Transmission electron microscopy study of Pb-depleted disks in PbTe-based alloys.

Even though the crystal structure of lead telluride (PbTe) has been extensively studied for many years, we discovered that the structure has a strong tendency to form Pb-depleted disks on {001} planes. These disks are around 2-5 nm in diameter and less than 0.5 nm in thickness, with a volume density of around 9 x 10¹⁷ cm^-3, resulting in lattice strain fields (3-20 nm) on both sides of the disks along their normal directions. Moreover, such disks were also observed in Pb-rich Pb_1.3Te, Pb-deficient PbTe_1.3, and thallium (Tl)-doped Tl_0.01Pb_0.99Te and Tl_0.02Pb_0.98Te crystals. Because of the effects of diffraction contrast imaging by transmission electron microscopy and orientations of the crystals, these native lattice strain fields were incorrectly recognized as precipitates or nanoinclusions in PbTe-based materials. This discovery provides new insight into the formation mechanism of the precipitates or nanoinclusions in PbTe-based materials. [ABSTRACT FROM AUTHOR]