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通过理论模拟对具有上覆盖层的SiO2脊形条波导结构进行了优化,在此基础上利用微电子工艺制作了SiO2脊形波导Mach-Zehnder型电光调制器,并进行热极化引起的电光和非线性效应的研究.热极化过程大幅增强了样品的电光及非线性效应,二次电光系数由热极化前的1.56×10-22(m/V)2提高到热极化后的8.50×10-22(m/V)2,极化后得到了0.093pm/V的线性电光系数,对热极化的物理机理进行了理论分析.
关键词:
电光调制器
2光波导')" href="#">SiO2光波导
电光效应
热极化 相似文献
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Tm3+掺杂SrAl2O4:Eu2+的光激励和热释光性能 总被引:2,自引:2,他引:0
通过高温固相法制备出Sr0.98-xAl2O4:0.02Eu2+,xTm3+(x=0,0.01,0.02,0.03,0.04,0.05)系列样品,并对其光激励和热释光性能进行了研究。在SrAl2O4:Eu2+原有陷阱能级结构的基础上,通过Tm3+的掺杂引入了更深的陷阱TB,并增加原有陷阱TA浓度,进而优化了材料的光存储容量及光激励特性。对比研究了系列样品的初始光激励发光强度和热释光强度随着Tm3+掺杂量的变化规律,证实陷阱TB为光激励发光提供了有效俘获中心。当Tm3+的掺杂摩尔分数x=0.03时,材料中的陷阱TB的浓度达到最高值,同时光激励发光强度最大。对比Tm3+共掺前后热释光图谱,通过Chen's半宽法计算出了引入陷阱TB的陷阱深度。实验结果证实材料中TB的浓度对其光激励发光性能起着决定性的作用。在980 nm激发下,由深陷阱TB释放出来的电子可以再次被浅陷阱TA俘获,这种浅陷阱TA的再俘获效应在光激励发光过程中表现为光激励余辉现象。 相似文献
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(Sr,Ca)AlSiN3:Eu2+红色荧光粉在热性能和长期使用性能等方面还有一定差距,导致制成的白光LED在长期工作状态下发生光衰和色标漂移,影响了白光LED的品质。为解决这一问题,将微量碱土金属离子和稀土金属离子掺入(Sr,Ca)AlSiN3:Eu2+中,研究其对(Sr,Ca)AlSiN3:Eu2+红色荧光粉热性能和长期使用性能的影响。实验结果表明:Li+-Dy3+、Li+-Ho3+等碱土金属-稀土金属离子对(Sr,Ca)AlSiN3:Eu2+红色荧光粉的光衰性能有较明显的提升,同时也显著减小了制灯后长时点亮的色漂移。 相似文献
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采用脉冲激光沉积法制备了La0.88Te0.12MnO3(LTMO)/Si异质结,该异质结具有光生伏特效应和良好的整流特性.光生电压在394 μs的时间内很快增加到最大值然后逐渐减小.在T=80 K时,光生电压的最大值大约是13.7 mV.随着温度的升高,热涨落致使光生电压最大值总体呈现减小趋势,而且是非线性减小,这主要是由LTMO层发生金属绝缘体转变而导致的LTMO层能带结构的变化引起的.
