Ag-Cu离子注入SiO_2玻璃后形成纳米颗粒的研究

Study on nanocavities-containing Ag and Cu nanoparticles produced by sequential ion implantation in silica

Ag、Cu离子经200和110keV加速后分别以5×1016和1.5×1017ions/cm2的剂量在室温下先后注入到非晶SiO2玻璃中。注入后样品的光学吸收谱显示两个吸收峰,其峰位为407和569nm,分别对应单独Ag和单独Cu纳米颗粒的等离子体共振吸收峰,样品在还原-保护气氛下退火后吸收峰峰强明显增加。样品的透射电镜选区电子衍射花样含有Ag、Cu两套衍射环,透射电镜的明场像观察到大量的纳米颗粒呈现出中心亮斑特征。在样品倾转过程中,中心亮斑特征依然存在,证实这种现象是离子辐照产生的纳米空位团簇。扫描透射电子显微镜高角环形暗场像进一步证实了这一点。综上所述,样品中形成了单Ag和单Cu包裹空位团簇的纳米颗粒。

Silica was implanted sequentially with Ag ions at 200 keV to dose of 5 × 10^16 ions/cm^2 and Cu ions at 110keV to dose of 1.5× 10^17 ions/cm^2 respectively. According to the TRIM calculation, the energy of implantation for each ion was chosen to obtain similar ion distribution with considering the surface sputtering effect. Energy dispersive X-ray spectrometry （EDS） of the sample shows the existence of Ag and Cu elements in the sample. The optical absorption spectra show two surface plasmon resonance （SPR） peaks with position of 407 and 569nm, corresponding to the standard SPR peaks of Ag and Cu. The selected area electron diffraction （SAED） of the sample displays two sets of diffraction rings for Ag and Cu. It is interest to be observed by the transmission electron microscope bright-field （TEM-BF） images that most of nanoparticles have brighter center features. The BF images of the same area in the sample,which is obtained by tilting the sample from -40-40 degrees, show that these brighter center features do not change. This indicates that the formation of nanocavitycontained Ag and Cu nanoparticles, not the core-shell nanoparticles as other workers believed. The scanning transmission electron microscopy high-angle annular dark field （STEM-HAADF） image also confirms this standpoint. The nanocavities can be attributed to the aggregation of irradiation-induced vacancies.