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Zno纳米晶的室温紫外受激发射特征 总被引:2,自引:0,他引:2
ZnO的激子特性对制备氧化锌基的光电子器件至关霞要,因此对ZnO量子点中激子的发光性质及其跃迁过程进行研究显得十分必要.采用溶胶-凝胶法制备了ZnO纳米晶,X射线衍射(XRD)结果表明样品具有六角纤锌矿多晶结构.研究了在不同泵浦功率激发下ZnO纳米晶的紫外发射的时间积分光谱和时间分辨光谱,观察到自南激子发光,激子-激子碰撞和电子-空穴等离子体引起的受激发射,研究了在不同泵浦功率激发下自由激子及激子-激子碰撞随泵浦功率依赖的动力学过程.研究结果对理解激子带边发射有一定帮助,对ZnO材料在短波长半导体光电器件方面有潜在的应用价值. 相似文献
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在水相合成CdTe以及CdTe/CdS核壳结构量子点基础上, 利用基于抽运-探测技术的瞬态差分透射技术研究了CdTe量子点以及不同CdS壳层厚度的CdTe/CdS量子点的最低激子能态的超快激发与弛豫动力学. 研究表明:相比于CdTe,CdTe/CdS量子点的电子空穴由于空间分离,其所需的激发时间要长于电子空穴空间重叠态所需要的激发时间.随着壳层厚度的增加, 量子点表面的钝化有效地减少了表面态相关弛豫机理,并延长相对应的弛豫时间. 相似文献
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报道了以飞秒脉冲激光为激发光源的水溶性CdTe量子点(QDs)的稳态荧光光谱和纳秒时间分辨荧光光谱.实验发现CdTe量子点的荧光光谱峰值位置随激发波长变化发生明显移动,激发脉冲波长越长,荧光峰位红移越大.荧光动力学实验数据显示,在400nm和800nm脉冲激光激发下,水溶性CdTe量子点的荧光光谱中均含有激子态和诱捕态两个衰减成分,两者的发射峰相距很近,诱捕态的发射峰波长较长.在800nm脉冲激光激发下的诱捕态成分占总荧光强度的比重比400nm激发下的约高3倍,其相对强度的这种变化导致了稳态荧光发射峰位的红移.
关键词:
CdTe 量子点
时间分辨
荧光光谱
上转换荧光 相似文献
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本文将基于有效质量近似下的变分法,理论研究了纤锌矿InGaN/GaN staggered量子阱中的激子态和光学性质.数值结果显示了InGaN量子阱中的量子尺寸和staggered受限垒对束缚于量子阱中的激子态和光学性质有着明显的影响.当阱宽增加时,量子受限效应减弱,激子结合能降低,带间发光波长增加.另一方面,当量子阱中staggered受限势增加时,量子受限效应增强,激子结合能升高,带间发光波长降低.本文的理论结果证明了可以通过调节staggered垒高和量子尺寸来调控纤锌矿InGaN staggered量子阱中的激子态和光学性质. 相似文献
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R. Heitz I. Mukhametzhanov O. Stier A. Madhukar D. Bimberg 《Physica E: Low-dimensional Systems and Nanostructures》2000,7(3-4)
Phonon-assisted exciton transitions are investigated for self-organized InAs/GaAs quantum dots (QDs) using selectively excited photoluminescence (PL) and PL excitation spectroscopy. The results unambiguously demonstrate intrinsic recombination in the coherent InAs/GaAs QDs and the absence of a Stokes shift between ground state absorption and emission. Phonon-sidebands corresponding to a phonon energy of 34 meV are resolved and Huang–Rhys parameters of 0.015 and 0.08 are found for phonon-assisted emission and absorption, respectively, which are about one order of magnitude larger than in bulk InAs. Calculations of the exciton–LO–phonon interaction based on an adiabatic approximation and realistic wave functions for ideal pyramidal InAs/GaAs QDs show this enhanced polar coupling to result from the particular confinement and the strain-induced piezoelectric potential in such strained low-symmetry QDs. 相似文献
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测定了亚单层InGaAs/GaAs量子点-量子阱异质结构在5K下的时间分辨光致发光谱.亚单层量 子点的辐射寿命在500 ps 至 800 ps之间,随量子点尺寸的增大而增大,与量子点中激子的 较小的横向限制能以及激子从小量子点向大量子点的隧穿转移有关.光致发光上升时间强烈 依赖于激发强度密度.在弱激发强度密度下,上升时间为 35 ps,纵光学声子发射为主要的 载流子俘获机理.在强激发强度密度下,上升时间随激发强度密度的增加而减小,俄歇过程 为主要的载流子俘获机理.该结果对理解亚单层量子点器件的工作特性非常有用.
