| Surface plasmon resonance (SPR), which originates from the collective oscillation of free-electrons, can be inspired at the metal-dielectric interface under light irradiation. Recently, metal nanorod arrays/ceramic composites have attracted many attentions, because of the structure anisotropy-induced fantastic optical properties. These composites cover a broad range of applications in nonlinear optics, ultrafast optical response, negative refraction, and so on. Currently, the preparation of metal nanorod/ceramic composite films often need a template, and then the nanorod arrays are grown by electrochemical deposition. This method is convenient to prepare well aligned metal nanorod arrays embedded inside the alumina matrix. However, whether the diameter of the nanorods or their spacing distance is in several tens of nanometers scale, or even larger. This undoubtedly leads to that we cannot get access to understanding the exotic SPR features of the nanorod/ceramic composites where both the diameter and spacing of the nanorod arrays are in several nanometers scale, just limited by the template used. On the other hand, the large-scale fabrication on insulating substrates is also a big challenge for the electrochemical deposition method, in which the conductive supporting material is prerequisite.In this thesis, we propose and develop a simple but effective method to prepare ultrafine and dense silver nanowire arrays/alumina composite films. The method is based on RF magnetron co-sputtering technique combining with the substrate bias etching. It is tunable and controllable to modify the size and arrangement of silver nanowires in the composite films. Fox example, the average diameter and spacing distance of the nanowires can be as small as 2 nm. Besides, compared with the electrodepositing method, the magnetron sputtering technique is cost-effective and easy scale up for mass production, independent of substrate materials. Moreover, with no need for adding the revulsant and reducing agents, the sputtering process is environmentally friendly. Based on the success in fabricating composite films with anisotropic microstructure, both the linear spectral response and nonlinear dynamic response can be delicately engineered by adjusting the nanowire diameter and length and the separation between nanowires in the assembly.In this paper, we study the optical properties of the Ag nanowire arrays films by the combination of experiment and simulation. The DDSCAT calculation software is used to simulate the regularity of surface plasmon resonance of the sphere, sphere dimer, cylinder and even nanowire array structure. The influence of the size, shape, environmental media, coupling and other factors on the resonance characteristics of nano structure is understood. The effects of deposition parameters on the silver nanowire arrays are studied, such as the power of silver target deposition, deposition time, bias etching power and so on. The super sensitivity of SPR behavior of silver nanowire arrays to the structural factors such as diameter and spacing is explained. By comprehensive preparation parameters, the L-mode resonance peak of nanowires can be regulated from visible to near infrared range.More interestingly, the fabricated composite films demonstrated ultrafast nonlinear optical response in the visible light region under femtosecond laser excitation, possessing a shorter relaxation time (2 ps) than that of Ag nanoparticles (several tens ps). Through constructing double or three layers array thin film, the wide spectrum ultrafast optical response can be implemented in the visible light range. These results indicate that the proposed composite films as building block with exotic optical properties could provide an opportunity to construct integrated nanodevices for plasmonic optical applications. |
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