Nucleation and solidification of laterally grown silicon micro-films on amorphous substrates using the VLS mechanism

• We created a new structure for observing silicon crystallite nucleation.
• Using a vapor–liquid–solid technique we were able to control nucleation silicon crystallites and grow them laterally.
• Statistical information on crystallite growth was gathered and growth rates determined.
• Differences in growth rates were explained through different undercooling experienced by gold–silicon liquids due to the presence of chromium.
• It was observed that growth was surface reaction limited for the experimental conditions used.

A new technique for nucleating and observing silicon crystallites in confined geometries over amorphous substrates has been demonstrated using the vapor–liquid–solid (VLS) mechanism. Unlike the originally proposed VLS nanowire growth mechanism on a silicon substrate, confined growth within amorphous structures does not have an available source of silicon to saturate the catalyst prior to deposition or to control crystal orientation during growth. Silicon crystallites were nucleated in confined geometries of amorphous materials at 450 °C, with a silane partial pressure of 46 mTorr and a growth time of 60 min. Crystallites with planar areas upwards of 17 µm2 were grown. It was found that there were two distinct solid lamellar morphologies present in the various test structures and that these morphologies affected the calculated growth rates, volumetric distributions and morphologies of the nucleated crystallites. The distribution of crystallite volumes for the two populations was measured and average growth rates were found between 3.17×10−2 µm3/(minute×µm2) and 2.30×10−2 µm3/(minute×µm2), where the area in the denominator represents the initial gold–vapor interface area. It is believed that the different gold–silicon lamellar morphologies can be attributed to residue of the chromium adhesion layer which increased the lamellar spacing due to decreased undercooling of the liquid gold–silicon solution. Undercooling was estimated to be 130 °C from the eutectic temperature in the samples believed to have had their chromium adhesion layers completely removed.