共查询到20条相似文献,搜索用时 375 毫秒
1.
Shi Wun Tong Yu Wang Yi Zheng Man‐Fai Ng Kian Ping Loh 《Advanced functional materials》2011,21(23):4430-4435
One strategy to harvest wide spectral solar energy is to stack different bandgap materials together in a tandem solar cell. Here, it is demonstrated that CVD grown graphene film can be employed as intermediate layer (IML) in tandem solar cells. Using MoO3‐modified graphene IML, a high open circuit voltage (Voc) of 1 V and a high short‐circuit current density (Jsc) of 11.6 mA cm‐2 could be obtained in series and parallel connection, respectively, in contrast to a Voc of 0.58 V and Jsc of 7.6 mA cm‐2 in single PV cell. The value of Voc (Jsc) in the tandem cell is very close to the sum of Voc (Jsc) attained from two single subcells in series (parallel), which confirms good ohmic contact at the photoactive layer/MoO3‐modified graphene interface. Work function engineering of the graphene IML with metal oxide is essential to ensure good charge collection from both subcells. 相似文献
2.
Effects of Trace Amounts of Rare Earth Additions on Microstructure and Properties of Sn-Bi-Based Solder Alloy 总被引:3,自引:0,他引:3
Wenxing Dong Yaowu Shi Zhidong Xia Yongping Lei Fu Guo 《Journal of Electronic Materials》2008,37(7):982-991
The effect of trace amounts of rare earth additions on the microstructure and properties were studied for the Sn-58Bi and
Sn-58Bi-Ag solder alloys. At the same time, the intermetallic compounds (IMCs) in the solder alloys and intermetallic layer
(IML) thickness at the solder/Cu substrate interface were investigated, both as-reflowed and after high-temperature aging.
The results indicate that adding trace amounts of rare earth (RE) elements has little influence on the melting temperature
and microhardness of the solders investigated, but adding RE elements improves the wettability and shear strength of the Sn-58Bi
and Sn-58Bi-Ag solder alloys. In addition, it was found that the addition of RE elements not only refines the microstructure
and size of the IMC particles, but also decreases the IML thickness and shear strength of the Sn-58Bi solder joint after high-temperature
aging. Adding trace amounts of RE elements is superior to adding trace amounts of Ag for improving the properties of the Sn-58Bi
solder. The reason may be related to the modification of the microstructure of the solder alloys due to the addition of trace
amounts of RE elements. 相似文献
3.
Microstructure, solderability, and growth of intermetallic compounds of Sn-Ag-Cu-RE lead-free solder alloys 总被引:4,自引:0,他引:4
C. M. T. Law C. M. L. Wu D. Q. Yu L. Wang J. K. L. Lai 《Journal of Electronic Materials》2006,35(1):89-93
The near-eutectic Sn-3.5 wt.% Ag-0.7 wt.% Cu (Sn-3.5Ag-0.7Cu) alloy was doped with rare earth (RE) elements of primarily Ce
and La of 0.05–0.25 wt.% to form Sn-3.5Ag-0.7Cu-xRE solder alloys. The aim of this research was to investigate the effect
of the addition of RE elements on the microstructure and solderability of this alloy. Sn-3.5Ag-0.7Cu-xRE solders were soldered
on copper coupons. The thickness of the intermetallic layer (IML) formed between the solder and Cu substrate just after soldering,
as well as after thermal aging at 170°C up to 1000 h, was investigated. It was found that, due to the addition of the RE elements,
the size of the Sn grains was reduced. In particular, the addition of 0.1wt.%RE to the Sn-3.5Ag-0.7Cu solder improved the
wetting behavior. Besides, the IML growth during thermal aging was inhibited. 相似文献
4.
