Controllable Si (100) micro/nanostructures by chemical-etching-assisted femtosecond laser single-pulse irradiation

In this study, silicon micro/nanostructures of controlled size and shape are fabricated by chemicaletching- assisted femtosecond laser single-pulse irradiation, which is a flexible, high-throughput method. The pulse fluence is altered to create various laser printing patterns for the etching mask, resulting in the sequential evolution of three distinct surface micro/nanostructures, namely, ringlike microstructures, flat-top pillar microstructures, and spike nanostructures. The characterized diameter of micro/nanostructures reveals that they can be flexibly tuned from the micrometer (similar to 2 mu m) to nanometer (similar to 313 nm) scales by varying the laser pulse fluence in a wide range. Micro-Raman spectroscopy and transmission electron microscopy are utilized to demonstrate that the phase state changes from single-crystalline silicon (c-Si) to amorphous silicon (a-Si) after single-pulse femtosecond laser irradiation. This amorphous layer with a lower etching rate then acts as a mask in the wet etching process. Meanwhile, the on-the-fly punching technique enables the efficient fabrication of large-area patterned surfaces on the centimeter scale. This study presents a highly efficient method of controllably manufacturing silicon micro/nanostructures with different single-pulse patterns, which has promising applications in the photonic, solar cell, and sensors fields.