Two-dimensional Si_xGe_1-x films with variable composition made via multilayer colloidal template-guided ionic liquid electrodeposition

The binary alloy system Si_xGe_1-x provides a continuous series of materials with gradually varying properties. In this paper, we report on a fundamental basis a method to make large-area macroporous Si_xGe_1-x films with variable Ge content by electrodeposition in an ionic liquid, with SiCl₄ and GeCl₄ as precursors. The chemical composition of the products can be modified by changing the molar ratio of the precursors. Periodical macroporous Si_xGe_1-x was made by a multilayer polystyrene (PS) template assembled as face-centered cubic lattice. Two-dimensional (2-D) Si_xGe_1-x bowl-like and fishing-net structures can be obtained by applying different deposition temperatures. The results highlight the potential applications, including photonic bandgap and battery materials, as well as ultra-thin gratings, due to the effect of modification of light and improved tunability of composition, although Si_xGe_1-x made by our method is sensitive to oxidation by air.