Crystallization of PECVD grown Si nanowire and its characterization using confocal Raman and EELS studies

Abstract

In the present report, systematic studies on nanoclustered Au catalyzed vapour-liquid–solid growth of silicon nanowires (SiNWs) by plasma enhanced chemical vapour deposition (PECVD) technique are described. The growth of SiNWs is performed on not so conventional sapphire substrate as well as commonly used Si substrate. SiNWs grown on different substrates are characterized for their morphologies and structures. Field emission scanning electron microscopy analysis of grown SiNWs, having an average diameter of ~ 800 nm and a typical length of ~ 10 µm, shows a slight increase in density of nanowires grown on Si substrate when compared to that for the samples grown on sapphire without any morphological changes. Structural studies using high resolution transmission electron microscopy confirm the crystalline nature of SiNWs where the crystalline core with polycrystalline shell is encapsulated in the amorphous phase. Confocal Raman analysis, unambiguously, confirms the presence of amorphous silicon oxide and amorphous Si (a-Si) in the SiNWs. Electron energy loss spectroscopy for the Si L2,3 shows the presence of a-Si and SiO2 at the surface of nanowire affirming the encapsulation of SiNWs in amorphous phase. Annealing of the samples conducted at 900 °C for 15 min restores the crystalline nature within the SiNWs which is confirmed further from Raman analysis.