Two-dimensional nanoplates of Bi2Te3 and Bi2Se3 with reduced thermal stability

Abstract

Free-standing thin nanoplates of Bi2Te3 and Bi2Se3 were synthesized by solvothermal method. It was demonstrated that the thickness of the nanoplates can be controlled by introducing a controlled amount of polyvinylpyrrolidone (PVP) in the synthesis reaction. PVP bonds to the polar basal planes of hexagonal crystal structure of Bi2Te3 and Bi2Se3, and they suppress the growth (speed) of the hexagonal crystals in the c-axis direction. Highly anisotropic growth yielded the formation of 2-dimensional nanostructures of nanoplates. The plates were examined directly with transmission electron microscopy (TEM) with in-situ heating. These crystalline nanoplates with extremely high width to thickness ratios were found to exhibit much lower thermal stability compared to the bulk counterpart or the conventional nanoparticles as represented by the reduced melting temperature. The melting temperature of a nanoplate decreased by more than 100°C compared to the melting temperature of the bulk material. While it is widely known that the meting temperature decreases for nanoparticles with reduced sizees in all three spatial dimensions, we demonstrate that the reduction in one dimension, i.e. thickness of the platelets in the present study, is effective enough to induce much greater decrease of the melting point than the decrease as observed for the case of nanoparticles.

Temperature-Dependent Raman Scattering of Large Size Hexagonal Bi2Se3 Single-Crystal Nanoplates

“…With a band gap of 0.3 eV, Bi 2 Se 3 is the most important V-VI semiconductor [20][21][22][23]. Bi 2 Se 3 has an extensive application as thermoelectric and photoelectric materials near the room temperature [24,25]. Raman spectroscopy was an important tool to characterize the physical properties of various nanostructures, such as: 1T-TaS 2 [26], TiS 3 [27], MoS 2 [28], CoFe 2 O 4 [29], CuGaO 2 [30], Bi 3.25 La 0.75 Ti 3 O 12 [31], ZnSe [18,32], ZnO [33], etc.…”

TEM Nanosculpting of Topological Insulator Bi$_2$Se$_3$

“…5 Tuning the thickness of nanostructures may also permit control over transport phenomena. 6,7 Implementing these ideas is challenging, however, because most growth methods yield nanostructures in a great variety of sizes and shapes during the same process. This limits the ability to build devices to exact specifications and furthermore limits future scalability of geometrydependent devices.…”

Transmission Electron Microscope Nanosculpting of Topological Insulator Bismuth Selenide

“…7−9 Tuning the thickness of nanostructures may also permit control over transport phenomena. 10,11 Implementing these ideas is challenging, however, because most growth methods yield nanostructures in a great variety of sizes and shapes within the same process. This limits the ability to build devices to exact specifications and furthermore limits future scalability of geometry-dependent devices.…”

“…This occurs with large surface-to-volume ratio, so nanostructures of Bi 2 Se 3 are of particular interest. , In addition, theoretical proposals have suggested that specific nanostructure geometries may be able to enhance the material properties of Bi 2 Se 3 in useful ways. For example, patterning an antidot lattice into Bi 2 Se 3 may greatly improve its thermoelectric figure of merit; , Bi 2 Se 3 wires could be used as efficient interconnects in integrated circuits; and creating Bi 2 Se 3 wires and rings, and possibly pairing them with a superconductor, may allow for control of Majorana fermions and other topological phenomena, potentially assisting in fault-tolerant quantum computing. − Tuning the thickness of nanostructures may also permit control over transport phenomena. , Implementing these ideas is challenging, however, because most growth methods yield nanostructures in a great variety of sizes and shapes within the same process. This limits the ability to build devices to exact specifications and furthermore limits future scalability of geometry-dependent devices.…”