Crystalline bismuth telluride nanoparticles grown by a magnetically assisted physical method

Abstract A magnetically assisted physical method was developed to synthesize crystalline bismuth telluride (Bi2Te3) nanoparticles. This method takes advantage of co-sputtering from Bi2Te3 and cobalt (Co) targets at elevated temperatures. Well-faceted polygonal or pyramidal nanoparticles were obtained from co-sputtering at a substrate temperature above 200 °C. The nanoparticles were analyzed to have a Bi to Te atomic ratio of 2 to 3, which represents the stoichiometric composition of Bi2Te3, without any detectable Co. The lateral size of Bi2Te3 nanoparticles generally increased in the range of 50–160 nm and their facet structure was better developed as the growth temperature increased. Electron microscopy studies revealed that the Bi2Te3 nanoparticles were distributed on the surface of a growing Bi2Te3 thin film. Both the nanoparticles and the thin film were proven to be highly crystalline by cross-sectional TEM and selected-area electron diffraction patterns. A series of physical mechanisms were proposed to account for this unique growth technique.