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Single photon emission from top-down etched III-nitride quantum dots
摘要： We report the single photon emission properties of III-nitride quantum dots (QDs) fabricated by electrochemical etching method from an epitaxial wafer. Through such top-down fabrication, QDs with diameters of sub-10 nm are obtained, embedded in GaN nanoneedles. Owing to the size induced quantum con?nement effect, the photoluminescence of the QDs exhibits a 3.35 nm blueshift compared with that of the epitaxial wafer. At low temperature, a second order correlation value down to 0.123 is observed, indicating a high-purity single photon emission. Our QDs manifest single photon emission at a temperature up to 130 K with a high degree of polarization of 0.69, comparable to those QDs synthesized by epitaxial growth. Our work demonstrates single photon emission are viable in top-down QDs by electrochemical etching III-nitride wafers.
关键词： single photon emission,III-nitrides,quantum dot,electrochemical etching
更新于2025-09-16 10:30:52
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Superficial photothermal laser ablation (SPLA) of exa??vivo sheep esophagus using a conea??shaped optical fiber tip
摘要： Superficial photothermal laser ablation (SPLA) may be a useful therapeutic approach producing a depth of injury that is sufficient to eliminate mucosal lesion but not deep enough to induce thermal effects in deeper tissue layers. The purpose of this preliminary study is twofold: to describe design steps of a fiber probe capable of delivering a tightly focused laser beam, including Monte-Carlo based simulations, and (2) to complete the initial testing of the probe in a sheep esophagus model, ex vivo. The cone-shaped (tapered) fiber tip was obtained by chemical etching of the optical fiber. A 1505 nm diode laser providing power up to 500 mW was operated in continuous-wave. The successful SPLA of the sheep mucosa layer was demonstrated for various speed-power combinations, including 300 mW laser power at a surface scanning rate of 0.5 mm/s and 450 mW laser power at a surface scanning rate of 2.0 mm/s. Upon further development, this probe may be useful for endoscopic photothermal laser ablation of the mucosa layer using relatively low laser power.
关键词： Photothermal ablation,chemical etching,fiber probe,mucosa,Monte Carlo
更新于2025-09-16 10:30:52
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Effect of acid etching, Er, Cr: YSGG laser conditioning and combining on shear bond strength of orthodontic metal bracket
摘要： Aim The present study aims to evaluate the shear bond strength and the adhesive remnants index (ARI) of metal brackets. For this purpose, enamel etched with acid, Er; Cr: YSGG (2780 nm) laser, and a combination of them. Methods In this study, 60 human premolars were divided into three groups (acid, Er, Cr: YSGG (2780 nm) laser, and combined etching). Each group contains 20 teeth. For testing of shear bond strength (SBS), the force applied by a universal testing machine. All the samples were examined under a light stereomicroscope to determine the bond failure mode. Results The results revealed that the laser-acid group had the maximum mean shear bond strength while the acid group had the minimum shear bond strength. The values of mean shear bond strength obtained of 25.90, 16.94, and16.60 MPa for laser-acid, laser, and acid, respectively. Laser and acid groups were negligibly different from each other, while they were significantly different from the lasers–acid group (p < 0.05). Regardless of the preparation of the enamel, bond failure occurred predominantly in the enamel-adhesive site. Conclusions Er, Cr: YSGG (2780 nm) laser conditioning in combination with acid led to high shear bond strength, but the hazardous effect on tooth should be considered. The bond failure mode was almost similar among all three groups, where there was no adhesive left on the surface of the tooth.
关键词： Er,Shear bond strength,Orthodontic bracket,Cr: YSGG laser,Acid etching
更新于2025-09-12 10:27:22
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Wet chemical etching of cadmium telluride photovoltaics for enhanced open-circuit voltage, fill factor, and power conversion efficiency
摘要： Cadmium telluride (CdTe) is one of the leading photovoltaic technologies with a market share of around 5%. However, there still exist challenges to fabricate a rear contact for ef?cient transport of photogenerated holes. Here, etching effects of various iodine compounds including elemental iodine (I2), ammonium iodide (NH4I), mixture of elemental iodine and NH4I (I?/I3? etching), and formamidinium iodide were investigated. The treated CdTe surfaces were investigated using Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The CdTe devices were completed with or without treatments and tested under simulated AM1.5G solar spectrum to ?nd photoconversion ef?ciency (PCE). Based on Raman spectra, XRD patterns, and surface morphology, it was shown that treatment with iodine compounds produced Te-rich surface on CdTe ?lms, and temperature-dependent current–voltage characteristics showed reduced back barrier heights, which are essential for the formation of ohmic contact and reduce contact resistance. Based on current–voltage characteristics, the treatment enhanced open-circuit voltage (VOC) up to 841 mV, ?ll factor (FF) up to 78.2%, and PCE up to 14.0% compared with standard untreated CdTe devices (VOC ; 814 mV, FF ; 74%, and PCE ; 12.7%) with copper/gold back contact.
