phase.

This study presents the fabrication of highly photosensitive undoped zinc oxide (ZnO) thin films for vacuum ultraviolet (VUV) radiation detection, covering the wavelength range of 100–200 nm. ZnO films were deposited using hybrid pulsed reactive magnetron sputtering, assisted by ECWR (electron cyclotron wave resonance) plasma. Control of the ECWR power (PECWR), ranging from 0 to 380 W, played a crucial role in enhancing the films’ photoconductive properties. At PECWR = 200 W, the photosensitivity increased by 8 orders of magnitude compared to films deposited without ECWR assistance. This improvement was attributed to a sharp reduction in dark current due to lower defect density. Photoluminescence and cathodoluminescence spectra revealed a significant reduction in defect-related emissions for films deposited at PECWR = 200 W, confirming fewer intrinsic defects. Raman spectroscopy also showed a decrease in defect-related vibrational modes in the same films. Time-Resolved Microwave Conductivity (TRMC) measurements further supported these findings, demonstrating rapid recombination of charge carriers at 200 W, indicative of low trap densities. These results suggest that precise control of ECWR power allows for optimization of the defect concentration and crystallinity in ZnO films, paving the way for the development of high-sensitivity VUV photodetectors.

Abstract High photon energy vacuum ultraviolet radiation (VUV, 100−200 nm wavelength) is challenging to detect. It easily degrades conventional silicon and semiconductor photodetectors. Fluoride photodetectors can be the answer, but the correlation between fabrication parameters and photodetector performance is not known. Here, the effect of annealing is investigated on the characteristics of neodymium trifluoride thin film/quartz substrate interface and NdF3 photoconductivity within the VUV. Thin films are deposited on unheated and heated (600 °C) substrates with post‐deposition annealing. Dark current of films on unheated substrates decreases by as much as 1/10 as resistance increases from 1 −12 TΩ after annealing. Dark current of films on heated substrates increases even after annealing, resulting in similar photo and dark currents of ≈303.7 nA and poor detectors. Fluorine diffuses from the film to the substrate during deposition, exacerbated by substrate heating but not by annealing. Fluorine diffusion degrades crystallinity near the interface, increasing the dark current. Fluorine diffusion is absent when MgF2 is used as the heated substrate. Unannealed NdF3/MgF2 detector on 600 °C‐heated substrate and 600 °C‐annealed NdF3/SiO2 detector on unheated substrate exhibit similar resistances of ≈14 TΩ. Considering the film/substrate interface and annealing is crucial when developing VUV photodetectors.

Ultrafast sub-100 picosecond luminescence is vital in many applications involving ultrafast events and time-of-flight systems. Materials exhibiting fast luminescence, such as barium fluoride (BaF2) and zinc oxide (ZnO), also suffer from an intrinsically slow nanosecond (ns) to microsecond (mu s) luminescence. Here, 2.2 micrometer (mu m)- to 5.7 mu m-thick undoped ZnO films on soda-lime glass (SLG) substrates without a buffer layer by a hybrid pulsed reactive magnetron sputtering operating in the medium-frequency range (MF magnetron) assisted by an electron cyclotron wave resonance (ECWR) plasma is deposited. The undoped ZnO films exhibited superior optical properties characterized by intense ultraviolet (UV) luminescence, unprecedented ultrafast decay times, and for the case of MF+ECWR-deposited films, suppressed defect-related visible luminescence. The 2.2 mu m-thick MF-deposited film exhibited the fastest 9-ps decay time at room temperature. The impressive properties of the films are attributed to the use of advanced deposition technology with properly tuned plasma parameters, especially a high degree of dissociation of molecular oxygen together with an increased proportion of activated zinc particles, leading to a higher deposition rate, better crystallinity, fewer defects, and a lower proportion of oxygen vacancies. These films will pave the way toward the development of time-of-flight detectors, high-resolution nuclear imaging cameras, and high-rate ultrafast timing devices. Undoped micrometer (mu m)-thick zinc oxide (ZnO) films with intense ultraviolet (UV) luminescence, ultrafast picosecond decay times, and suppressed defect-related visible luminescence owing to better crystallinity, fewer defects, and decreased oxygen vacancies are deposited on bufferless soda lime glass substrates using a hybrid plasma deposition technique combining pulsed reactive magnetron sputtering operating in the medium-frequency range (MF magnetron) with an electron cyclotron wave resonance (ECWR) plasma. image

