Raman Spectroscopy of Two-Dimensional Bi2TexSe3 − x Platelets Produced by Solvothermal Method

Abstract

In this paper, we report a facile solvothermal method to produce both binary and ternary compounds of bismuth chalcogenides in the form of Bi2TexSe3 − x. The crystal morphology in terms of geometry and thickness as well as the stoichiometric ratio can be well controlled, which offers the opportunities to systematically investigate the relationship between microstructure and phonon scattering by Raman spectroscopy. Raman spectra of four compounds, i.e., Bi2Se3, Bi2Se2Te, Bi2SeTe2 and Bi2Te3, were collected at four different excitation photon energies (2.54, 2.41, 1.96, and 1.58 eV). It is found that the vibrational modes are shifted to higher frequency with more Se incorporation towards the replacement of Te. The dependence of Raman vibrational modes on excitation photon energy was investigated. As the excitation photon energy increases, three Raman vibrational modes (A1g1, Eg2 and A1g2) of the as-produced compounds move to low frequency. Three Infrared-active (IR-active) modes were observed in thin topological insulators (TIs) crystals.

Large-area epitaxial growth of MoSe2via an incandescent molybdenum source

“…All the observations described above are in good agreement with the reported Raman shift values of a previous study [13]. has not yet been identified but it is believed to come from a BiTeSe alloy thin layer at the interface between the Bi 2 Te 3 buffer and the MoSe 2 layer [14]. A wider spectral range covering Raman shifts from 100 to 1700 cm -1 was then used to study the spectra of the MoSe 2 thin films grown on HOPG and sapphire substrates and the resulted spectra are displayed as the top curves in Figure 4(c) and (d), respectively.…”

Ultra-broadband Nonlinear Saturable Absorption for Two-dimensional Bi2TexSe3−x Nanosheets

“…The thinner Bi 2 TeSe 2 nanosheet shows a greater sensitivity to the excitation intensity, which is consistent with the result above. However, it should be noted that this result cannot definitively confirm the role of the surface state in the nonlinear optical properties of the Bi 2 TeSe 2 nanosheet because it is still challenging to precisely control the crystal morphology in terms of geometry and thickness5. Although the thickness of the nanosheets is roughly controlled, its lateral size still varies from several hundred nanometres to several micrometres.…”

“…Further understandings about the Raman spectroscopy have been reported in our previous work, ref. 5. To further verify the crystal structure and phase of the Bi 2 Te x Se 3−x nanosheets, we performed an X-ray diffractometer (XRD) analysis on the four compounds, as shown in Fig.…”

“…5. Based on the solvothermal method, we produced high-quality Bi 2 Te x Se 3−x nanosheets with a regular hexagonal morphology and good crystallinity.…”

“…In recent years, significant efforts have been devoted to controlling the crystal morphology of TIs567, extending their applications in the electronics and optoelectronics fields8910, and improving their performance in thermoelectric devices1112.…”