关键词： open-circuit voltage,fill factor,Cadmium telluride,wet chemical etching,photovoltaics,power conversion efficiency
更新于2025-09-12 10:27:22
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Assessment of microcracks and shear bond strength after debonding orthodontic ceramic brackets on enamel priorly etched by different Er,Cr:YSGG and Er:YAG laser settings without acid application: An in vitro study
摘要： Background data > Enamel microcrack formation has a high incidence after mechanical debonding of ceramic brackets. This may be due to high delivered shear bond strength values when enamel is priorly etched by phosphoric acid. It is still not well elucidated in the literature if laser etching affects enamel the same way. The aim of the research was to analyze different Er,Cr:YSGG and Er:YAG laser etching settings as an alternative to phosphoric acid, in an attempt to prevent enamel microcrack formation during laser etching and mechanical debonding, while reducing the shear bond strength to the minimal clinical acceptable value. Materials and methods > One hundred and thirty-three teeth were randomly divided into 7 experimental groups according to their etching modalities. Settings used for enamel etching were in Er,Cr:YSGG groups: Er,Cr:YSGG (1.5 Watt, W/20 Hertz, Hz); Er,Cr:YSGG (1.5 W/15 Hz) and Er,Cr:YSGG (2 W/20 Hz) and settings used for enamel etching in Er:YAG groups were: Er:YAG (60 millijoules , mJ), Er:YAG (80 mJ) and Er:YAG (100 mJ). Group C etched with 37% phosphoric acid served as control. Microscopic analysis was performed to assess presence of enamel microcracks. Shear bond strength was evaluated after thermocycling using Weibull survival analysis. Results > All groups showed a reduction in additional microcracks after debonding when compared to control, but only group Er:YAG (60 mJ) exhibited a statistically significant difference. Groups Er:YAG (80 mJ), control and Er:YAG (100 mJ) showed respectively the highest probability of survival at various stress levels followed by groups Er:YAG (60 mJ); Er,Cr:YSGG (1.5 W/15 Hz); Er,Cr:YSGG (2 W/20 Hz) and Er,Cr:YSGG (1.5 W/20 Hz) that presented a relatively considerable risk of failure, even at low stress levels.
关键词： Shear bond strength,Microcracks,Etching,Erbium laser
更新于2025-09-12 10:27:22
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Fast smoothing on diamond surface by inductively coupled plasma reactive ion etching
摘要： The synergetic effects of surface smoothing exhibited during the inductively coupled plasma reactive ion etching (ICP-RIE) of free-standing polycrystalline diamonds (PCDs) were investigated. Changing the assistive gas types generated variable surface oxidation states and chemical environments that resulted in different etching rates and surface morphologies. The main reaction bond mechanism (C–O) during ICP-RIE and the ratio of C–O–C/O–C=O associated with the existence of a uniform smooth surface with root mean square (RMS) roughness of 2.36 nm were observed. An optimal process for PCD smoothing at high etching rate (4.6 lm/min) was achieved as follows: 10% gas additions of CHF3 in O2 plasma at radio frequency power of 400 W. The further etched ultra-smooth surface with RMS roughness <0.5 nm at etching rate of 0.23 lm/min that being produced by transferring this optimum recipe on single crystal diamonds with surface patterns confirmed the effectiveness of the fast smoothing approach and its feasibility for diamond surface patterning.