提出一种新型的基于超表面的低剖面宽带高增益透镜天线,该透镜采用宽带的电偶极子天线作为馈源,设计中心频率工作在10 GHz.针对超表面透镜在不同位置的折射率的需求,同时提出了一种新型的非谐振超材料单元,该单元由三层介质板组成,中间一层是印有十字形带状线的双层印刷板.通过改变上下两层介质的介电常数,可以达到不同的折射率变化范围,从而实现透镜的中间层和阻抗匹配层对折射率的需求.所提出的透镜天线设计方法可以获得21 dBi的最高增益以及58%的-10 dB阻抗带宽.更重要的是所提出的具有高折射率的超材料单元可以实现只有0.32λ0的透镜厚度,大大减小了透镜的剖面.最后进行了加工实验,对所提出的方法和仿真结果进行了验证,实验结果表明,透镜天线的实测带宽、方向图和增益都与仿真理论结果有较好的吻合度. 相似文献
5.
6.
Man-Lyun Ha Young-Se Kwon 《Microwave and Wireless Components Letters, IEEE》2005,15(6):410-412
We have developed the inverted microstrip line photonic bandgap (IML-PBG) structure using the surface micro-machining technology on the high resistivity silicon (HRS) substrate. Because, when the IML was fabricated, the holes for removing a sacrificial layer were necessary, we have introduced these holes into the PBG structure for the Ku-band stop filter (BSF). Rectangular spiral PBG structure showed the notch characteristics and the array with suitable distance showed the stop band with under -20 dB from 15 to 19 GHz and under -3 dB pass-band loss. 相似文献
7.
In the current research, trace rare earth (RE) element Y was incorporated into a promising lead-free solder, Sn3.8Ag0.7Cu,
in an effort to improve the comprehensive properties of Sn3.8Ag0.7Cu solder. The range of Y content in Sn3.8Ag0.7Cu solder
alloys varied from 0 wt.% to 1.0 wt.%. As an illustration of the advantage of Y doping, the melting temperature, wettability,
mechanical properties, and microstructures of Sn3.8Ag0.7CuY solder were studied. Trace Y additions had little influence on
the melting behavior, but the solder showed better wettability and mechanical properties, as well as finer microstructures,
than found in Y-free Sn3.8Ag0.7Cu solder. The Sn3.8Ag0.7Cu0.15Y solder alloy exhibited the best comprehensive properties compared
to other solders with different Y content. Furthermore, interfacial and microstructural studies were conducted on Sn3.8Ag0.7Cu0.15Y
solder alloys, and notable changes in microstructure were found compared to the Y-free alloy. The thickness of an intermetallic
compound layer (IML) was decreased during soldering, and the growth of the IML was suppressed during aging. At the same time,
the growth of intermetallic compounds (IMCs) inside the solder was reduced. In particular, some bigger IMC plates were replaced
by fine, granular IMCs. 相似文献
8.
9.
A master oscillator power amplifier (MOPA) laser transmitter system at 1047 nm wavelength using a semiconductor laser diode and a diode pumped solid state (Nd:YLF) laser (DPSSL) amplifier is described. A small signal gain of 23 dB, a near diffraction limited beam, l Gbit/s modulation rates and >0.6 W average power are achieved. This MOPA laser has the advantage of amplifying the modulation signal from the laser diode master oscillator (MO) with no signal degradation.<> 相似文献
10.
An XeF (C →A ) laser, pumped at a rate of 290 kW/cm3 with a 600-ns electron-beam pulse, has been operated as an injection-controlled oscillator. A stable cavity has been injected with radiation from a pulsed dye laser source. A significant reduction in laser turn-on time has been achieved, and the laser pulse duration has been extended to 500 ns (FWHM). As a consequence, the laser intrinsic efficiency and specific output energy have been increased by approximately 50%, to 1.8% and 3 J/L, respectively, which represent the best performance obtained thus far for any directly electrically excited XeF (C →A ) laser. Also, by injecting a narrowband signal into the cavity, the XeF (C →A ) laser linewidth has been reduced by more than two orders of magnitude, to less than 1.3 Å, the resolution of the spectrometer. The laser wavelength has been tuned from 478.6 to 486.8 nm, with less than a factor of two variation in output energy 相似文献
11.
