【作者】 刘海；

【导师】 白一鸣；

【作者基本信息】 华北电力大学(北京) ， 动力工程（专业学位）， 2016， 硕士

【摘要】 因其独特的光电性质,贵金属纳米颗粒被广泛地应用于太阳电池、发光二极管以及生物传感器等领域。众所周知,纳米颗粒的光电性质与其形貌、尺寸、介电环境、表面覆盖率等因素密切相关。因此,探索贵金属纳米颗粒形貌和尺寸的可控性制备及其性能,特别是物理法制备纳米颗粒,将对其潜在的应用有重要的科学价值。基于此,本文主要开展了Ag和Au纳米颗粒的制备、形成机理及光学性能的研究。本论文采用磁控溅射结合热处理的方法制备了Ag和Au两种贵金属纳米颗粒。重点研究了退火温度、退火方式、介质层对Ag纳米颗粒形貌和光学性能的影响。在Au纳米颗粒的制备方面,首次采用磁控溅射结合热处理的方式制备出单晶正六角Au纳米颗粒。通过研究,主要取得如下成果：1、退火模式对Ag纳米颗粒形貌有着重要影响。原位退火后的Ag纳米颗粒的粒径分布范围较宽,且存在大量粒径小于50 nm的Ag纳米颗粒；而快速热退火后的纳米颗粒尺寸分布相对均匀,呈现出高斯分布的特点。2、原位退火和快速热退火模式下,Ag薄膜的形貌演变遵循不同的机理。采用原位退火和快速热退火方式分别对9 nm厚的Ag膜在200、250、300、400℃进行退火处理。研究发现前者遵循孔洞形核理论,后者则遵从晶界成槽理论。我们认为这是由于原位退火升温速率很慢(0.33℃/min),有利于薄膜中的空位形成孔洞；而快速热退火有较高的升温速率(100℃/s),使Ag膜瞬间获得足够的能量并在晶界处断裂。3、SiO2薄膜厚度对Ag纳米颗粒的陷光性能有着重要影响。研究发现Si02层的引入,会显著改变Ag纳米颗粒的形貌,具体表现为：随着SiO2厚度的增加,Ag纳米颗粒的表面覆盖率会逐渐下降,最低为33.2%,同时平均粒径会随之逐渐上升,最高为68.98 nm。同时光学性能研究发现,引入Si02,Ag纳米颗粒的偶极消光峰会发生红移,最大红移为86.0 nml,但是消光峰的强度却将降低；相对于未引入Si02薄膜的Ag纳米颗粒而言,沉积Si02薄膜的Ag纳米颗粒散射光子数目降低了2×1018。4、采用磁控溅射结合快速热退火的方法,首次制备出了单晶正六角Au纳米柱。研究发现退火温度决定了Au纳米颗粒的形貌。在700、800℃退火温度条件下,7.5 nm的Au薄膜形成的Au纳米棒的纵横比分别为1.8、1.2,当退火温度上升到900℃时,形成了规则的单晶正六角Au纳米柱,并采用能量最低原理的热力学模型解释了不同退火温度下,Au纳米颗粒呈现不同形貌的原因。更多还原

【Abstract】 Noble metallic nanoparticles (NPs) have been paid more attentions and applied extensively in solar cells, light emitting diode and biosensors due to their distinct optical and electrical properties. It is well known that the optical and electrical properties of noble metal NPs depend on the shape, size, refractive index, surface coverage rate and etc. Therefore, preparation of NPs with controllable size and shape, especially by the physical method, is valuable for their potential application. Herein, we performed the study on the fabrication, formation mechanism and optical properties of Ag and Au NPs.In this thesis, Ag and Au NPs were fabricated via magnetron sputtering with subsequent thermal annealing methods, and the influence of processing parameters, such as annealing temperature, annealing modes and dielectric environment, on the shape and optical properties of Ag NPs were investigated. Moreover, single crystalline Au nanoprisms with regular hexagonal shape were firstly fabricated by magnetron sputtering with subsequent rapid thermal annealing treatments. Several works have been developed and following significant results have been attained.1. The morphology of Ag NPs’greatly relies on the annealing modes. The results confirm that the in-situ annealing mode favors the formation of NPs with a great number of small sized NPs (D<50) while the rapid thermal annealing mode is more likely to generate NPs with uniform size and a gauss like size distribution.2. The agglomeration behaviors of Ag films follow different mechanisms when annealed under in-situ and ex-situ treatment process. A comparison study on the shape evolutions of 9 nm-thick Ag films deposited by magnetron sputtering with in-situ heating and ex-situ rapid thermal annealing treatments at different temperatures (200, 250,300,400℃) was exploited, respectively. The former agglomerates via nucleation of voids, and the latter obeys the grain boundary grooving mechanism. We speculate the heating rate plays a key role during the annealing process, namely, the slow heating treatments is favorable for forming of void while the rapid one is beneficial for Ag film gaining enough energy and rupturing at grain boundary.3. The optical properties of Ag NPs greatly rely on the thickness of SiO2 film. Our findings identify that the surface coverage ratio of Ag NPs decreases while the average particle diameter increases as the thickness of SiO2 film increases, and the minimum surface coverage ratio is 33.2% and the maximum average particle diameter is 68.98 nm. The dipole extinction peak of Ag NPs shows a 86.0 nm red shift after introducing SiO2 film, but the peak intensity decreases greatly. Moreover, we found that the scattering number of photons by Ag NPs is decreased by as much as 2x 1018 after inserting a SiO2 layer.4. Single crystalline Au nanoprisms with regular hexagonal shape were firstly fabricated by magnetron sputtering with subsequent rapid thermal annealing treatments. Our results confirm that the morphology of Au NPs greatly depends on the annealing temperature. Au nanorods with aspect ratio of 1.8 and 1.2 are produced respectively for a 7.5 nm Au film annealed at 700 and 800℃. When the annealing temperature increases to 900℃, Au regular hexagonal nanoprisms are formed, and a thermodynamic model is adopted to explain the shape transition of Au NPs.更多还原