半导体量子点与金属纳米结构的光学响应及其相互作用

发布时间：2018-01-19 05:17

本文关键词： 半导体量子点金属纳米晶体表面等离激元光致发光二次谐波三阶非线性　出处：《武汉大学》2016年博士论文　论文类型：学位论文

【摘要】：纳米材料与其对应的块材相比有着奇特的性质。例如,半导体量子点有着更强的激子限域,并且它们的光学行为可以通过调节尺寸和掺杂物来调节；由于表面等离激元共振,金属纳米结构显示出强的局域场增强,而等离激元共振可以通过控制尺寸和形状来调节。半导体量子点和金属纳米颗粒都有着巨大增强的非线性响应。此外,在纳米尺度上有效的激发能量转移对提高复合纳米材料的光学性质有着极其显著的作用。在这篇毕业论文中,我们研究了Ag掺杂CdTe半导体量子点和金属纳米颗粒的线性以及非线性光学响应,具体研究内容见如下五个方面：第一,我们首次报道了利用水热法合成水溶性Ag掺杂CdTe半导体量子点。实验结果表明Ag杂质能够有效地掺杂到CdTe半导体量子点中。当Ag掺杂浓度为0.3%时,CdTe:Ag量子点的Stokes位移减小了120 meV、荧光强度提高了3.5倍、辐射速率增强了4.2倍,并且非辐射速率被有效地抑制。这些实验结果揭示了CdTe:Ag半导体量子点的荧光增强是由于掺杂Ag导致量子点表面缺陷的减小、缺陷态的填充和辐射速率的增强。我们的结果表明掺杂银是调节CdTe半导体量子点光学性质的一种有效方法。第二,我们研究了重掺杂CdTe:Ag量子点光学三阶非线性特性以及对应的品质因子。在重掺杂银之后,激子共振吸收增强,1S峰红移并且显著展宽。有趣的是,激子带边附近的非线性折射增强了35倍,同时在单光子饱和吸收和双光子带边激发交界的反转处非线性吸收保持很小,从而满足了全光波导开关对单光子和双光子品质因子的需求。我们的研究结果提供了一种方法来制备重掺杂半导体量子点,该量子点具有巨大的三阶极化率和良好的非线性品质因子,在光学信息过程、开关和调制中有非常重要的应用价值。第三,我们展示了Au原子团簇和纳米颗粒耦合体系的可调非线性吸收特性。由于该复合纳米结构中的共振能量转移,SA→RSA过程被有效地抑制,从而观测到SA→SA过程。我们的研究结果提供了一种制备饱和吸收复合纳米材料的新途径,在液态激光器和单光子非线性纳米器件中有应用价值。第四,我们利用溅射技术制备了Ag, Ag/Ag2O和Ag/Ag2O/Ag半球状核壳纳米颗粒,研究了其可调的等离激元共振和二次谐波增强以及上转换发光。近逾渗的Ag/Ag2O/Ag核壳纳米颗粒的二次谐波和上转换发光分别增强了2.34倍和3.94倍。初始半球状Ag纳米颗粒的二次谐波的p偏振和s偏振的强度比(Ip/Is)为0.86,Ag/Ag2O/Ag核壳的Ip/Is增加到1.61。我们的研究结果提供了一种调节二次谐波和上转换发光强度的新方法,在基于等离激元增强的光学非线性纳米器件中具有重要的应用价值。第五,我们对比研究了Au纳米颗粒和原子团簇在水溶液和旋涂薄膜中对CdSe半导体量子点的荧光淬灭效应。在水溶液中,Au纳米颗粒比原子团簇具有更明显的淬灭效应。而在薄膜中,Au原子团簇可以达到与Au纳米颗粒大约相同的淬灭因子。通过研究荧光发射动力学特性发现,Au纳米颗粒会同时增强半导体量子点的辐射和非辐射速率,但是Au原子团簇只增强半导体量子点的非辐射速率。这些观测结果有助于我们理解等离激元的量子特性。
[Abstract]:Nano materials and their corresponding bulk compared with strange properties. For example, semiconductor quantum dots have stronger exciton confinement, and their optical behavior can be adjusted by adjusting the size and dopant; due to surface plasmon resonance, metal nanostructures show strong local field enhancement, and plasmon the resonance element can be adjusted by controlling the size and shape of semiconductor quantum dots and metal nanoparticles have great nonlinear response enhancement. In addition, the nano scale effective excitation energy transfer of composite nano material optical properties have a very significant role. In this thesis, we study the Ag doped CdTe semiconductor quantum dots and metal nanoparticles of the linear and nonlinear optical response, the specific research contents five aspects as follows: first, we first reported by hydrothermal method Synthesis of water soluble Ag doped CdTe semiconductor quantum dots. The experimental results show that Ag can effectively impurity doped CdTe semiconductor quantum dots. When the concentration of Ag is 0.3%, Stokes displacement of CdTe:Ag quantum dots is reduced by 120 meV, the fluorescence intensity increased by 3.5 times, 4.2 times the rate of radiation enhancement, and non radiation rate is effectively suppressed. These results reveal that the fluorescence of CdTe:Ag semiconductor quantum dots doped Ag enhancement is due to decrease of quantum dots surface defects, defect filling and radiation enhancement rate. Our results show