Yamashita S. Oka A. Kawano T. Tsuchiya T. Saitoh K. Uomi K. Ono Y. 《Photonics Technology Letters, IEEE》1992,4(9):954-957
A low-threshold 1.3-μm InGaAsP MQW laser array was fabricated on a p-type InP substrate taking compatibility with n/p/n-type laser-driver circuits into account. The laser has a p/n-type current-blocking structure and is made entirely by metal-organic chemical vapor deposition (MOCVD). A 10-channel laser array with a threshold current as low as 3.2±0.2 mA (per element) and a slope efficiency of 0.27±0.01 W/A is obtained 相似文献
12.
Soo Young Yoon Young N. van der Zaag P.J. McCulloch D. 《Electron Device Letters, IEEE》2003,24(1):22-24
High-performance polycrystalline silicon (poly-Si) thin-film transistors (TFTs) have been fabricated using metal-induced crystallization followed by laser annealing (L-MIC). Laser annealing after MIC was found to yield a major improvement to the electrical characteristics of poly-Si TFTs. At a laser fluence of 330 mJ/cm/sup 2/, the field effect mobility increased from 71 to 239 cm/sup 2//Vs, and the minimum leakage current reduced from around 3.0/spl times/10/sup -12/ A//spl mu/m to 2.9/spl times/10/sup -13/ A//spl mu/m at a drain voltage of 5 V. In addition, the dependence of the TFT characteristics on the laser energy density was much weaker than that for conventional excimer laser annealed poly-Si TFTs. 相似文献
13.
In this work, we report new optically pumped far-infrared (FIR) laser lines from CHD/sub 2/OH. A waveguide CO/sub 2/ laser of wide tunability (290 MHz) was used as pump source, and a Fabry-Pe/spl acute/rot open cavity was used as a FIR laser resonator. Optoacoustic absorption spectra were used as a guide to search for new FIR laser lines. We could observe 15 new laser lines in the range from 116.4 to 401.4 /spl mu/m. The lines were characterized according to wavelength, relative polarization, relative intensity, and optimum working pressure. The transferred Lamb-dip technique was used to measure the frequency absorption transition both for the new and previously reported laser lines. 相似文献
14.
L. Shterengas G.L. Belenky A. Gourevitch D. Donetsky J.G. Kim R.U. Martinelli D. Westerfeld 《Photonics Technology Letters, IEEE》2004,16(10):2218-2220
High-power 2.3-/spl mu/m In(Al)GaAsSb-GaSb type-I double quantum-well diode laser arrays were fabricated and characterized. Linear laser arrays with 19 100-/spl mu/m-wide elements on a 1-cm-long bar generated 10 W in continuous-wave (CW) mode and 18.5 W in quasi-CW mode (30 /spl mu/s/300 Hz) at a heatsink temperature of 18/spl deg/C. Array power conversion efficiency peaked at 30 A and was about 9%. Device internal efficiency was about 50%. Individual laser differential gain with respect to current was about twice as high as in InP-based laser heterostructures, demonstrating the potential of GaSb-based material system for high-power CW room-temperature laser diode arrays. 相似文献
15.
Biemacki P.D. Frankel M.Y. Gingerich M.E. Matthews P.J. 《Lightwave Technology, Journal of》1999,17(7):1222-1228
A mixed digital-to-analog (D/A) high speed circuit board capable of driving a tunable super structure grating distributed Bragg reflector (DBR) laser is developed. The circuit is used to control the laser over a 20-nm tuning wavelength range with 0.1 nm resolution. Three control currents are preprogrammed into an electrically erasable/programmable read-only memory (EEPROM) look-up table for each wavelength. Upon receiving a differential logic control signal, the circuit tunes the laser to the specified output wavelength within 500 ns. The long-term repeatability of the tuned laser output wavelength shows drift below ±0.02 nm with greater than 100 h of operation 相似文献
16.