Molybdenum carbides (MoC and Mo2C) are being reported for various applications, for example, catalysts for sustainable energies, nonlinear materials for laser applications, protective coatings for improving tribological performance, and so on. A one-step method for simultaneously fabricating molybdenum monocarbide (MoC) nanoparticles (NPs) and MoC surfaces with a laser-induced periodic surface structure (LIPSS) was developed by using pulsed laser ablation of a molybdenum (Mo) substrate in hexane. Spherical NPs with an average diameter of 61 nm were observed by scanning electron microscopy. The X-ray diffraction pattern and electron diffraction (ED) pattern results indicate that a face-centered cubic MoC was successfully synthesized for the NPs and on the laser-irradiated area. Notably, the ED pattern suggests that the observed NPs are nanosized single crystals, and a carbon shell was observed on the surface of MoC NPs. The X-ray diffraction pattern of both MoC NPs and LIPSS surface indicates the formation of FCC MoC, agreeing with the results of ED. The results of X-ray photoelectron spectroscopy also showed the bonding energy attributed to Mo-C, and the sp(2)-sp(3) transition was confirmed on the LIPSS surface. The results of Raman spectroscopy have also supported the formation of MoC and amorphous carbon structures. This simple synthesis method for MoC may provide new possibilities for preparing MoxC-based devices and nanomaterials, which may contribute to the development of catalytic, photonic, and tribological fields.

In this study, we developed a one-step method for fabricating hydrophobic surfaces on copper (Cu) substrates. Cuprous oxide (Cu2O) with low free energy was successfully formed after low-fluence laser direct irradiation. The formation of Cu2O enhanced the hydrophobicity of the Cu substrate surface, and the contact angle linearly increased with the proportion of Cu2O. The Cu2O fabricated by low-fluence laser treatment showed the same crystal plane orientation as the pristine Cu substrate, implying an epitaxial growth of Cu2O on a Cu substrate.

Titanium alloy is widely used in different industrial applications. For the surface modification to improve the tribological properties, laser irradiation is a promising technology, which offers high efficiency, and high automation potential and geometrical flexibility. In this study, a novel method of surface modification for titanium alloys by carbonization using low fluence of laser irradiation in the atmosphere of PAO oil is proposed. Results show that the carbon content on the surfaces significantly increases with the laser shot number, with the laser irradiated spot showing little change of Ra. XPS analysis confirms that the carbon from the oil has bonded to the Titanium inside the alloy. By comparison with that irradiated without oil, the hardness of that irradiated in oil is much higher, demonstrating the feasibility of the surface modification of titanium carbide layer generation. To investigate the tribological properties, laser scanning irradiation in oil with different laser pulses were carried out to create laser modified areas and reciprocating ball-on-disk friction tests under oil lubrication were conducted. The laser modified areas show friction of 0.13, much lower than that of the unirradiated which is approximate 0.55, and the sliding lifetime of low friction is also increased with the laser pulse number. Moreover, by introducing patterning laser irradiation onto the uniformly irradiated area, the wear resistance can be further greatly improved, and the sliding lifetime can extend to 13 times of the optimal result of uniform irradiation.

A calcium fluoride (CaF2) single crystal with asymmetric gold (Au) and aluminum (Al) electrodes is investigated as a photovoltaic sensor of high-energy vacuum ultraviolet (VUV) radiation. A photocurrent of at least 0.13 nA is obtained at zero bias voltage, indicating that the sensor may be self-powered and can be operated without an external voltage source. The sensor is responsive only to wavelengths shorter than 130 nm, corresponding to photon energies greater than 9.5 eV. The 130-nm cutoff wavelength aligns with the transmission edge of the crystal, allowing it to screen out unwanted background UV and visible light without having to use filters. The 5.36 μs (fall time) time response of the sensor is similar to that of a commercial diamond UV sensor (5.05 μs). When operated in reverse- and forward-bias with an applied bias voltage ranging from –9 V to 9 V, the sensor exhibits rectification. In reverse-bias operation, increasing then decreasing the bias voltage leads to hysteresis which is attributed to surface defects at the CaF2/Au interface. As a self-powered filterless VUV sensor with a sufficiently fast response speed, the CaF2 sensor would be attractive for applications requiring high-power VUV light sources to be monitored.

Resonances with both high-quality factor and polarization-independent characteristics are highly desirable for terahertz (THz) sensing. Here, THz sensors based on asymmetric metallic hole arrays (AMHAs) are experimentally demonstrated. Such sensors consisting of four-hole arrays support polarization-independent quasi-bound states in the continuum (BICs). The induced quasi-BIC presents a quality factor exceeding 2000, which enables enhanced sensing for thin membranes. Results show that the frequency shift is 97.5 GHz for the 25-µm thick polyimide (PI), corresponding to a sensitivity of 147.7 GHz/RIU. The sensing performance strongly relates to the enhanced field originating from sharp quasi-BICs. A maximum field enhancement of 15.88 in contrast to the incident field is achieved. When the PI thickness is large than the decay length of enhanced fields, the interaction strength of field-PI becomes weak, resulting in a saturation effect for the shift of quasi-BICs. The proposed sensor possessing polarization-independent quasi-BICs has great potential for practical sensing applications in real-time chemical and biomolecular.

