Study of indium catalyst thickness effect on PECVD-grown silicon nanowires properties

Abstract

In this work, we focus on the elaboration at low temperature of metal-catalyzed silicon nanowires (SiNWs) obtained by vapor–liquid–solid (VLS) process. In particular, the effect of the metal thickness on SiNWs properties is reported. SiNWs are formed on indium (In) coated Si substrates using SiH4 as a precursor gas in plasma enhanced chemical vapor deposition (PECVD) reactor at a low substrate temperature of 400 °C. Morphological characterization has shown that increasing the thickness of indium layer leads to the increase of the (In) catalysts diameter, the SiNWs density, length and diameter. The grown SiNWs are randomly oriented and have a tapered form with an average length up to 7 µm for a deposition time of 15 min. According to X-ray diffraction patterns, SiNWs are highly crystalline with (111) (220) and (311) plane orientation. The Raman spectra show a downshift of the first-order optical phonon from 520 cm−1 for the c-Si to 517 and 513 cm−1 for SiNWs samples attributed essentially to the confinement effect in silicon nanowires. We notice also that SiNWs are composed essentially of amorphous and crystalline silicon. Increasing the indium thickness leads to the disappearance of the amorphous component and the presence of peaks assigned to nanocrystalline grains induced by the crystallization of the amorphous layer catalyzed by the indium particles.