Porous Silicon Formation by Metal-Assisted Chemical Etching

The method of metal-assisted chemical etching produces a porous silicon layer. Palladium particles are deposited on both: multi-crystalline and Czochralski grown mono-crystalline Si wafers by immersing them in $PdCl_{2}$ solution for 1 to 3 min. X-ray photoelectron spectroscopy analysis of Pd clusters shows a decrease in Pd metal fraction by prolonged immersion time t from $F_{Pd}$ = 71.2% for t = 1 min to $F_{Pd}$ = 61.4% for t = 3 min due to Pd oxidation process. Porous silicon forms by metal-assisted chemical etching in a HF:$H_{2}O_{2}$ solution for 1 to 3 min. Photoluminescence of metal-assisted chemical etched samples exhibits the peak with a maximum of t at λ=650 nm independent of the etching time. Simultaneously, the intensity of the photoluminescence spectra strongly decreases for extended etching time t = 3 min. This behavior is attributed to increasing layer macroporosity, which strongly reduces amount of light emitting nanocrystallites