Morphology control of c-Si via facile copper-assisted chemical etching: Managements on etch end-points

摘要

Micro-ano-structures enable crystalline silicon (c-Si) to be prominent in many fields. In this work, an elaborate study on texturing c-Si via copper-assisted chemical etching (Cu-ACE) is reported. Various large-area craters arrays including gyro-like craters arrays, standard inverted pyramids arrays and deformed inverted pyramids arrays, together with mesoporous surfaces and polished-like surfaces are synthesized on Si wafers with Cu-ACE. An electrokinetic "H2O2 consumption" model and an energy band model are proposed to explain the synergetic effects between isotropic and anisotropic etching on preparing Si micro-ano-structures during etching. It is demonstrated that the etched morphology is determined by the temporal H2O2 relative concentration at etch end-points, which is accurately controlled by etching conditions. A "curved sidewalls" model is put forward, for the first time, to illustrate the nuances among etched craters arrays. Based on this model, the local H2O2 relative concentration determines local curvatures of sidewalls. Textured Si wafers with inverted pyramids arrays exhibit excellent anti-reflection abilities and are promising for solar cells, photodiodes or other optoelectronic applications. Notably, our work provides a facile and controllable approach to produce various Si micro-anostructures which are of practical values in many domains.