Supercooling of Nanoscale Ga Drops With Controlled Impurity Levels

We use in situ observations by variable temperature transmission electron microscopy on Ga drops at the tips of GaAs nanowires to investigate the phase behavior of nanoscale Ga. Experiments on pure Ga drops are compared with drops containing well-defined levels of impurities. Our controlled experiments show that the crystallization temperature, and hence the ultimate achievable supercooling, strongly depends on the concentration of impurities. All drops show predominant \ensuremath{\beta}- and \ensuremath{\gamma}-Ga correlations in the liquid phase and ultimately crystallize to solid \ensuremath{\beta}- and \ensuremath{\gamma}-Ga, which provides support for a scenario in which impurities limit the achievable supercooling without significantly templating the crystalline phase.