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European Microscopy Congress 2016: Proceedings || An in-situ Low Energy Argon Ion Source for Local Surface Modification
摘要： A new in-situ low energy ion source for surface modification of a sample surface has been designed. The source is based on the principle of low energy ion bombardment from a beam of ions such as Ar+, N+, or He+ can be used for a local modification of the sample surface. Typical energies are in the range 10 - 100 eV, covering the interaction types from chemical reaction to ion etching and to ion implantation. The source is based on the following principle: electrons from a filament are accelerated towards a grid by a potential difference between the filament and the grid. The electrons enter a gas-filled region between the grid and the sample, where they ionize the gas. The ions are then accelerated towards the sample by a potential difference between the grid and the sample. The source produces a static beam of ions with a selectable energy of 10-100 eV and a full width half maximum (FWHM) of 7.1 um. This corresponds to a central ion current density of 0.019 nA/um2 at 100 eV, which is very similar to the current density at 100 eV of a regular ICP source. In this way, the sample area that is affected by the low energy ions can be more or less defined by the applied bias voltage. The first application can be polishing the top surface of a TMD laminate produced by CVD, or improvement of and LPE surface prepared by ICP. An example of the interaction with the beam is shown in Figure 1, where a native oxide on Si has been removed in 25 seconds, using 100 eV Ar+ ions.
关键词： Ar+,surface modification,low energy ion source,chemical reaction,FWHM,native oxide removal,ion etching,ICP,current density,static beam,N+,ion bombardment,TMD,He+,LPE,ion implantation,in-situ,gas ionization,filament,grid,CVD
更新于2025-09-19 17:15:36
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Broadband terahertz radiation from metal targets irradiated by a short pulse laser
摘要： The generation of low-frequency radiation from sub-picosecond laser pulses incident on metal targets is investigated. The laser field drives time-varying currents in a thin sub-surface layer of the metal, which emits broadband radiation that peaks at terahertz frequencies. We present a one-dimensional electrostatic model for copper appropriate for the interaction of laser pulses at normal incidence combined with a radiation model for an infinitely thin disk. The latter uses as input a single parameter, the temporal dependence of the integrated current density on axis, which is derived from the electrostatic model. The salient characteristics of the emitted radiation, such as power, energy, and spectra, are calculated for laser pulses with various intensities and pulse durations. The radiated energy per unit solid angle peaks at a small angle off the target normal and tapers off at larger angles. Analytical scaling of radiated energy with incident laser energy, in the low frequency limit, is obtained in the form erad ∝ e3/2 laser. For accurate results, it is imperative to use the full expression for the heat capacity of electrons, in both the degenerate and ideal gas limits. Failure to do so may result in inaccuracies for the computed radiated energy, as large as one order of magnitude. A comparison of calculated and measured radiation energy in the 8–12 GHz frequency range indicates a similar trend with laser energy and comparable magnitude (≈1 fJ).
关键词： current density,terahertz radiation,laser-metal interactions,electron heat capacity,broadband radiation
更新于2025-09-19 17:13:59
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Enhancing Small-Molecule Organic Photodetector Performance for Reflectance-Mode Photoplethysmography Sensor Applications
摘要： Organic photodetector performance for enhancing the sensing abilities of an organic photoplethysmography sensor was investigated. Optimized organic photodetector with an anode interlayer and a cathode interlayer showed reverse dark current density of 22 nA cm-2 at ?2 V and the external quantum efficiency of 53.3% at 0 V. This organic photodetector was fabricated monolithically with an organic light emitting diode on a glass substrate to achieve a reflectance-mode photoplethysmography sensor, demonstrating the impact of organic photodetector device performance on the measured photoplethysmography signal for sensing applications. Furthermore, we estimated the optimal sensor design for circular geometry in terms of device area and distance between organic light emitting diode and organic photodetector to maximize the signal-noise ratio and lower the power consumption of organic photoplethysmography sensor devices. For most favorable photoplethysmography sensor design, signal strength of 130 mV with 600 μW power consumption was measured.
