TEM observations of early nucleation and growth stages in aluminum films on liquid gallium droplets

Abstract

Transmission electron microscopy was used to study the early nucleation and growth stages of aluminum films grown on SiO film substrates covered with a thin (∼10 nm thick) layer of gallium. It was found that spherical aluminum crystals nucleate initially within the liquid gallium droplets and, as the deposition proceeds, they grow larger through a liquid metal mediated coalescence. An in-situ cooling experiment inside a transmission electron microscope has shown that the liquid gallium surrounding the solid aluminum crystals undergoes an anomalous supercooling behavior. At 86 K most of the gallium droplets had crystallized, but after warming to 207 K followed by cooling to 80 K, no solidification of gallium was observed again.