Te-seeded growth of few-quintuple layer Bi₂Te₃ nanoplates

We report on a Te-seeded epitaxial growth of ultrathin Bi₂Te₃ nanoplates (down to three quintuple layers (QL)) with large planar sizes (up to tens of micrometers) through vapor transport. Optical contrast has been systematically investigated for the as-grown Bi₂Te₃ nanoplates on the SiO₂/Si substrates, experimentally and computationally. The high and distinct optical contrast provides a fast and convenient method for the thickness determination of few-QL Bi₂Te₃ nanoplates. By aberration-corrected scanning transmission electron microscopy, a hexagonal crystalline structure has been identified for the Te seeds, which form naturally during the growth process and initiate an epitaxial growth of the rhombohedralstructured Bi₂Te₃ nanoplates. The epitaxial relationship between Te and Bi₂Te₃ is identified to be perfect along both in-plane and out-of-plane directions of the layered nanoplate. Similar growth mechanism might be expected for other bismuth chalcogenide layered materials.