中国科学院材料磨损与防护重点实验室/先进润滑与防护材料研究发展中心知识库

Porous silicon (PS) films with photocarrier-created pores (PCPs) in the films and symbiotic inverted pyramids (SIPs) at the interfaces were prepared by electrochemical etching of n-type silicon in HF ethanol solution. The effect of back side illumination, doping level of silicon, current density and HF concentration on pore and interface morphology of PS films were investigated. SEM results demonstrated that Photocarriers, generated by back side illumination, was essential to the formation of PCPs and SIPs. The moderately doped n-type silicon with P doping level in 1.1 × 10¹⁷−2 × 10¹⁶ was suitable for PCP formation. The sizes of SIPs and the quantity of PCPs at their centers could be adjusted by current density when it was smaller than 25 mA cm⁻², in which the formation of PCPs competed with the growth of PS film for photocarriers and the increase of current density enhanced the growth of PS film. The formation of SIPs with four crystal planes approaching energy-stable (111) planes was believed to balance these two competitive behaviors. Since the PCPs were actually caused by photocarrier-promoted chemical etching, the HF concentration suitable for PCP formation was smaller than 20%.