- 标题
- 摘要
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- 实验方案
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Efficient metallic nanowire welding using eddy current method
摘要： In this study, M-NWs such as silver nanowires (AgNWs) and copper nanowires (CuNWs) were welded only at junction resistively by a novel method using indirect Eddy current through the inductive power transfer. By applying the inductive power of 45 kHz alternating current (AC) power indirectly for 6 s to the M-NW network deposited on polymer substrates, the decrease of sheet resistance up to ~67.9 % for AgNW and ~49.9 % for CuNWs could be obtained without changing the optical transmittance. For AgNWs, after the welding the decrease of surface roughness from 44.5 nm to 26.3 nm which is similar to a height of single layer AgNW (22.2 nm) for a bilayer junction could be also observed. For AgNWs coated on transparent flexible substrate, after the cyclic bending of 10,000 times, no change of resistance (ΔR/R0) of the AgNWs after the welding was observed and the welded AgNWs were not easily peeled off from the substrate. It is believed that this novel welding method can be applied not only to all kinds of metal nanowires on various flexible low-temperature polymer substrates but also to large area at a short time and at low-cost.
关键词： nanowelding,inductive coil system,Eddy current,nanowire
更新于2025-09-23 15:21:01
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Nanoscale charge transport and local surface potential distribution to probe defect passivation in Ag doped Cu2ZnSnS4 absorbing layer
摘要： The performance of earth abundant Cu2ZnSnS4 (CZTS) material is limited by high deficit of open circuit voltage (VOC) which is mainly due to the easy formation of CuZn antisite defects. Suppression of CuZn defects is thus inevitably required for further developments in CZTS based solar cells. We studied systematic increase of Ag doping in CZTS thin film and investigated the nanoscale electrical properties using kelvin probe force microscopy (KPFM) and current sensing atomic force microscopy (CAFM) to probe CuZn defects. Crystallographic analysis indicated the successful partial substitution of Cu+ ions by large size Ag+ ions. The considerable decrease in grain boundary potential from 66.50 ± 5.44 mV to 13.50 ± 2.61 mV with Ag doping, suggesting the substantial decrease in CuZn defects. Consequently, CAFM measurement confirms the remarkable increment in minority carrier current with Ag doping and their local mobility in CZTS layer. Finally, the lower persistent photoconductivity (PPC) and fast decay response of photogenerated carriers for Ag doped CZTS photodetector further validate our results. This study provides a fresh approach of controlling deleterious CuZn defects in CZTS by tuning Ag content that may guide researchers to develop next generation high performance CZTS based solar cells.
关键词： nanoscale surface potential and current,CZTS solar cells,Ag doped CZTS,defects,photodetector
更新于2025-09-23 15:21:01
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Discrete-Pulsed Current Time Method to Estimate Channel Thermal Resistance of GaN-Based Power Devices
摘要： A simple electrical method to extract device channel thermal resistance in transistors is presented here. The method compares the dc to discrete-pulsed characteristics and estimates the effective increase in channel temperature under dc biasing conditions. Using the discrete-pulsed I versus t method, the self-heating of the device is effectively eliminated, which helps avoiding the underestimation of the device channel thermal resistance, therefore, making it possible to perform thermal measurements at the high power operation. This technique was applied to lateral GaN HEMTs with three different substrates as well as vertical GaN current aperture vertical electron transistor (CAVET) on sapphire, which proved its sensitivity and validity for different device structures and geometries.
关键词： high-electron mobility transistors (HEMTs),self-heating,current aperture vertical electron transistor (CAVET),Channel thermal resistance
更新于2025-09-23 15:21:01
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Transport in a thin topological insulator with potential and magnetic barriers
摘要： We study transport across either a potential or a magnetic barrier which is placed on the top surface of a three-dimensional thin topological insulator (TI). For such thin TIs, the top and bottom surfaces interact via a coupling λ which influences the transport properties of junctions constructed out of them. We find that for junctions hosting a potential barrier, the differential conductance oscillates with the barrier strength. The period of these oscillations doubles as the coupling λ changes from small values to a value close to the energy of the incident electrons. In contrast, for junctions with a magnetic barrier, the conductance approaches a nonzero constant as the barrier strength is increased. This feature is in contrast to the case of transport across a single TI surface where the conductance approaches zero as the strength of a magnetic barrier is increased. We also study the spin currents for these two kinds of barriers; in both cases, the spin current is found to have opposite signs on the top and bottom surfaces. Thus this system can be used to split applied charge currents to spin currents with opposite spin orientations which can be collected by applying opposite spin-polarized leads to the two surfaces. We show that several of these features of transport across finite width barriers can be understood analytically by studying the δ-function barrier limit. We discuss experiments which may test our theory.