关键词： detectivity,Organic photodetector,OLED,Interlayer,dark current density,signal to noise ratio (SNR),PPG Sensor
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE Pulsed Power & Plasma Science (PPPS) - Orlando, FL, USA (2019.6.23-2019.6.29)] 2019 IEEE Pulsed Power & Plasma Science (PPPS) - Auto-collimation and monitoring of laser beam in high power electron-pumped KrF laser facility
摘要： Record low values in this material system of threshold current density, particularly at elevated temperature, are presented for InP quantum dot lasers. Lasers with Ga0 .5 8 In0 .4 2 P in the dot upper con?ning layer have the lowest threshold current densities, 138 A·cm?2 at 300 K, and 235 A·cm?2 at 350 K (77 °C) (2-mm lasers, uncoated facets). Gain-current density data suggests laser performance with an upper con?ning layer of Gax In1 ?xP with x = 0.54, 0.56 or 0.58 would be similar if not for the very low internal optical mode loss, αi of samples with x = 0.56 and 0.58. Gain measurements at ?xed inversion level suggest that increasing x content in Gax In1 ?xP increases gain at ?xed inversion level but samples with x = 0.54 also exhibit reduced recombination current density. The increasing recombination current density at elevated temperature due to thermal carrier spreading is signi?cantly reduced in samples with x = 0.56 and x = 0.58 but measurements at common operating points attribute this largely to the reduced αi for these samples and given the same αI , samples with x = 0.54, 0.56 and 0.58 would all bene?t from reduced effects due to thermal carrier spreading compared to x = 0.52.
关键词： Quantum dot devices,InP self-assembled quantum dots,semiconductor laser,short wavelength lasers,threshold current density,temperature sensitivity
更新于2025-09-19 17:13:59
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High-current density and high-asymmetry MIIM diode based on oxygen-non-stoichiometry controlled homointerface structure for optical rectenna
摘要： optical rectennas are expected to be applied as power sources for energy harvesting because they can convert a wide range of electromagnetic waves, from visible light to infrared. the critical element in these systems is a diode, which can respond to the changes in electrical polarity in the optical frequency. By considering trade-off relationship between current density and asymmetry of IV characteristic, we reveal the efficiency limitations of MIM diodes for the optical rectenna and suggest a novel tunnel diode using a double insulator with an oxygen-non-stoichiometry controlled homointerface structure (Mox/ Mox?y). A double-insulator diode composed of pt/tio2/tio1.4/ti, in which a natural oxide layer of tio1.4 is formed by annealing under atmosphere. The diode has as high-current-density of 4.6 × 106 A/m2, which is 400 times higher than the theoretical one obtained using Pt/TiO2/ti MiM diodes. in addition, a high-asymmetry of 7.3 is realized simultaneously. These are expected to increase the optical rectenna efficiency by more than 1,000 times, compared to the state-of-the art system. Further, by optimizing the thickness of the double insulator layer, it is demonstrated that this diode can attain a current density of 108 A/m2 and asymmetry of 9.0, which are expected to increase the optical rectenna efficiency by 10,000.
关键词： optical rectenna,oxygen-non-stoichiometry controlled homointerface structure,high-asymmetry,high-current density,MIIM diode
更新于2025-09-19 17:13:59
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Record Photocurrent Density over 26a??mAa??cm <sup>a??2</sup> in Planar Perovskite Solar Cells Enabled by Antireflective Cascaded Electron Transport Layer
摘要： Here an antireflective cascaded SnO2/TiO2-Cl electron transport layer (ETL) is devised to enhance the performance of planar perovskite solar cells (PSCs). The primary optical reflection of planar PSCs at the front side can be dramatically reduced by using cascaded ETL. Based on this strategy, we achieved a record-high short-circuit current density of 26.1 mA cm-2 and a high PCE of 22.9% in FAPbI3-based planar PSCs.