Shinoda K. Kitatani T. Aoki M. Mukaikubo M. Uchida K. Uomi K. 《Photonics Technology Letters, IEEE》2006,18(22):2383-2385
We present a novel 1.3-mum laser, a short-cavity distributed-Bragg-reflector (DBR) laser that enables uncooled, 10-Gb/s operation with low drive currents. The laser consists of a short InGaAlAs multiple-quantum-well active region butt-jointed to an InGaAsP-DBR region. A fabricated laser with a 75-mum active region demonstrated 100 degC, 10-Gb/s operation at a record low drive current of 14-mA peak-to-peak (mAp-p) with an average output power of -3 dBm 相似文献
17.
Min Cao Talwar S. Kramer K.J. Sigmon T.W. Saraswat K.C. 《Electron Devices, IEEE Transactions on》1996,43(4):561-567
A high-performance polysilicon thin-film transistor (TFT) fabricated using XeCl excimer laser crystallization of pre-patterned amorphous Si films is presented. The enhanced TFT performance over previous reported results is attributed to pre-patterning before laser crystallization leading to enhanced lateral grain growth. Device performance has been systematically investigated as a function of the laser energy density, the repetition rate, and the number of laser shots. Under the optimal laser energy density, poly-Si TFT's fabricated using a simple low- temperature (⩽600°C) process have field-effect mobilities of 91 cm2/V·s (electrons) and 55 cm2/V·s (holes), and ON/OFF current ratios over 10 7 at VDs=10 V. The excellent overall TFT performance is achieved without substrate heating during laser crystallization and without hydrogenation. The results also show that poly-Si TFT performance is not sensitive to the laser repetition rate and the number of laser shots above 10 相似文献
18.
Frequency offset locking was proposed as a reliable electrical negative feedback technique for tracking and sweeping of a semiconductor laser frequency. A frequency stabilized laser was used as a master laser, whose residual frequency fluctuations were 140 (kHz) at the integration time (τ) of 100 msleq tau leq 100 s. A digital phase comparator of a large dynamic range of2pi times 2^{11} (rad) was employed in the feedback loop to reduce the phase fluctuations of the beat signal between the master and slave lasers. Performances of frequency tracking and sweeping of the slave laser were quantitatively evaluated, and the results are: residual frequency fluctuations of the beat signal were reduced as low as 11 (Hz) attau = 100 s, which meant that the residual frequency fluctuations of the slave laser were almost equal to those of the master laser, i.e., the slave laser frequency tracked accurately to the master laser frequency. Both the capture range and lock range of the beat frequency were 1.22 GHz. Frequency tunable range of the slave laser was 36.6 GHz under the condition of frequency offset locking, in which the slave laser frequency fluctuations were maintained as low as the one given above. 相似文献
19.
A copper vapor laser tube with a large volume (15.1 L) has been built for the study of extrapolation in power of the Cu-Ne-HCl-H/sub 2/ laser medium. A high-power (77 kW) all-solid-state high-voltage power supply has been also used for this purpose. Results show an improvement of the optical power after the HCl-H/sub 2/ mixture injection. An optical power of 312 W has been extracted from this laser head in oscillator configuration. 相似文献
20.
Rafferty B.D. Anderson B.T. Glassman J. Miller H.C. Lampson A.I. Hager G.D. 《Quantum Electronics, IEEE Journal of》1997,33(5):685-704
This paper describes the results from a combined experimental theoretical investigation of a coaxial pumped photolytic bromine laser. A 532-nm pump was used to photodissociate IBr and produce Br*(2 P1/2) with subsequent lasing on the (2P1/2)→(2P3/2) transition. Experimental results are presented for output energy, mode buildup time and small-signal gain as a function of pump energy and mirror outcoupling fraction. A simplified rate equation model was developed to predict the laser performance parameters and shows good agreement with the laser output energy and small-signal gain 相似文献