关键词:
亚单层
量子点-量子阱
时间分辨光致发光谱 相似文献
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Tetyana V. Torchynska 《Journal of luminescence》2012,132(8):1848-1852
The paper presents the original study of photoluminescence (PL) and Raman scattering spectra of core–shell CdSe/ZnS quantum dots (QDs) covered by the amine-derivatized polyethylene glycol (PEG) with luminescence interface states. First commercially available CdSe/ZnS QDs with emission at 640 nm (1.94 eV) covered by PEG polymer have been studied in nonconjugated states. PL spectra of nonconjugated QDs are characterized by a superposition of PL bands related to exciton emission in a CdSe core and to the hot electron–hole recombination via high energy luminescence states. The study of high energy PL bands in QDs at different temperatures has shown that these PL bands are related to luminescence interface states at the CdSe/ZnS or ZnS/polymer interface. Then CdSe/ZnS QDs have been conjugated with biomolecules—the Osteopontin antibodies. It is revealed that the PL spectrum of bioconjugated QDs changed essentially with decreasing hot electron–hole recombination flow via luminescence interface states. It is shown that the QD bioconjugation process to Osteopontin antibodies is complex and includes the covalent and electrostatic interactions between them. The variation of PL spectra due to the bioconjugation is explained on the basis of electrostatic interaction between the QDs and biomolecule dipoles that stimulates re-charging QD interface states. The study of Raman scattering of bioconjugated CdSe/ZnS QDs has confirmed that the antibody molecules have the electric dipoles. It is shown that CdSe/ZnS QDs with luminescence interface states are promising for the study of bioconjugation effects with specific antibodies and can be a powerful technique in biology and medicine. 相似文献
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半导体量子点(QDs)具有发光效率高和发光波长可调等特点。采用胶体CdSe QDs作电致发光器件的有源材料,TPD(N,N′-biphenyl-N,N′-bis-(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine)作空穴传输层,ZnS作电子传输层,研究了有机/无机复合发光器件ITO/TPD/CdSe QDs/ZnS/Ag的电致发光特性。TPD和CdSe QDs薄膜采用旋涂方法、ZnS薄膜采用磁控溅射方法沉积,器件表面平整。CdSe QDs的光致发光和电致发光谱峰位波长均位于~580 nm,属于量子点的带边激子发光。我们与以前的ITO/ZnS/CdSe QDs/ZnS/Ag发光器件结构进行了对比,发现新的器件结构的电致发光谱没有观察到QDs表面态的发光,而且新器件的发光强度是ITO/ZnS/CdSe QDs/ZnS/Ag结构的~10倍。发光效率的提高归因于碰撞激发与载流子注入两种发光机制并存的结果:一方面电子经过ZnS 层加速后,碰撞激发CdSe QDs发光;另一方面,空穴从TPD层注入CdSe QDs 与QDs中激发的电子复合发光。我们进一步研究了ZnS电子加速层厚度对发光特性的影响,选择ZnS薄膜的厚度分别是80,120 和160 nm,发现随着ZnS层厚度增大,器件启亮电压升高,EL强度增大,但是击穿电压降低。EL峰位随着ZnS厚度的减小发生明显蓝移,对上述实验现象进行了机理解释。 相似文献
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Based on the framework of effective-mass approximation and variational approach, optical properties of exciton are investigated theoretically in ZnO/MgxZn1−xO vertically coupled quantum dots (QDs), with considering the three-dimensional confinement of electron and hole pair and the strong built-in electric field effects due to the piezoelectricity and spontaneous polarization. The exciton binding energy, the emission wavelength and the oscillator strength as functions of the different structural parameters (the dot height and the barrier thickness between the coupled wurtzite ZnO QDs) are calculated with the built-in electric field in detail. The results elucidate that structural parameters have a significant influence on the exciton state and optical properties of ZnO coupled QDs. These results show the optical and electronic properties of the quantum dot that can be controlled and also tuned through the nanoparticle size variation. 相似文献
