Removal of Ag remanence and improvement in structural attributes of silicon nanowires array via sintering

Metal-assisted chemical etching (MACE) is popular due to the large-area fabrication of silicon nanowires (SiNWs) exhibiting a high aspect ratio at a low cost. The remanence of metal, i.e., silver nanoparticles (AgNPs) used in the MACE, deteriorates the device (especially solar cell) performance by acting as a defect center. The superhydrophobic behavior of nanowires (NWs) array prohibits any liquid-based solution (i.e., thorough cleaning with HNO₃ solution) from removing the AgNPs. Thermal treatment of NWs is an alternative approach to reduce the Ag remanence. Sintering temperature variation is chosen between the melting temperature of bulk-Ag (962 °C) and bulk-Si (1412 °C) to reduce the Ag particles and improve the crystallinity of the NWs. The melting point of NWs decreases due to surface melting that restricts the sintering temperature to 1200 °C. The minimum sintering temperature is set to 1000 °C to eradicate the Ag remanence. The SEM-EDS analysis is carried out to quantify the reduction in Ag remanence in the sintered NWs array. The XRD analysis is performed to study the oxides (SiO and Ag₂O) formed in the NWs array due to the trace oxygen level in the furnace. The TG-DSC characterization is carried out to know the critical sintering temperature at which remanence of AgNPs removes without forming any oxides. The Raman analysis is studied to determine the crystallinity, strain, and size of Si nanocrystals (SiNCs) formed on the NWs surface due to sidewalls etching. An optimized polynomial equation is derived to find the SiNCs size for various sintering temperatures.