Fabricate Photonic Crystals Based on ZnS/opal System via Solvothermal Method
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Fabricate Photonic Crystals Based on ZnS/opal System via Solvothermal Method Jieming Cao1, Xin Chang, Lijia Pan, Hongmei Ji, Jinsong Liu, Jie Feng, Fang Zhang, Haiyan Wang, Jie Tao, Guoyue Xu 1 Research Institute of Nanomaterials, College of Material Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, P. R. China ABSTRACT We made photonic crystals composed of artificial opals infiltrated with ZnS semiconductor nanocrystals by using self-assembly and solvothermal methods. Scanning electron microscopy images show that the silica spheres exhibit a well-ordered arrangement and the ZnS nanocrystals grow homogenously inside the opal matrix and the as-synthesized ZnS nanocrystals reveal a cubic phase from X-ray diffraction pattern. Furthermore, the optical properties of the infiltrated opals with different ZnS filling ratio are also studied by transmission spectroscopy respectively. It is proposed that the position of the stop band can be easily designed by controlling the infiltration ratio of ZnS. These results demonstrate an effective and practical route to obtain high-performance photonic crystal structures. INTRODUCTION Photonic crystals (PCs) have attracted considerable attention in the past decade since the original idea was kicked off independently by Yablonovitch [1] and John [2]. PCs promise to become as important to the progress of optical devices as semiconductors were to the development of electronic devices. It is proposed that they will offer many interesting applications in photonics and electronics [1-5]. Colloidal crystals formed from three-dimensionally (3D) ordered lattice of self-assembled monodisperse colloidal spheres with a close-packed face-centred-cubic (FCC) structure named as opals have been shown to be excellent candidates to fabricate 3D photonic bandgap materials [6,7]. Unfortunately, these structures do not have perfectly photonic properties. Photonic behaviour can be enhanced by infiltrated the voids of opals with higher refractive index materials. Recently, some works on various semiconductors and polymer infilled opals were reported [8-11]. As a kind of compound semiconductor, zinc sulphide (ZnS) can be used as an appropriate material for forming PCs due to its high refractive index and large bandgap that makes it highly transparent in the visible and near IR regions. Solvothermal method, which is similar to the hydrothermal method except that organic solvents are used instead of water, was proved to be an effective route to prepare a variety of high-quality chalcogenide semiconductor nanocrystallites [12,13]. In this work, we reported a solvothermal approach for preparing ZnS/opal system. Self-assembled structures of colloidal silica sphere were used as a 3D scaffold and ZnS nanocrystals were grown in the voids of the template by solvothermal route. Solvothermal method offers several advantages over
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previous techniques including homogenous ZnS growth within the opal and high quality of ZnS nanocrystals. The goal of this work is to
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