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采用双层耦合量子点的分子束外延生长技术生长了InAs/GaAs量子点样品,把量子点的发光波长成功地拓展到1.3 μm.采用光刻的工艺制备了直径为3 μm的柱状微腔,提高了量子点荧光的提取效率.在低温5 K下,测量得到量子点激子的荧光寿命约为1 ns;单量子点荧光二阶关联函数为0.015,显示单量子点荧光具有非常好的单光子特性;利用迈克耳孙干涉装置测量得到单光子的相干时间为22 ps,对应的谱线半高全宽度为30 μeV,且荧光谱线的线型为非均匀展宽的高斯线型. 相似文献
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Electrically driven single photon source based on single InAs quantum dot (QDs) is demonstrated. The device contains InAs QDs within a planar cavity formed between a bottom AlCaAs/CaAs distributed Bragg reflector (DBR) and a surface CaAs-air interface. The device is characterized by I-V curve and electroluminescence, and a single sharp exciton emission line at 966nm is observed. Hanbury Brown and Twiss (HBT) correlation measurements demonstrate single photon emission with suppression of multiphoton emission to below 45% at 80 K 相似文献
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《Physica E: Low-dimensional Systems and Nanostructures》2011,43(10):2509-2513
Intensity correlation measurements on single InP/GaInP quantum dots (QDs) show antibunching at zero delay time, indicative of single photon emission. The antibunching time τR increases or decreases with temperature depending on the QD size as a result of the competition between: (1) thermal excitation of holes dominant in smaller QDs and (2) dark-to-bright exciton transition dominant in larger QDs. The antibunching minimum g(2)(0) remains below 0.2 up to 45 K. 相似文献
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利用飞秒脉冲激光激发Cu掺杂ZnO纳米棒,研究其特有的非线性光学性质和激发机制。在激发波长为750 nm的荧光光谱中,二次谐波峰非常弱,几乎可以忽略,存在非常强的激子发光峰和Cu掺杂导致缺陷发光峰。激发强度的增大会导致这两个发光峰强度呈非线性增大,激子发光峰位产生明显红移,而缺陷发光峰位没有变化。进一步增大激发强度,缺陷发光峰强度会出现饱和甚至有所下降,而激子发光峰强度持续增大。当激发波长增加到760 nm时,从样品的荧光光谱可以清楚地识别到二次谐波峰和激子发光峰以及缺陷发光峰并存。随着激发波长的进一步增加,二次谐波强度不断增大,而激子发光峰和缺陷发光峰的强度却随之下降。当激发波长为790 nm和800 nm时,未发现激子发光峰和缺陷发光峰,非线性光谱以二次谐波为主导。研究结果表明,通过选择合适的激发波长和激发强度,可以实现发光颜色的转变,使得Cu掺杂ZnO纳米棒在全光显示方面具有潜在的发展前景。 相似文献
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Laser-excited techniques were used to investigate the optical properties of bismuth germanate crystals. Absorption, reflectivity, excitation, emission, lifetime, time-resolved fluorescence, photoconductivity, thermally stimulated conductivity measurements were performed at various temperatures on single crystals of different origins.The absorption is shown to occur in bismuth and germanate centers while both intrinsic and perturbed Bi3+ ions together with impurities contribute to the total fluorescence.The emission mechanism at room temperature involves a thermally activated energy migration, and at low temperature localized emitting centers. Formation of deep holes in the wide emission band at room temperature reveals saturation effects on various luminescent centers, promoted by energy migration. Trapped exciton models are proposed to explain the excited state dynamics occurring at low and room temperature. 相似文献