We report on titanium dioxide (TiO2) thin film deposited on a quartz (SiO2) substrate as an improved photoconductive detector for radiation below 200 nm wavelength (vacuum ultraviolet region, VUV). The crystalline film has an anatase phase and an average crystallite size of 10.6 nm. It has a transmission edge at 322 nm and an optical band gap of 3.18 +/- 0.02 eV. Under VUV illumination, the TiO(2 )photoconductive detector exhibited a photocurrent of 5.3 mA at an applied bias voltage of 100 V. The dark current measured without VUV illumination and at the same bias voltage is 8.8 x 10(6) mA, which is 6 orders of magnitude smaller compared to the photocurrent. The photoconductive VUV detector based on TiO2 thin film provides a means of directly measuring VUV radiation compared to detection via the photoluminescence of a scintillator. Copyright (C) 2022 Elsevier Ltd. All rights reserved.

In this study, a terahertz (THz) composite slab (TCS) based on metal grating and dielectric films is experimentally and numerically investigated in the THz region. By combining a dielectric film, the TCS exhibits different sharp resonances for varied polarization waves. A sharp Fano resonance is excited for transverse magnetic (TM) waves, which originates from the introduced asymmetric factor by dielectric films. The film thickness and refractive index can be used for the Fano resonance tuning. The resonant Q -factor can be improved using thinner and lower refractive index films. For transverse electric (TE) modes, a resonance termed guided modes can also be induced when the dielectric film is thick enough. The effects of film thickness and refractive index on these resonances are analyzed in detail. These results demonstrated that this TCS with high Q -factors or narrow resonances for both TM and TE waves is a promising component for THz filter and sensor applications.

Cleavage along the crystalline and cleavage-melt shift were observed on the surface of a ZnO substrate when it was irradiated by single and multiple femtosecond laser pulses, respectively.

With the pursuit of high-precision and high-efficiency machining, laser-assisted machining technology has attracted more and more attention. Especially, ultra-short pulse laser irradiation can facilitate a quite high cooling rate and produce a local active space, which can make the surface modification realized without any removal. In this study, a novel tribo-characteristic improvement technology using ultra-short pulse laser irradiation in oil, with the hydrocarbon composition in oil as a carbon source, was proposed, to realize the surface modification of the workpiece in the same process with machining. Herein, a Ti-6Al-4V disk was irradiated using a pico-second laser in PAO oil under 4 different conditions with changed effective irradiated laser pulses and scanning modes. Besides the uniform laser irradiation, patterning irradiation was also conducted. From the results of the reciprocating friction tests, compared to those uniformed irradiated specimens, patterning irradiation processed surfaces show obviously more stable friction than the as-received metal surface. More importantly, much longer lifetime has been obtained, indicating the enhanced wear resistance. According to the investigation of hardness distribution, laser-induced thermal strain in the patterning irradiation method is considered to be an important factor of wear resistance improvement.

Vacuum ultraviolet radiation (VUV, from 100 nm to 200 nm wavelength) is indispensable in many applications, but its detection is still challenging. We report the development of a VUV photoconductive detector, based on titanium dioxide (TiO2) nanoparticle thin films. The effect of crystallinity, optical quality, and crystallite size due to film thickness (80 nm, 500 nm, 1000 nm) and type of substrate (silicon Si, quartz SiO2, soda lime glass SLG) was investigated to explore ways of enhancing the photoconductivity of the detector. The TiO2 film deposited on SiO2 substrate with a film thickness of 80 nm exhibited the best photoconductivity, with a photocurrent of 5.35 milli-Amperes and a photosensitivity of 99.99% for a bias voltage of 70 V. The wavelength response of the detector can be adjusted by changing the thickness of the film as the cut-off shifts to a longer wavelength, as the film becomes thicker. The response time of the TiO2 detector is about 5.8 μs and is comparable to the 5.4 μs response time of a diamond UV sensor. The development of the TiO2 nanoparticle thin film detector is expected to contribute to the enhancement of the use of VUV radiation in an increasing number of important technological and scientific applications.

A hybrid antireflective structure was fabricated by attaching a polymer-based two-layer coating onto a silicon moth-eye structure, whose power reflectance can remain below 6% in a broad range from 0.6 to 2.5 THz.