Study of vibrational properties of Bi2 − xMnxTe3 nanocrystals in host glass: Effect of xMn‐concentration

• Published in: Journal of Raman spectroscopy 2022-01, Vol.53 (1), p.95-103
• Main Authors: Santos Silva, Alessandra, Guimarães, Éder Vinícius, Cano, Nilo Francisco, Silva, Ricardo Souza
• Format: Article
• Language: English
• Subjects: Bi2 − xMnxTe3 NCs; Bismuth tellurides; Crystals; Electron paramagnetic resonance; Electron spin resonance; Hyperfine structure; Image transmission; Lattice vibration; Magnetic properties; Magnetic semiconductors; Manganese ions; Mathematical analysis; Matrices (mathematics); Mn2+ ions; Nanocrystals; Optical properties; quantum size; Raman spectra; Raman spectroscopy; Size effects; Transmission electron microscopy; vibrational modes; Vibrations
• ISSN: 0377-0486; 1097-4555
• DOI: 10.1002/jrs.6255

The Raman and infrared (IR) active lattice vibrations of xMn‐concentration Bi2 − xMnxTe3 nanocrystals (NCs) as a dopant in semiconductor Bi2Te3 nanocrystals grown in a host glass matrix, whose symmetries correspond to the R3¯m−D3d5 space group, are investigated by Raman scattering. Transmission electron microscopy images confirm the formation of Bi2 − xMnxTe3 nanocrystals with an average size of around 5.4 nm. The observation of the six hyperfine structure lines in electron paramagnetic resonance spectra confirms the incorporation of Mn2+ ions in Bi2Te3 nanocrystals. The vibrational modes of quintuple layer (QL) of the diluted magnetic semiconductor Bi2 − xMnxTe3 nanocrystals are modified in relation to pure Bi2Te3 nanocrystals. The appearance of the A2u1 (95.5 cm−1), A2u2 (114 cm−1), and Eu2 (103 cm−1) IR‐active modes is mainly due to quantum size effects. Indeed, the redshifts of the A2u1 (95.5 cm−1), Eu2 (103 cm−1), Eg2 (110 cm−1), A2u2 (114 cm−1), and A1g2 (141 cm−1) vibrational modes give strong indications of the substitutional and interstitial incorporation of Mn2+ in the Bi2Te3 crystalline structure. In addition, the Raman spectra show the formation of Bi2OTe2 semiconductor due to the appearance of the (123 cm−1) mode. The investigation of the Bi2 − xMnxTe3 nanocrystal has promising potential to design new devices with magnetic and optical properties adjusted according to the xMn‐concentration. This study reports Raman spectroscopy, along with the transmission electron microscopy (TEM) and electron paramagnetic resonance (EPR) experimental techniques to analyze Bi2 − xMnxTe nanocrystals, aiming for technological applications. Raman spectroscopy is an optical technique that is highly sensitive to Mn‐incorporation and which can probe various physical and chemistry properties of dilute magnetic semiconductor (DMS) from the nanostructure's phonon spectrum changes.