Anisotropic Growth of Cubic PbTe Nanoparticles to Nanosheets: Controlled Synthesis and Growth Mechanisms

Fabricating topologically anisotropic nanostructures of a cubic structured material may shed important light on the growth mechanisms that are crucial for fabricating self-assembled nanodevices. PbTe is a cubic structured narrow gap semiconductor that is technically important for thermoelectric energy conversion and infrared devices. We herein report the alkaline hydrothermal synthesis of PbTe single crystal nanosheets of 20−80 nm thickness and 0.2−5 μm length along the edge. The reaction parameters such time, temperature, NaOH concentration, type of surfactants and reductant have been systematically varied in order to establish the correlation between the recipe and the micromorphology of the final products. The time-dependent experiments suggest that the formation of PbTe nanosheets involves the spontaneous arrangement and alignment of PbTe nanoparticles via an oriented attachment process, and finally they form a single crystal upon fusion of the nanoparticles. The possible reasons for self-assembly of PbTe nanoparticles have been discussed. We also measured the Seebeck coefficient on a thin film sample made of these nanosheets, which reached the highest value of 120 μV·K −1 at 650 K.