关键词： planar perovskite solar cells,cascaded electron transport layers,anti-reflection,bilayer,short-circuit current density
更新于2025-09-19 17:13:59
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[IEEE 2019 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Guangzhou, China (2019.5.19-2019.5.22)] 2019 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - A Circularly Polarized Waveguide Slot Antenna for Random Array Application
摘要： Record low values in this material system of threshold current density, particularly at elevated temperature, are presented for InP quantum dot lasers. Lasers with Ga0.58In0.42P in the dot upper con?ning layer have the lowest threshold current densities, 138 A·cm?2 at 300 K, and 235 A·cm?2 at 350 K (77 °C) (2-mm lasers, uncoated facets). Gain-current density data suggests laser performance with an upper con?ning layer of GaxIn1?xP with x = 0.54, 0.56 or 0.58 would be similar if not for the very low internal optical mode loss, αi of samples with x = 0.56 and 0.58. Gain measurements at ?xed inversion level suggest that increasing x content in GaxIn1?xP increases gain at ?xed inversion level but samples with x = 0.54 also exhibit reduced recombination current density. The increasing recombination current density at elevated temperature due to thermal carrier spreading is signi?cantly reduced in samples with x = 0.56 and x = 0.58 but measurements at common operating points attribute this largely to the reduced αi for these samples and given the same αI, samples with x = 0.54, 0.56 and 0.58 would all bene?t from reduced effects due to thermal carrier spreading compared to x = 0.52.
关键词： Quantum dot devices,InP self-assembled quantum dots,semiconductor laser,short wavelength lasers,threshold current density,temperature sensitivity
更新于2025-09-19 17:13:59
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Light-trapping strategy for PEDOT:PSS/c-Si nanopyramid based hybrid solar cells embedded with metallic nanoparticles
摘要： In this article, we have investigated the combined role of nanopyramid (NP) array and metal nanoparticles (MNPs) in enhancing the light trapping ability and improving the photo-absorption of PEDOT:PSS/c-Si Hybrid Solar Cells (HSCs) using a 3D ?nite-di?erence time-domain (FDTD) method. A parametric optimization of the essential geometrical parameters of NPs and MNP is performed based on short circuit current density (Jsc). The optimization result reveals that maximum Jsc of 35.91 mA/cm2 is achievable with top textured NP (without MNPs) which is 24.38% higher than the planar counterpart. However, the absorption spectrum is broadened with the insertion of Al MNP at rear side of the HSC. This is also accompanied by almost two fold increase in Jsc to 41.71 mA/cm2 which is 44.47% higher the planar HSCs. The photovoltaic parameters such as Jsc, Voc, PCE and Fill Factor (FF) are calculated using the DEVICE software for NP and NP embedded with Al MNPs based c-Si Solar Cells. The physics at the interface of inorganic nanostructure and organic material layer is thoroughly described. In addition to this, we have tried to decode the underlying physics for the enhancement of photon absorption in nanopyramidal structures and MNPs structures through an extensive analysis of the photo- generation rate, electric ?eld intensity, power absorption pro?les, PCE and FF of nanopyramidal, nanopyramidal with MNP and planar HSCs.
关键词： Absorption,Metal nanoparticles,Short circuit current density,Nanopyramid,PEDOT:PSS,FDTD,Hybrid solar cells
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Singapore, Singapore (2019.8.28-2019.8.30)] 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Towards Transparent on-Waveguide Electrical Circuits in SiN-Photonic Platform
摘要： We demonstrate transparent electrical conductors over SiN waveguides using metallic carbon nanotubes (CNTs). For an optimal coverage of 2 % over a SiN micro-ring resonator (MRR), negligible change in transmission is observed till a current density of 35 μA/μm.
关键词： SiN waveguides,micro-ring resonator,current density,metallic carbon nanotubes,transparent electrical conductors
更新于2025-09-16 10:30:52
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Record Low Threshold Current Density in Quantum Dot Microdisk Laser
摘要： We demonstrate a record low threshold current density of 250 A/cm2 in a quantum dot microdisk laser with a 31-μ m diameter operating at room temperature in continuous wave regime without temperature stabilization. This low threshold current density is very close to the transparency current density estimated in broad-area edge-emitting lasers made of the same epitaxial wafer.
关键词： threshold current density,quantum dots,microdisk laser
更新于2025-09-16 10:30:52