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Controlled Plasma Thinning of Bulk MoS <sub/>2</sub> Flakes for Photodetector Fabrication
摘要： The electronic properties of layered materials are directly determined based on their thicknesses. Remarkable progress has been carried out on synthesis of wafer-scale atomically molybdenum disulfide (MoS2) layers as a two-dimensional material in the past few years in order to transform them into commercial products. Although chemical/mechanical exfoliation techniques are used to obtain a high-quality monolayer of MoS2, the lack of suitable control in the thickness and the lateral size of the flakes restrict their benefits. As a result, a straightforward, effective, and reliable approach is widely demanded to achieve a flake with control in its thickness for optoelectronic applications. In this study, thick MoS2 flakes are obtained by a short-time bath sonication in dimethylformamide solvent, which are thinned with the aid of a sequential plasma etching process using H2, O2, and SF6 plasma. A comprehensive study has been carried out on MoS2 flakes based on scanning electron microscopy, atomic force microscopy, Raman, transmission electron microscopy, and X-ray photoelectron microscopy measurements, which ultimately leads to a two-cycle plasma thinning method. In this approach, H2 is used in the passivation step in the first subcycle, and O2/SF6 plasma acts as an etching step for removing the MoS2 layers in the second subcycle. Finally, we show that this technique can be enthusiastically used to fabricate MoS2-based photodetectors with a considerable photoresponsivity of 1.39 A/W and a response time of 0.45 s under laser excitation of 532 nm.
关键词： photodetector,MoS2,optoelectronic applications,plasma thinning,two-dimensional materials
更新于2025-09-12 10:27:22
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AIP Conference Proceedings [AIP Publishing PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS: ICAM 2019 - Kerala, India (12–14 June 2019)] PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS: ICAM 2019 - Structural and optical studies of bismuth silicate oxyfluoride glasses for LED applications
摘要： The samples SBS20, SBS25 and SBS30 are prepared by traditional melt quenching method. The XRD pattern of prepared samples confirms the glassy nature and a broad peak at 2θ=280. The Raman spectra indicate that addition of SrF2 into the glass matrix leads to loosening of network. It will create more non- bridging oxygen in the samples. The Absorption spectra shows two peaks at 466 nm and 499 nm due to Bi2+ in different environments. The absorption edge shifted to lower wavelength with lower content of Bi2O3 due to the less amount of Bi3+ ion in the glass matrix. Optical band gap increases from 2.84eV to 2.86eV with increasing the SrF2 content leads to loosening of network. Emission spectra consist of three peaks at 435 nm, 510 nm and 630 nm, blue region is arising from Bi3+ and other two are from Bi2+. 20SBS and 25SBS show white light whereas 30SBS shows yellowish green in CIE diagram. The color purity and correlated color temperature are also calculated.
关键词： optical studies,structural studies,LED applications,bismuth silicate oxyfluoride glasses
更新于2025-09-12 10:27:22
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Advances in nanoplasmonic biosensors for clinical applications
摘要： Biomarkers are unquestionable biological indicators for diagnosis and therapeutic interventions providing appropriate classification of a wide range of health disorders and risk factors. Nonetheless, the detection and quantification of biomarkers need to be tested with sufficient reliability by robust analytical methods in order to assure clinical performance in health care settings. Since the analytical performance is determined by the sensitivity and specificity of the method employed, techniques have been intensively refined in order to avoid the misinterpretation of results and undesirable bias. Although biomarkers can be detected with the existing analytical techniques, to reproducibly quantify them in decentralized settings or remote locations with the required accuracy is still a challenge. Currently, only a few point-of-care devices for biomarker evaluation are commercially available. Thus, more focused research efforts are needed to overcome these limitations in order to provide universal patient-centered care platforms. To this end, plasmonic biosensors can be conveniently used as portable diagnostic devices for attaining timely and cost-effective clinical outcomes. The development of enhanced performance based on nanoplasmonics technology opens the way for sensor miniaturization, multiplexing and point of care testing. This review covers recent advances and applications of plasmonic and nanoplasmonic biosensors intended for biomarker diagnosis in clinical practice, including cancer, cardiovascular and neurodegenerative diseases. The review specially focuses on: (i) recent progress in plasmonics development including the design of singular nanostructured surfaces, (ii) novel chemical functionalization strategies for the appropriate incorporation of bioreceptors and (iii) plasmonic applications as real operative devices in the clinical field. Future prospects in the use of nanoplasmonic sensor platforms for personalised quantification and management of biomarkers directly in body fluids will also be discussed.
