Passivation of Porous Silicon by LaF3 Using a Simple Single-Source Chemical Bath Technique

Passivation of porous silicon (PS) by LaF3 by a novel chemical-bath technique has been investigated in this report. The porous silicon surface has been passivated with LaF3 by reacting LaCl3 with HF in the etching chamber at room temperature. Without removing the porous silicon from the anodizing chamber LaF3 as a result of chemical reaction between LaCl3 and HF was allowed to passivate the PS surface. Several cycles of reaction that gives the various thickness of LaF3 layer on PS have been investigated. The Scanning Electron Microscopy (SEM) on the surface of LaF3/PS/Si structure confirms the LaF3 film deposition on PS layer. The X-ray diffraction (XRD) of the deposited layer revealed a hexagonal nanocrystalline LaF3 deposition. The as-deposited thin (10-cycle) LaF3 layer contained very low concentration of lanthanum (La) and fluorine (F). The concentration of La and F started increasing with the increase in reaction cycle. But the photoluminescence (PL) of as deposited-LaF3 passivated PS was lower than that of fresh PS. Annealing the just passivated PS structure recovered the PL intensity. Experimental results show that the optimized chemical bath passivation process for the LaF3 on porous silicon could enable the porous silicon to be an important material for photonic application.