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Growth of silicon nanowires-based heterostructures and their plasmonic modeling Yuan Li1, Wenwu Shi1, John C. Dykes3, and Nitin Chopra1,2 1 Metallurgical and Materials Engineering Department, Center for Materials for Information Technology (MINT), The University of Alabama, Tuscaloosa, AL 35487, U.S.A. 2 Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487, U.S.A. 3 REU, Department of Mathematics, The University of Alabama, Tuscaloosa, AL 35487, U.S.A *Corresponding Author E mail: [email protected], Tel: 205-348-4153, Fax: 205-348-2164 ABSTRACT Complex nanoscale architectures based on gold nanoparticles (AuNPs) can result in spatially-resolved plasmonics. Herein, we demonstrate the growth of silicon nanowires (SiNWs), heterostructures of SiNWs decorated with AuNPs, and SiNWs decorated with graphene shells encapsulated gold nanoparticles (GNPs). The fabrication approach combined CVD growth of nanowires and graphene with direct nucleation of AuNPs. The plasmonic or optical properties of SiNWs and their complex heterostructures were simulated using discrete dipole approximation method. Extinction efficiency spectra peak for SiNW significantly red-shifted (from 512 nm to 597 nm or 674 nm) after decoration with AuNPs, irrespective of the incident wave vector. Finally, SiNW decorated with GNPs resulted in incident wave vector-dependent extinction efficiency peak. For this case, wave vector aligned with the nanowire axial direction showed a broad peak at ~535 nm. However, significant scattering and no peak was observed when aligned in radial direction of the SiNWs. Such spatially-resolved and tunable plasmonic or optical properties of nanoscale heterostructures hold strong potential for optical sensor and devices. INTRODUCTION Enhanced light-matter interactions for the molecules absorbed on noble metal nanostructures hold potential for sensitive optical sensors [1-3]. For example, anomalously high Raman signals can involve chemical and electromagnetic effects [23-5]. The latter effect relies on the oscillations of surface electrons (plasmon) when noble metal nanostructures are excited by incident light of a specific wavelength. Apart from wavelength of the incident illumination, morphology, and packing and geometrical arrangement of nanostructures as well as substrates are critical factors [6-10]. The generation of electromagnetic field (near field) under illumination can be theoretically calculated by solving 3-D Maxwell equations using discrete dipole approximation (DDA), finite difference time domain (FDTD), discontinuous Galerkin time domain (DGTD), and finite element method (FEM) [11]. Among these, discrete dipole scattering (DDSCAT) based on DDA is widely used due to its simplicity and ability for solving complex and irregular targets [12,13]. Of particular interest is a combination of experimental and theoretical approaches that could allow for discovery of unique nanoscale plasmonic architectures. Here, we report growth and plasmonic modeling of silicon nanowires (SiNWs), SiNWs decora