Three-Dimensional Bi2Te3 Nanocrystallites Embedded in 2D Bi2Te3 Films Grown by MOCVD

Two- (2D) and three-dimensional (3D) growth of nanostructured Bi2Te3 films was performed on 4° tilt (100) GaAs substrates using a metalorganic chemical vapor deposition system. To obtain 3D Bi2Te3 crystallites embedded in 2D planar film, we alternately changed the gas flow rate in the reactor. By repeating two steps, 3D Bi2Te3 crystallites embedded in 2D planar Bi2Te3 film were obtained. The thermoelectric properties in terms of the thermal conductivity, electrical conductivity, and Seebeck coefficient were investigated at room temperature. The thermal conductivities of the nanostructured Bi2Te3 films were from 0.63 W/(m K) to 0.94 W/(m K) at room temperature, which are low compared with that of film without nanostructure [1.62 W/(m K)]. The thermal conductivity of the film was effectively decreased with the decrease of size and increase of density of 3D crystallites. The results of this study open up a new method to fabricate nanostructured thermoelectric films with high thermoelectric figure of merit.