关键词:
异质结
光生伏特效应
电子掺杂 相似文献
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采用高温固相反应法制备了一系列MgAl2O4∶xMn2+。在450 nm的蓝光激发下,观察到了Mn2+的4T1→6A1跃迁的绿色发光,发射光在x=10%时达到最大值。研究结果表明,在x>10%之后,材料的发光强度没有明显减弱。发光强度的减弱是由于Mn2+导致的缺陷增多引起的。缺陷态与Mn2+对于蓝色激发光进行竞争,并且对520 nm的发射光有再吸收过程。温度升高后的发光增强也被观察到。通过变温漫反射谱研究,我们认为这与充当电子陷阱的缺陷态在高温下内部电子被热激发有关。 相似文献
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以ZnO和HGaO2为原料,用不同配比合成出系列ZnGa2O4,并对其晶体结构和发光性能进行了研究。用荧光分光光度计检测了ZnGa2O4的激发和发射光谱,用X射线衍射仪检测了ZnGa2O4的衍射图谱,用热重差热仪绘制了TGA-DAT曲线。对检测结果分析认为:1.ZnGa2O4属于尖晶石结构,稍过量的Zn或Ga能进入ZnGa2O4结构中,并对ZnGa2O4的晶格常数产生一定影响。2.ZnGa2O4存在两个自激发光中心,当Ga稍过量时,自激发光中心是四面体镓氧键[Td(Ga-O)],最大激发波长约248nm,最大发射波长约367nm;当Zn稍过量时,自激发光中心是八面体镓氧键[Oh(Ga-O)],最大激发波长约270nm,最大发射波长约441nm。当n(Zn):n(Ga)在理论值附近,激发和发射光强度最大,而且光谱峰位发生了红移。3.ZnGa2O4的热稳定性能非常好。上述结论对研究ZnGa2O4基质或掺杂的发光材料具有一定意义。 相似文献
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Investigation of Interfacial Charge Separation at PbS QDs/(001) TiO2 Nanosheets Heterojunction Solar Cell
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Elham Ghadiri Bin Liu Jacques‐E. Moser Michael Grätzel Lioz Etgar 《Particle & Particle Systems Characterization》2015,32(4):483-488
In the recent years, the heterojunction solar cells based on quantum dots (QDs) have attracted attention due to strong light absorbing characteristics and the size effect on the bandgap tuning. This paper reports on the kinetics of interfacial charge separation of PbS QDs/(001) TiO2 nanosheets heterojunction solar cells. PbS QDs are deposited using a bifunctional linker molecule on two different TiO2 films, i.e., TiO2 nanosheets (with 001 dominant exposed facet) and TiO2 nanoparticles (with 101 dominant exposed facet). Upon bandgap excitation, electrons are transferred from the PbS QDs conduction band to the lower lying conduction band of TiO2. Based on the ultrafast pump‐probe laser spectroscopy technique, the kinetics of charge separation is scrutinized at the PbS/TiO2 interface. The interfacial charge separation at PbS/TiO2 nanosheets films made of (001) dominant exposed facets is five times faster than that on (101) dominant exposed facets TiO2 nanoparticles. The quantum yields for charge injection are higher for the (001) TiO2 nanosheets than the (101) TiO2 nanoparticles due to enhanced interfacial interaction with (001) surface compared to the (101) nanoparticles. The superior interfacial charge separation at PbS/(001) nanosheets respect to PbS/(101) nanoparticles is consistent with the higher photocurrent and enhanced power conversion efficiency in the PbS QDs/(001) TiO2 heterojunction solar cell. The use of (001) TiO2 nanosheets can be a better alternative to conventional mesoporous TiO2 films in QD heterojunction solar cells and perovskites‐based heterojunction solar cells. 相似文献
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《Ultrasonics sonochemistry》2014,21(2):892-900
Lead sulfide (PbS) quantum dots stabilized by 1,2-benzenedimethanethiol can be synthesized by mixing Pb(NO3)2 and Na2S solutions in ethanol under ultrasound irradiation. The PbS quantum dots (2.7 and 3.6 nm in diameter) are characterized by their absorption and fluorescence spectra in the near infrared region and by other surface analytical techniques. With addition of single-walled carbon nanotubes (SWNT) to the system, this ultrasound-assisted procedure allows attachment of PbS nanoparticles to SWNT surface via π–π stacking, thus providing a simple one-pot method for preparation of SWNT–PbS nanoparticle composite materials. Using the ultrasound-assisted method for synthesizing silica composites containing PbS nanoparticles by a sol–gel process is also described. 相似文献
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Debao WangDabin Yu Maosong MoXianming Liu Yitai Qian 《Solid State Communications》2003,125(9):475-479
The preparation of one-dimensional assemblies of PbS nanoparticles is described. By treating the suspension of PbCl2 powders in aqueous thioacetamide solution at 120 °C for 18 h, PbS nanoparticles were synthesized in regular chain-like patterns. The particles were less than 100 nm in sizes, and were organized into micron-length assemblies. The starting agents have much influence on the morphology of the products. The possible growth mechanism is also discussed. 相似文献