关键词： clinical applications,SPR,point-of-care testing,nanoplasmonic biosensors,biomarkers,LSPR
更新于2025-09-12 10:27:22
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Experimental and theoretical studies of CuInS2 thin films for photovoltaic applications
摘要： CuInS2 thin films were synthesized by spray pyrolysis. The films were characterized using X-ray diffraction, Raman spectroscopy, and spectrophotometer (UV–Vis). The structural studies reveal that CuInS2 thin films are of chalcopyrite phase. The complex dielectric constants (εr and εi), the refractive index (n), extinction coefficient (k), absorption coefficient (α), gap energy (Eg), and the optical conductivity (σ) were calculated. The obtained results are suitable for photovoltaic applications. To confirm our experimental results, a series of Ab initio calculations was performed. The generalized gradient approximation and the mBJ potential for the exchange–correlation potential have been used to calculate the band structure, density of states, charge density, and optical properties of CuInS2.
关键词： thin films,optical properties,CuInS2,Ab initio calculations,spray pyrolysis,photovoltaic applications
更新于2025-09-12 10:27:22
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Microwave-Assisted and Green Fabrication of Carbon Quantum Dots from Viburnum opulus for Potential Bioimaging Applications
摘要： Early diagnosis is very strategic for today’s diseases such as cancer and infectious diseases. Most of the mortality in these diseases has not been diagnosed early and the mortality rates decrease significantly in early diagnosed cases. Carbon quantum dots (C-dots), which are fluorescent materials used in early diagnosis methods, are both novel and promising materials. The carbon quantum dots have proved their usefulness in bio-applications with this feature. Herein, we reported that a step facile-green microwave-assisted hydrothermal fabrication of C-dots was carried out from Viburnum opulus as a green substrate (Figure 1). The characterization of the fabricated C-dots from Viburnum opulus was accomplished by Fourier transform infrared spectroscopy (FT-IR), UV-vis spectrophotometer, and field-emission scanning electron microscope (FE-SEM). The carbon quantum dots have multifunctional properties that can be found in many areas. For example, they are important materials that can be used in high-performance nanoprobes, bio-imaging applications, molecule labeling applications, labeling and imaging techniques in cancer cells, and as contrast agents.
关键词： carbon quantum dots,bio-applications,green synthesis,Viburnum opulus
更新于2025-09-12 10:27:22
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A Waveguide Switch Based on Contactless Gap Waveguide Technology
摘要： A novel dual-pole dual-throw (DPDT) waveguide switch is proposed for high-power and low-loss applications. The proposed DPDT was designed based on the contactless properties of the gap waveguide technologies in the Ku frequency band. The DPDT was composed of two concentric contactless cylinders. Standard rectangular waveguide ports (WR 75) and waveguide paths are machined in the middle of these cylinders. The rotational movement of the inner cylinder is realized using two bearings in the top and bottom of the DPDT. The proposed structure is fabricated and the measured results are in good agreement with the simulated ones. The measured insertion loss and return loss for the aligned ports are better than 0.1 and 25 dB in the frequency band ranging from 11 to 13.5 GHz, respectively, and the measured isolation between two adjacent ports is better than 60 dB.
关键词： gap waveguide,Dual-pole dual-throw (DPDT),high-power applications,waveguide switch
更新于2025-09-12 10:27:22
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Electrodeposition of crystalline silicon films from silicon dioxide for low-cost photovoltaic applications
摘要： Crystalline-silicon solar cells have dominated the photovoltaics market for the past several decades. One of the long standing challenges is the large contribution of silicon wafer cost to the overall module cost. Here, we demonstrate a simple process for making high-purity solar-grade silicon films directly from silicon dioxide via a one-step electrodeposition process in molten salt for possible photovoltaic applications. High-purity silicon films can be deposited with tunable film thickness and doping type by varying the electrodeposition conditions. These electrodeposited silicon films show about 40 to 50% of photocurrent density of a commercial silicon wafer by photoelectrochemical measurements and the highest power conversion efficiency is 3.1% as a solar cell. Compared to the conventional manufacturing process for solar grade silicon wafer production, this approach greatly reduces the capital cost and energy consumption, providing a promising strategy for low-cost silicon solar cells production.
关键词： crystalline-silicon solar cells,molten salt,silicon dioxide,photovoltaic applications,electrodeposition
更新于2025-09-12 10:27:22
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Plasmonic Nanolenses Produced by Cylindrical Vector Beam Printing for Sensing Applications
摘要： Interaction of complex-shaped light fields with specially designed plasmonic nanostructures gives rise to various intriguing optical phenomena like nanofocusing of surface waves, enhanced nonlinear optical response and appearance of specific low-loss modes, which can not be excited with ordinary Gaussian-shaped beams. Related complex-shaped nanostructures are commonly fabricated using rather expensive and time-consuming electron- and ion-beam lithography techniques limiting real-life applicability of such an approach. In this respect, plasmonic nanostructures designed to benefit from their excitation with complex-shaped light fields, as well as high-performing techniques allowing inexpensive and flexible fabrication of such structures, are of great demand for various applications. Here, we demonstrate a simple direct maskless laser-based approach for fabrication of back-reflector-coupled plasmonic nanorings arrays. The approach is based on delicate ablation of an upper metal film of a metal-insulator-metal (MIM) sandwich with donut-shaped laser pulses followed by argon ion-beam polishing. After being excited with a radially polarized beam, the MIM configuration of the nanorings permitted to realize efficient nanofocusing of constructively interfering plasmonic waves excited in the gap area between the nanoring and back-reflector mirror. For optimized MIM geometry excited by radially polarized CVB, substantial enhancement of the electromagnetic near-fields at the center of the ring within a single focal spot with the size of 0.37λ2 can be achieved, which is confirmed by Finite Difference Time Domain calculations, as well as by detection of 100-fold enhanced photoluminescent signal from adsorbed organic dye molecules. Simple large-scale and cost-efficient fabrication procedure offering also a freedom in the choice of materials to design MIM structures, along with remarkable optical and plasmonic characteristics of the produced structures make them promising for realization of various nanophotonic and biosensing platforms that utilize cylindrical vector beam as a pump source.