关键词： surface smoothing,diamond,etching rate,ICP-RIE,surface morphology
更新于2025-09-12 10:27:22
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[IEEE 2019 20th International Conference of Young Specialists on Micro/Nanotechnologies and Electron Devices (EDM) - Erlagol (Altai Republic), Russia (2019.6.29-2019.7.3)] 2019 20th International Conference of Young Specialists on Micro/Nanotechnologies and Electron Devices (EDM) - Development of Technology Formation of the Optical Waveguide Structures Based on InP by Plasma Etching
摘要： The paper presents the process development results of plasma etching of InP-based structures in inductively coupled plasma in the Cl2/Ar gas mixture with the addition of N2 and O2. Etching was performed on silicon nitride mask. Dependences of process parameters influence on the etching rate, profile and surface roughness of formed elements are shown. Elements of optical waveguide structures were fabricated, using developed etching process.
关键词： indium phosphide,plasma etching,Optoelectronics
更新于2025-09-12 10:27:22
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Composition and phases in laser welded Al-Cu joints by synchrotron x-ray microdiffraction
摘要： This paper presents the characterization of the intermetallic phases of laser-welded Al-Cu joints by synchrotron trough-the-substrate microdiffraction combined with SEM/EDX and etched/non-etched optical micrographs. Transmission microdiffraction offers the spatial resolution and beam flux necessary to study the intermetallic phases, which in conjunction with the excellent contrast of etched micrographs, rendered possible the phase identification. It was found that the major phases are Al2Cu (θ), Al4Cu9 (γ1) and AlCu (η2) were formed. The Al3Cu4 (ζ1) and δ phases where formed in less amount and found to be the primary cause for cracks inside the weld seam and therefore for the failure of the joint.
关键词： Cu,identification,transmission microdiffraction,Al,intermetallic,Laser Welding,etching
更新于2025-09-12 10:27:22
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Improvement of fiber optic based localized surface plasmon resonance sensor by optical fiber surface etching and Au capping
摘要： Fiber optic based localized surface plasmon resonance (FO?LSPR) sensor is one of the biosensors that detects specific biomolecules and can detect the onset of disease. In this paper, we propose two methods to improve the signal to noise ratio (SNR) of the sensor, which is one of the main characteristics of the FO?LSPR sensor. The first method is to increase the intensity of the sensor by increasing the size of gold nanoparticle (Au NP) formed on the optical fiber surface by Au capping method. The second method is to form a structure that reduces the reflection by increasing the roughness of the surface by etching the surface of the optical fiber using the Au NP formed on the surface of the optical fiber as a mask. Increasing the roughness of the optical fiber surface can reduce the background signal of the sensor. The two methods mentioned above can increase the SNR of the sensor. When the SNR of the sensor is increased, the efficiency of the sensor is improved.
关键词： Signal?to?noise ratio,Localized surface plasmon resonance,Surface etching,Au capping,Au nanoparticle
更新于2025-09-12 10:27:22
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A facile light‐trapping approach for ultrathin GaAs solar cells using wet chemical etching
摘要： Thinning down the absorber layer of GaAs solar cells can reduce their cost and improve their radiation hardness, which is important for space applications. However, the lighttrapping schemes necessary to achieve high absorptance in these cells can be experimentally challenging or introduce various parasitic losses. In this work, a facile lighttrapping approach based on wet chemical etching is demonstrated. The rear‐side contact layer of ultrathin GaAs solar cells is wet‐chemically textured in between local Ohmic contact points using an NaOH‐based etchant. The resulting contact layer morphology is characterized using atomic force microscopy and scanning electron miscroscopy. High broadband diffuse reflectance and haze factors are measured on bare and Ag‐coated textured contact layers. The textured contact layer is successfully integrated as a diffusive rear mirror in thin‐film solar cells comprising a 300‐nm GaAs absorber and Ag rear contact. Consistent increases in short‐circuit current density (JSC) of approximately 3 mA cm?2 (15%) are achieved in the textured cells, while the open‐circuit voltages and fill factors do not suffer from the textured rear mirror. The best cell achieves a JSC of 24.8 mA cm?2 and a power conversion efficiency of 21.4%. The textured rear mirror enhances outcoupling of luminescence at open circuit, leading to a strong increase in the external luminescent efficiency.
关键词： ultra‐thin GaAs,wet etching,textured III‐V solar cells,light trapping,luminescence outcoupling
更新于2025-09-12 10:27:22