Silicon microcolumn arrays grown by nanosecond pulsed-excimer laser irradiation

TLDR

Arrays of high aspect ratio silicon microcolumns are formed by cumulative nanosecond pulsed‑excimer laser irradiation, with growth strongly enhanced in oxygen‑containing atmospheres and conceptually similar to vapor–liquid–solid whisker growth. The study proposes that microcolumn growth results from pulsed‑laser melting of column tips combined with silicon deposition from vapor produced by ablation. The process relies on pulsed‑laser melting of column tips, which act as preferred deposition sites for silicon vapor, yielding a high axial growth rate.

Abstract

Arrays of high aspect ratio silicon microcolumns that protrude well above the initial surface have been formed by cumulative nanosecond pulsed-excimer laser irradiation of silicon. Microcolumn growth is strongly affected by the gas environment, being enhanced in air or other oxygen-containing ambient. It is proposed that microcolumn growth occurs through a combination of pulsed-laser melting of the tips of the columns and deposition of silicon from the intense flux of silicon-rich vapor produced by ablation of the surface regions between columns. The molten tips of the columns are strongly preferred sites for deposition, resulting in a very high axial growth rate. The growth process is conceptually similar to the vapor–liquid–solid method used to grow silicon whiskers. However, in the present case the pulsed-laser radiation fulfills two roles almost simultaneously, viz., providing the flux of silicon-containing molecules and melting the tips of the columns.