that the doped silver is an effective method to adjust the optical properties of CdTe semiconductor quantum dots. Second, we study heavily doped CdTe:Ag quantum dots three order nonlinear optical characteristics and corresponding quality factor. In the heavily doped silver after the exciton resonance absorption enhancement, 1S peak red shifted and widened obviously. Interestingly, shock Subband enhancement nonlinear refraction near 35 times, while the single photon and two-photon saturable absorption band edge at the junction of the nonlinear inversion excitation absorption is very low, so as to meet the optical waveguide switch of single photon and two-photon quality factor demand. Our results provide a method for the preparation of a heavily doped semiconductor quantum dots, the quantum dots with three order of huge polarization rate and good nonlinear quality factor, in the optical information process, has very important application value and switch modulation. Third, we show the adjustable nonlinear absorption properties of Au atomic clusters and nanoparticles due to the resonance energy coupling system. The nano composite structure of the transfer, SA and RSA processes are effectively suppressed, and thus the observed SA and SA. Our results provide a new way for preparation of saturated absorption composite nano materials, in Application of liquid laser and single photon nonlinear nano devices. Fourth, we use the technique of sputtered Ag was prepared. Ag/Ag2O and Ag/Ag2O/Ag hemispherical core-shell nanoparticles, studied the tunable plasmon resonance is enhanced and two harmonics and upconversion. Two harmonic Ag/Ag2O/Ag core-shell nanoparticles in the percolation and upconversion luminescence were enhanced by 2.34 times and 3.94 times. The two harmonic initial hemispherical Ag nanoparticles P polarized and S polarized intensity ratio (Ip/Is) 0.86, Ag/Ag2O/Ag core-shell Ip/Is increased to 1.61. our research results provide a new method for adjusting two times the harmonic and the intensity of upconversion luminescence, based on optical nonlinear plasmonic nano devices in the enhanced has important application value. Fifth, we studied Au nanoparticles and clusters in aqueous solution and spin coating films on CdSe Fluorescence quenching effect in semiconductor quantum dots. In aqueous solution, Au nanoparticles have more obvious quenching than clusters. And the quenching effect in thin films, Au clusters can reach approximately the same Au nanoparticles quenching factor. It is found that the fluorescence emission dynamics, while enhancing the radiation of semiconductor quantum the rate of Au and non radioactive nanoparticles, but Au clusters only enhanced non radiative rate of semiconductor quantum dots. These results can help us to understand the quantum properties of polaritons.

【学位授予单位】：武汉大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O471.1;TB383.1

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