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

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 T_fs from 1150 to 1950 °C. It was found that the morphologies of these nanowires were strongly dependent on the T_f attributed to the different decomposition reactions of SiH₄ and CH₄ molecules in the range of T_f. The hydrogen-assisted heat transfer effect induced the growth of the single-crystalline NiSi core, the polycrystalline Si, and amorphous SiC shells at T_f 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.