Edge-induced flattening in the fabrication of ultrathin freestanding crystalline silicon sheets

摘要

Silicon nanomembranes are suspended single-crystal sheets of silicon, tens of nanometers thick, with areas in the thousands of square micrometers.Challenges in fabrication arise from buckling due to strains of over 10~(-3) in the silicon-on-insulator starting material.In equilibrium, the distortion is distributed across the entire membrane, minimizing the elastic energy with a large radius of curvature.We show that flat nanomembranes can be created using an elastically metastable configuration driven by the silicon-water surface energy.Membranes as thin as 6 nm are fabricated with vertical deviations below 10nm in a central 100μm×100μm area.