RF plasma treatment of porous silicon

Abstract

The effect of oxygen and hydrogen rf plasmas on the photoluminescence (PL) spectra of porous silicon (PS) was studied. PS samples were prepared from p-type, (100) oriented silicon wafers with a resistivity of 0.03 Ω cm by electrochemical anodization in an ethanol-containing solution. The plasma treatments were carried out in a planar reactor for 150 min, whereas the samples were placed on the ground electrode and heated to 250°C. The PL was excited by the 548 nm line of Hg lamp and measured using a monochromator and lock-in amplifier. Both hydrogen and oxygen plasma treatments led to a decrease in PL intensity. The decrease was with a factor of 5 after hydrogen and 2.5 after oxygen plasma treatment. It was established by means of Auger electron spectroscopy (AES) that both plasma treatments led to an increase in the oxygen content and to a decrease in the carbon content on the PS surface. However, no direct correlation between the AES data and the PL intensity could be established. We suggest that the appearance of plasma-induced electronic defects, rather than the change in the surface chemistry, accounts for the PL quenching.