Silicon Nanowires Growth Via Plasma Assisted Vapor-liquid-solid Technique

Résumé: Silicon nanowires (SiNWs) have received considerable attention as base materials for third-generation photovoltaic devices because they lend themselves to large- scale production with enhanced light trapping and increased overall performance. As the properties of tin and indium, nanoparticles govern the properties of the SiNWs. This thesis investigates their formation and properties by depositing Sn and In layers on various substrates. The work was divided into two part; first, we studied the SiNWs grown on p-type boron-doped (100) oriented silicon wafers (c-Si) as well as on hydrogenated amorphous silicon (a-Si:H), hydrogenated amorphous silicon carbon (a-SiC:H), and hydrogenated amorphous silicon-germanium (a-SiGe:H) coated c-Si substrates. Sn and In-assisted SiNWs have been grown on different substrates coated 1 nm of Sn and In via plasma enhanced chemical vapor deposition (PECVD) via the Vapor-Liquid-Solid technique to study the impact of the substrate surface energy and catalyst type on the morphology, the structure and optical properties of the synthesized SiNWs. The second part is devoted to the SiNWs deposited on Corning glass (Cg), a-Si:H/Cg and a-SiC:H/Cg substrates. Sn-and In-SiNWs on a-Si:H/Cg and a-SiC:H/Cg substrates confirm the change of SiNWs properties by changing metal and substrate nature and show inhomogeneous distribution in diameters and very little density. The suppression of SiNWs growth showed the failure of 1D growth resulting from high temperature growth during the PECVD process. Important results were observed at a catalyst thickness of 50 nm for Sn and In-assisted SiNWs on Cg the 1TO Raman peak was closest to the crystalline Si peak location. The absence of an amorphous component at 480 cm-1 may be caused by the presence of thicker metal (50 nm), which causes the samples to completely crystallize. The optical reflectance from SiNWs grown on various substrates coated Cg is lower than that from SiNWs grown on the substrates coated p-type boron-doped (100) oriented c-Si substrate.

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