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A. N. Abdrshin Zh. O. Lipatova E. V. Kolobkova E. M. Sgibnev N. V. Nikonorov 《Optics and Spectroscopy》2016,121(6):826-830
PbS molecular clusters and quantum dots are formed by heat treatment in fluorophosphate glasses of the Na2O3–Р2O5–Ga2O3–AlF3–ZnO(S)–PbF2 system with different lead concentrations. PbS molecular clusters are characterized by optical absorption in the range of 300–800 nm and low quantum yields, which decrease from 8.9 to 2.7% with a semiconductor component concentration. It is shown that the parameters of formation of quantum dots luminescing in the wavelength range of 1000–1500 nm are considerably different at different semiconductor component concentrations. The influence of silver ion exchange on the formation of PbS nanoparticles is studied. Introduction of silver stimulates the growth of molecular clusters, which is seen in the absorption spectra. A possible mechanism of interaction of silver nanoparticles with PbS quantum dots is presented. 相似文献
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M.S. Dhlamini O.M. Ntwaeaborwa K.T. Hillie H.C. Swart 《Journal of luminescence》2008,128(12):1997-2003
Thin films of lead sulfide (PbS) nanoparticles embedded in an amorphous silica (SiO2) host were grown on Si(1 0 0) substrates at different temperatures by the pulsed laser deposition (PLD) technique. Surface morphology and photoluminescence (PL) properties of samples were analyzed with scanning electron microscopy (SEM) and a 458 nm Ar+ laser, respectively. The PL data show a blue-shift from the normal emission at ∼3200 nm in PbS bulk to ∼560-700 nm in nanoparticulate PbS powders and thin films. Furthermore, the PL emission of the films was red-shifted from that of the powders at ∼560 to ∼660 nm. The blue-shifting of the emission wavelengths from 3200 to ∼560-700 nm is attributed to quantum confinement of charge carriers in the restricted volume of nanoparticles, while the red-shift between powders and thin-film PbS nanoparticles is speculated to be due to an increase in the defect concentration. The red-shift increased slightly with an increase in deposition temperature, which suggests that there has been a relative growth in particle sizes during the PLD of the films at higher temperatures. Generally, the PL emission of the powders was more intense than that of the films, although the intensity of some of the films was improved marginally by post-deposition annealing at 400 °C. This paper compares the PL properties of powder and pulsed laser-deposited thin films of PbS nanoparticles and the effects of deposition temperatures. 相似文献
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O.M. Ntwaeaborwa R.E. Kroon T. Dubroca J.-K. Park 《Journal of Physics and Chemistry of Solids》2009,70(11):1438-463
Zinc oxide (ZnO) and lead sulphide (PbS) nanoparticles separately synthesized by a precipitation method were combined by an ex situ route to prepare ZnO-PbS nanocomposites with different molar ratios of ZnO and PbS. The structure and morphology of the ZnO, PbS and ZnO-PbS samples were analyzed with X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). A UV-vis spectrophotometer was used to collect the absorption and 325 nm He-Cd and 488 nm Ar lasers were used to collect the photoluminescence data from the samples. ZnO nanoparticles showed a broad and stable emission peak at ∼570 nm, while a strongly quantum confined emission from PbS nanoparticles was detected at ∼1344-1486 nm. The ZnO-PbS nanocomposites exhibited dual emission in the visible and near-infrared (NIR) regions that is associated with defects and recombination of excitonic centres in the ZnO and PbS nanoparticles, respectively. The PL intensity of the visible emission from the ZnO-PbS nanocomposite was shown to increase when the ZnO to PbS molar ratio was 5:1 and the emission was almost quenched at molar ratios of 1:1 and 1:5. For different molar ratios of ZnO to PbS, the PL intensity of the NIR emission from the ZnO-PbS nanocomposites was more intense than that of PbS nanoparticles. 相似文献
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Chengcheng LiuZhifeng Liu Yabin LiJing Ya Lei ELi An 《Applied Surface Science》2011,257(16):7041-7046
