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中国物理学会期刊

静水压力调谐Ag纳米颗粒散射场下量子点激子寿命

CSTR: 32037.14.aps.71.20221344

Exciton lifetime of quantum dots under hydrostatic pressure tuned scattering field Ag nanoparticles

CSTR: 32037.14.aps.71.20221344
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  • 将InAs/GaAs量子点薄膜样品转移到Ag纳米颗粒覆盖的Si衬底上, 然后将样品放到金刚石对顶砧压力腔室内. 在 1.09—1.98\;\rmG\rmP\rma 的压力范围内, 测量了量子点激子的荧光光谱和时间分辨光谱. 实验结果显示, 随着静水压力的增大, 激子的发光波长蓝移, 激子的发光寿命从 \left(41\pm 3\right)\times 10\;\rmn\rms 延长到 \left(120\pm 4\right)\times 10\;\rmn\rms , 再减短到 (7.6\pm 0.2)\;\rmn\rms , 在激子发光波长为 797.49\;\rmn\rmm 时, 寿命达到最长的 \left(120\pm 4\right)\times 10\;\rmn\rms . 相比没有Ag纳米颗粒影响的InAs/GaAs量子点中的激子寿命约 1\;\rmn\rms , 激子的寿命延长了约1200倍. 其物理机制为量子点浸润层中激子的辐射场和Ag 纳米颗粒的散射场之间发生相消干涉, 抑制了浸润层中激子的自发辐射, 这些长寿命的浸润层激子将扩散到量子点中, 并辐射复合发光, 从而观察到量子点激子的长寿命衰变曲线. 这一实验结果与基于在散射场下的偶极子辐射模型计算结果一致.

     

    In the past few decades, the studies of exciton emissions coupled with the metal nanoparticles have mainly focused on the enhancing exciton radiation and reducing exciton lifetime by near-field coupling interactions between excitons and metal nanoparticles. Only in recent years has the plasmon-field-induced to extend exciton lifetime (inhibition of the exciton emission) been reported. Experimentally, for observing a long-lifetime exciton state it needs to satisfy a condition of kz\sim1, instead of near-field condition of kz\ll 1 , where k=2\pi n/\lambda is the wavevector, n is the refractive index, \lambda is the wavelength, and z is the separation distance between the emitter and metal nanoparticle. Thus, in this paper, we tune the exciton emission wavelength by applying hydrostatic pressure to achieve the condition of kz\sim1 in order to in detail investigate the coupling between excitons and metal nanoparticles. The studied InAs/GaAs quantum dot (QD) sample is grown by molecular beam epitaxy on a (001) semi-insulating GaAs substrate. After the AlAs sacrificial layer is etched with hydrofluoric acid, the QD film sample is transferred onto an Si substrate covered with Ag nanoparticles. Then the sample is placed in the diamond anvil cell device combined with a piezoelectric ceramic. In this case we can measure the photoluminescence and time-resolved photoluminescence spectra of the QD sample under different pressures. It is found that the observed longest exciton lifetime is (120\pm 4)\times 10~\rmn\rms at a pressure of 1.38\;\rmG\rmP\rma , corresponding the exciton emission wavelength of 797.49\;\rmn\rmm , which is about 1200 times longer than the exciton lifetime of \sim 1\;\rmn\rms in QDs without the influence of Ag nanoparticles. The experimental results can be understood based on the destructive interference between the quantum dot exciton radiation field and the scattering field of metal nanoparticles. This model proposes a convenient way to increase the emission lifetime of dipoles on a large scale, and is expected to be applied to quantum information processing, optoelectronic applications, fundamental physics researches such as Bose-Einstein condensates.

     

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