Improved structural features of Au-catalyzed silicon nanoneedles

Abstract

Nanometer sized silicon (Si) needles (nanowires) offer a vehicle for varieties of applications at nanoscale. We grow Si nanoneedles (SiNNs) using very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) method with distinct gold (Au) nanostructures (NSs) as catalyst. Au NSs in the form of nanoparticles (NPs) and continuous thin film are prepared on Si(1 0 0) substrates via radio frequency magnetron sputtering. Au catalyst size dependent surface morphology and structural features of these SiNNs are determined. Samples are characterized via imaging and spectroscopic measurements. Controlled growth of such SiNNs structure with reproducibility that is achieved via Au NPs size tunability is attributed to the vapor-liquid-solid (VLS) growth mechanism. SiNNs with diameters between 20 and 120 nm and length up to 5 µm are acquired. SiNNs diameter is found to increase with the increase of Au NPs size. Processing parameters optimization is demonstrated to play a critical role in nucleating Au NPs and thereby achieving high density SiNNs morphology. X-ray diffraction patterns authenticated an enhanced SiNNs crystallinity with increasing catalyst size. Raman spectra of SiNNs revealed a red-shift (~8.26 cm-1) in the first-order transversal band as the average diameter of NNs are decrease from 69 to 57 nm. Our systematic method for synthesis and characterization may contribute toward the development of SiNNs based optoelectronics.