Growth of Si-based core–shell nanowires through gases decomposition reactions with tunable morphologies, compositions, and electrochemical properties

Abstract

Si-based core–shell nanowires grown on Ni-coated c-Si, glass and Ni foil substrates by hot-wire chemical vapor deposition were extensively investigated. The nanowires, which included NiSi nanowires, NiSi/Si core–shell nanowires, and NiSi/SiC core–shell nanowires, were grown by varying the Tfs from 1150 to 1950 °C. It was found that the morphologies of these nanowires were strongly dependent on the Tf attributed to the different decomposition reactions of SiH4 and CH4 molecules in the range of Tf. The hydrogen-assisted heat transfer effect induced the growth of the single-crystalline NiSi core, the polycrystalline Si, and amorphous SiC shells at Tf within the 1450–1650 and 1650–1950 °C ranges, respectively. The NiSi/Si core–shell nanowires demonstrated a relatively better electrochemical performance compared to the NiSi/SiC core–shell and NiSi nanowires with the specific capacity of 326 mF/cm2. The NiSi/Si core–shell nanowires exhibited good electrochemical stability at high current density with 61% capacity retention after 2000 cycles. The nucleation limited silicide reactions of the Si-based core–shell nanowires and the effects of the gas-phase reactions on the growth of the nanowires are discussed.