Pressure dependent tailored attributes of silicon nanoneedles grown by VHF plasma technique

Abstract

Gold (Au) catalysts assisted well-aligned silicon nanoneedles (SiNNs) are synthesized using very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) method. The tailored morphology and the optical reflectance of such NNs are inspected as a function of varying reactor pressure (200-800 mTorr). FESEM images revealed the growth of high density SiNNs with diameter ranging from 45 to 600 nm and length as much as 5.66 ± 0.2 μm. Overall morphology of these NNs are found to be highly sensitive to the pressure variation, where appreciably aligned thinner NNs are achieved at 600 mTorr pressure. The presence of globule at the NNs tip authenticated their VLS mechanism mediated growth. The reactor pressure sensitivity of the aspect ratio, lattice parameters, Raman modes, and reflectance are demonstrated. XRD patterns manifested SiNNs cubic crystalline phase with preferred orientation along (111) direction. The occurrence of NNs high crystallinity is further supported by the Raman and HRTEM data. The reflectance of SiNNs grown at 600 mTorr exhibited remarkable reduction (∼6.3%) than those obtained at other pressures. This reactor pressure dependent significant modification in the physical properties of synthesized SiNNs may be prospective for the development of optoelectronics.