关键词： magnetic barrier,transport,spin current,potential barrier,topological insulator
更新于2025-09-23 15:21:01
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The Influence of the EVA Film Aging on the Degradation Behavior of PV Modules Under High Voltage Bias in Wet Conditions Followed by Electroluminescence
摘要： The influence of the ethylene-vinyl acetate (EVA) film quality on potential induced degradation was studied on in-house developed mini modules with p-type monocrystalline silicon solar cells. The modules were assembled with EVA films of equivalent qualities, but different ages and exposed to an accelerated test (relative humidity = 85%, T = 60 °C, Vbias = +1000 V). The age of the EVA film was determined from the time we received the EVA film, and opened the sealed enclosure and the time of lamination. After the EVA film was removed from the sealed enclosure, it was kept in a dark place at room temperature. The storage times of the “fresh,” “aged,” and “expired” films were: less than 14 d, around 5 mo, and more than 5 years, respectively. While modules with a “fresh” EVA film exhibit almost no degradation, the modules with the “aged” EVA film degrade very rapidly and severely. Their degradation rate was around 0.2%/d during the 2000 h of damp heat test. We also observed a strong silver line corrosion, which occurs because of the peroxide leftovers in the “aged” EVA films.
关键词： photovoltaic (PV) modules,high voltage stress,EVA film,Degradation,potential induced degradation (PID),leakage current
更新于2025-09-23 15:21:01
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A 28-GHz Low-Power Vector-Sum Phase Shifter Using Biphase Modulator and Current Reused Technique
摘要： In this letter, we present a low-power vector-sum phase shifter for upcoming 5G communication at 28 GHz. The ±I/±Q signals for phase synthesis by vector adder (VA) are generated by a 90° coupler and two re?ection-type biphase modulators. Modulators are only biased at 0 and 1.8 V to avoid large insertion loss near their phase reversal region. Our proposed single-ended two branches quadrature structure can avoid the differential variable gain ampli?er and achieve low power and compact area. In addition, we use the current reused technique to connect VA and output buffer to save dc power and suppress a change in output impedance among different phase states. The measured average peak gain is ?3.75 dB at 29.25 GHz. Across all phase states, the measured IP1 dB is better than 5 dBm. The 3-dB bandwidth of S21 is 27–33 GHz. Input and output return losses are also better than 10 dB at this frequency range. Total dc power consumption is only 6.6 mW for 1.8 V supplied voltage. To the best of our best knowledge, this phase shifter has low dc power and compact area at K-band and Ka-band.
关键词： vector adder (VA),phase-invertible variable attenuators (PIVAs),Biphase modulator (BM),current reused technique,vector-sum phase shifter (VSPS),buffer ampli?er (BA)
更新于2025-09-23 15:21:01
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A Comparative Study on Neural Network Based Controllers Used in Grid-Interactive Solar System
摘要： This paper proposes a comparative assessment of NN based current controllers followed by hardware validation towards power quality improvement in grid-interactive VSI controlled solar system. The steady state errors, transient disturbances and high current harmonic effects encountered in conventional linear PI and PR controllers are nullified by employing intelligent adaptive current controller. Three adaptive current control strategies viz. ADALINE-LMS, ALLMS, and VLAS-LMS are identified by using artificial neural network topology having been controlled by different weight-regulating algorithms which helps in minimizing current harmonics generated by the widespread use of VSI, non-linear loads, faults and uncertain polluted grid. A comprehensive comparative study is driven from the proposed adaptive controller’s stability and convergence criterion, current magnitudes calculated at different power zones, % overshoot, settling time and power quality and analyzed under numerous operating conditions. From the comparative assessment performed in between conventional and intelligent current controllers, it is confirmed that the intelligent control technique performs best under the non-linear loads and transient conditions whereas all the controllers perform equally good under the linear loads. Proposed methods are simulated in MATLAB/Simulink and their effectiveness is compared in terms of time responses, stability and low-order current harmonics compensation capability. The robustness of the intelligent current controller is established through the experimental performances using dSPACE RTI 1202.