Nanoparticles co-sensitized nanorods were designed and prepared by assembled CdS and PbS nanoparticles over ZnO nanorods using successive ionic layer adsorption and reaction (SILAR) method. The results showed that the uniform CdS and PdS nanoparticles could be deposited on the lateral and top of the ZnO nanorods when the precursor concentration was 0.05 M and 0.02 M, respectively. Solar cells based on CdS and PbS nanoparticles sensitized ZnO nanorods arrays were assembled successfully. A cell efficiency of 0.38% was obtained in ZnO/CdS/PbS in comparison with ZnO/PbS/CdS mainly due to the stepwise band edge structure constructed in this system except the coverage density of nanoparticles. 相似文献
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The microstructure and crystal structure of nanocrystalline powders and nanostructured films of lead sulfide PbS have been investigated using X-ray diffraction and electron microscopy. It has been found that, in the synthesized nanopowders, the average size of PbS nanoparticles ranges from 20 to 8 nm, whereas the average size of PbS nanoparticles in nanofilms varies from 80 to 40 nm. It has been shown that the nanocrystalline PbS powders have a cubic (space group $Fm\bar 3m$ ) structure of the B1 type. The nanostructured PbS films prepared by chemical precipitation on a glass substrate have a cubic (space group $Fm\bar 3m$ ) structure of the D03 type with the S atoms located in positions of two types: 4(b) and 8(c). 相似文献
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Daniel J. Asunskis 《Surface science》2007,601(19):4648-4656
Valence band and core level X-ray photoelectron spectroscopy (XPS) were used to probe lead sulfide (PbS) nanoparticle-polymer nanocomposites. Composite materials were prepared by trapping commercially available monodisperse 3 and 10 nm PbS nanoparticles in two polymers, the non-conducting polymer, polystyrene, and the conjugated polymer, poly(2-methoxy-5-(2′-ethyl-hexyloxy)-p-phenylene vinylene (referred to below as MEH-PPV). The nanocomposites prepared from commercial nanoparticles underwent oxidation, mainly to form lead sulfate. However, the narrow size distributions of the commercial nanoparticles allowed observation of distinct changes in the valence band from the 3 to 10 nm nanoparticles. Nanocomposites of 2-5 and 4-7 nm PbS nanoparticles were synthesized by growing the particles in poly(vinyl alcohol) (referred to below as PVA) and MEH-PPV, respectively. These composites both indicated the formation of lead sulfide nanoparticles. Furthermore, the XP spectra for the PVA/PbS composite displayed bonding between the PbS nanoparticles and the polymer while MEH-PPV showed no PbS-polymer bonding. The nanoparticles synthesized in MEH-PPV did not undergo oxidation. The particle size distributions of the synthesized nanoparticles were too broad to display size-dependent changes in the valence band. 相似文献
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In this paper, ultrasonic irradiation was applied for the synthesis of K2Ti6O13 nanobelts and novel nanocomposite (PbS–CdS/Ti6O13) through ion exchanging and co-intercalation processes. Thirty minutes of ultrasonic irradiation caused the formation of pure, uniform potassium hexatitanate with smaller particle size. The incorporation of PbS and CdS nanoparticles into the layers and on the surface of titanate in the presence of ultrasound was done directly, without pre-treatment process and led to the preparation of new nanocomposite. The physicochemical properties of the layered K2Ti6O13 and PbS–CdS/Ti6O13 nanocomposite were analyzed by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), ultraviolet–visible spectra (UV–vis), Fourier transform infrared spectroscopy (FTIR) and photoluminescence technique (PL). The results showed that the PbS–CdS/Ti6O13 possessed a higher interlayer spacing than that of K2Ti6O13, which indicated the formation of an intercalated nanomaterial. Besides that the absorption edge of titanate shifted to the visible light region owing to the incorporation of semiconductor guest molecules. These characteristics make these nanocomposites promising for use as photocatalysts. Besides that, other samples were synthesized by stirring method at the same conditions and their characteristics were compared with sono-synthesized samples. 相似文献