ABSTRACTThe selective formation of porous silicon in nanowires is observed in Si/Ge epitaxial layers along Ge layers grown by molecular beam epitaxy on a Si(100) substrate after metal-assisted chemical etching in aqueous HF-H2O2 solution. We assume that Ge layers serve as channels for a hole current out of the semiconductor to sustain the dissolution reaction. The tunnelling of holes through the potential barrier at the semiconductor surface is assumed to be the dominating mechanism of the hole transfer to the electrolyte.
Aligned and uniform silicon nanowires (SiNWs) arrays were fabricated with good controllability and reproducibility by metal-assisted chemical etching in aqueous AgNO3/HF etching solutions in atmosphere. The SiNWs formed on silicon were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), high-resolution transmission electron microscopy (HRTEM) and selected-area electron diffraction (SAED). The results show that the as-prepared SiNWs are perfectly single crystals and the axial orientation of the Si nanowires is identified to be parallel to the [111] direction, which is identical to the initial silicon wafer. In addition, a series of experiments were conducted to study the effects of etching conditions such as solution concentration, etching time, and etching temperature on SiNWs. And the optimal solution concentrations for SiNWs have been identified. The formation mechanism of silicon nanowires and silver dendrites were also discussed.
Study of Si Nanowires Produced by Metal-Assisted Chemical Etching as a Light-Trapping Material in n-type c-Si Solar Cells