关键词： grid-interactive solar,power quality,stability,dSPACE,neural network (NN),current controllers (cc),time response
更新于2025-09-23 15:21:01
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Ti/Au/Al/Ni/Au low contact resistance and sharp edge acuity for highly scalable AlGaN/GaN HEMTs
摘要： In this letter, we have reported a novel metal scheme Ti/Au/Al/Ni/Au for ohmic contact on AlGaN/GaN high electron mobility transistors (HEMTs). The reported metal scheme is observed to show minimum metal out-diffusion and sharp edge acuity at high temperature annealing, which facilitates aggressive scaling of source drain separation (LSD). We have demonstrated LSD as low as 300 nm with gate length (Lg) of 100 nm for this metal stack. We observed improvement in ON-Resistance (RON) from 3 ?.mm to 1.25 ?.mm, transconductance (gm) from 276 mS/mm to 365 mS/mm, saturation drain current (IDS,sat) from 906 mA/mm to 1230 mA/mm and unity current gain frequency (fT) from 70 GHz to 93 GHz by scaling LSD from 3 μm to 300 nm. The gate length for all devices were 100 nm.
关键词： Edge acuity,HEMT,smooth surface,current gain cut-off frequency,ohmic contact resistance,GaN
更新于2025-09-23 15:21:01
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Radiation Hardness Comparison of CMOS Image Sensor Technologies at High Total Ionizing Dose Levels
摘要： The impact of the manufacturing process on the radiation induced degradation effects observed in CMOS image sensors at the MGy total ionizing dose levels is investigated. Moreover, the vulnerability of the partially pinned photodiodes at moderate to high total ionizing doses is evaluated for the first time to our knowledge. It is shown that the 3T standard partially pinned photodiode has the lowest dark current before irradiation, but its dark current increases to ~1 pA at 10 kGy(SiO2). Beyond 10 kGy(SiO2), the pixel functionality is lost. The comparison between several CIS technologies points out that the manufacturing process impacts the two main radiation induced degradations: the threshold voltage shift of the readout chain MOSFETs and the dark current increase. For all the tested technologies, 1.8V MOSFETs exhibit the lower threshold voltage shift and the N MOSFETs are the most radiation tolerant. Among all the tested devices, 1.8V sensors achieve the best dark current performance. Several radiation-hard-by-design solutions are evaluated at MGy level to improve further the understanding of CIS radiation hardening at extreme total ionizing dose.
关键词： Gate Overlap,Radiation Effects,Drain,CMOS Image sensors,Partially Pinned Photodiode,Dark Current,TID,Threshold shift,RHBD
更新于2025-09-23 15:21:01
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ISFET Arrays in CMOS: A Head-to-Head Comparison between Voltage and Current Mode
摘要： This paper demonstrates and compares three configurations for ISFET arrays fabricated in unmodified CMOS that facilitate chemical imaging with linear pH-to-output conversion. Specifically, the typical voltage-mode source-follower configuration is compared against our recently proposed current-mode approach using an ISFET in velocity saturation. These two topologies are also compared against an extension of the current-mode topology to include a programmable-gate capacitor inside the pixel stack for offset compensation. Various performance metrics such as linearity, speed, power consumption, size, attenuation and noise have been experimentally measured to quantify the performance of each approach and a figure-of-merit has been defined to capture the overall performance. Using this figure-of-merit the current-mode approach results in the best overall performance. Through this work however, the relative merits and limitations of each approach are identified to be used as a guide for future designs which are usually application-specific. Furthermore, we illustrate methods used to obtain standard ISFET performance metrics in order to standardize the comparison of ISFET arrays using the figure-of-merit.
关键词： CMOS,pH sensor,ISFET,voltage-mode,programmable-gate,array,current-mode
更新于2025-09-23 15:21:01