关键词： plasmonic nanostructures,cylindrical Vector Beam printing,Sensing Applications,nanofocusing,plasmonic nanolenses
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Determination of the Residual Amplified Spontaneous Emission in Single-Mode Semiconductor Optical Amplifiers
摘要： The Master-Oscillator-Power-Amplifier (MOPA) is a laser light source best suited to provide high power, stable frequency, and narrow linewidth emission. In state-of-the-art MOPA systems, semiconductor optical amplifiers (SOAs) with single-mode lateral waveguides provide a compromise between the demands for high power on one side and excellent beam quality and small astigmatism of the optical mode on the other. The amplified spontaneous emission (ASE) in SOAs remains a limiting factor for the deployment of the MOPA systems in quantum technology applications. The presence of ASE reduces the carrier density and hence the device efficiency, increases the noise in the output signal, and adds incoherent background radiation that is critical, for example, for atom interferometry applications. It is therefore important to understand the dependence of the ASE on the design and operating conditions of an SOA in detail in order to develop SOAs optimized for applications that require spectrally very pure radiation. In this work, the coherent and the residual ASE power of ridge waveguide (RW) SOAs are experimentally determined as a function of the seed power (optical power at the input of the SOA) and the SOA current. The experiment provides essential information about the suppression of the ASE background and the saturation behaviour of the optical amplifier. The measurement setup is depicted in Fig. 1 (a). The seed laser (ECDL, TE-polarized at 871 nm) is operated far above its threshold to avoid amplification of the spontaneous emission of the seed laser by the SOA. An acousto-optic modulator (AOM) is used to set the seed power. The laser beam is then fed into the 6 mm long SOA. A non-polarizing beam splitter (BS) cube divides the output beam into two parts. One part (reference beam) is detected using a power meter (PM). The spectrum of the second part is recorded using an Advantest Q8347 optical spectrum analyser (OSA). The measured data is analysed using the correlation between optical power measured with the power meter and the optical spectrum. The ASE power is reconstructed from the remaining ASE (fitted) spectrum after removing the coherent part. Fig. 1(b) shows the measured total output, ASE and coherent powers retrieved from the spectrum as a function of the seed power. The measured quantities in Fig. 1(b) are compared to theoretical values which are calculated using a SOA model similarly as described in [2]. The carrier-density dependent spectra of the gain and the spontaneous emission are obtained from a microscopic model taking into account the waveguide structure [3]. The comparison shows good qualitative agreement between theory and measurement. We show how the experimental findings are used to validate and calibrate the model and how the model can be applied to compare the performance (coherent power, ASE background, saturation behaviour) of SOAs at different seed powers, injection current setting, different lengths or different lateral geometries.
关键词： ridge waveguide SOAs,semiconductor optical amplifiers,Master-Oscillator-Power-Amplifier,quantum technology applications,amplified spontaneous emission
更新于2025-09-12 10:27:22
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Laser-ion acceleration using mixed compositions: Tailoring the target for each species
摘要： Particle-in-cell simulations of laser-ion acceleration demonstrate marked discrepancies in the acceleration experienced by the different ion species in complex target compositions, especially when the target becomes relativistically transparent to the pulse during irradiation. Beginning with proton contaminants in a carbon target, we show how the higher charge-to-mass ratio of the protons results in species stratification and late-time suppression of the carbon acceleration. The target normal sheath acceleration (TNSA) primarily experienced by the protons can be exploited to mitigate this tamping by using a shaped rear surface of the target, leaving the break-out afterburner-driven carbons to accelerate close to the laser axis and then experience less tamping during a late-time TNSA phase. We then explore preferentially accelerating the lighter species in a mixed composition target, particularly focusing on deuteron beam applications. We examine three different target compositions with the same areal electron density, CD2, CH2, and 7LiD, and propose an alternative shaping of the rear surface of 7LiD to increase the number of high-energy deuterons in the beam.
关键词： target normal sheath acceleration,deuteron beam applications,break-out afterburner,mixed compositions,laser-ion acceleration
更新于2025-09-12 10:27:22