Silicon microcolumn arrays grown by nanosecond pulsed-excimer laser irradiation

Arrays of high aspect ratio silicon microcolumns that protrude well above t he initial surface have been formed by cumulative nanosecond pulsed-excimer laser irradiation of silicon. Microcolumn growth is strongly affected by t he gas environment, being enhanced in air or other oxygen-containing ambien t. It is proposed that microcolumn growth occurs through a combination of p ulsed-laser melting of the tips of the columns and deposition of silicon fr om the intense flux of silicon-rich vapor produced by ablation of the surfa ce regions between columns. The molten tips of the columns are strongly pre ferred sites for deposition, resulting in a very high axial growth rate. Th e growth process is conceptually similar to the vapor-liquid-solid method u sed to grow silicon whiskers. However, in the present case the pulsed-laser radiation fulfills two roles almost simultaneously, viz., providing the fl ux of silicon-containing molecules and melting the tips of the columns. (C) 1999 American Institute of Physics. [S0003-6951(99)04917-7].