Raman and EPR Characterization of Diluted Magnetic Semiconductor Sb_2–xMn_xS₃ Nanocrystals Grown in a Glass Matrix

Abstract

Structural and magnetic property change for different Mn concentrations in diluted magnetic semiconductor Sb 2−x Mn x S 3 nanocrystals grown in a glass host matrix were investigated. Transmission electron microscopy images and energy dispersive X-ray analyses and Raman spectra with the modified model confirm the size and composition of nanocrystals. Electron paramagnetic resonance shows six hyperfine lines of the electron states, which are attributed to the interaction between the electron spin (S = 5/ 2) and the nuclear spin (I = 5/2) of Mn 2+ ions (3d 5 ) located in the crystal field of Sb 2 S 3 semiconductor. Also, a change in Mn−Mn interactions is observed as Mn concentration increases. The blueshift of the Raman band around 188 cm −1 with increasing Mn concentration gives strong indications of the substitution of Mn 2+ ions for Sb 3+ ions in the crystalline structure of Sb 2 S 3 . In addition, the band around 217 cm −1 remains constant for Mn concentrations of 0.00−0.10. However, for x = 0.20, a displacement of 210 cm −1 occurs, which indicates an interstitial incorporation of Mn ions in the Sb 2 S 3 structure at high Mn concentrations. A Raman high-frequency "shoulder" mode at 339 cm −1 is observed. Therefore, in this work, Sb 2−x Mn x S 3 nanocrystals were grown successfully.

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

“…Raman scattering is a fast and nondestructive technique to get insight into the electron–phonon interactions and the phonon dynamics in several materials, such as topological insulators [ 30 ] and, mainly, DMS NCs. [ 6 ] The vibrational modes of the DMS NC show changes with the concentration of TM‐ions, as reported for Sb 2 − x Mn x S 3 , [ 29 ] Bi 2 − x Cr x S 3 , [ 31 ] Cd 1 − x Mn x S, [ 6 ] Cd 1 − x Co x S, [ 32 ] and Zn 1 − x Mn x O NCs. [ 16,17 ] In this context, we reported the synthesis of DMS Bi 2 − x Mn x Te 3 NCs in a glass matrix and investigated them using transmission electron microscopy (TEM), Raman spectroscopy, and electron paramagnetic resonance (EPR).…”

“…The results give strong evidence of the incorporation of Mn 2+ ions in the atomic vacancies and interstices of the Bi 2 Te 3 NC structure due to the increase in atomic mass and consequently, a decrease in the wavenumber of the normal vibrational modes. [ 29,32,51 ] The band around 91.5 ± 0.5 cm −1 ( ) remains constant for the x = 0.00 and x = 0.05 concentrations and shows a redshift of ~0.5 cm −1 for the x = 0.10 to x = 0.20 concentrations. Although the variation is within the instrumentation precision limitation (~ 0.5 cm −1 ), this small change suggests that, in this mode, the doping Mn atom occupies the Bi vacancy (V Bi ) [ 51,63 ] along the monoatomic plane Te (1)–V Bi –Te (2)–Bi–Te (1), filling in the lattice defects to give rise to the new plane of atoms Te (1)–Mn–Te (2)–Bi–Te (1) in the QL.…”

“…As reported for nanostructure systems doped with Mn, the decrease in structural defects can be attributed to the ion diffusion process at 500°C. [ 6,17,29,31,32 ]…”

“…It is observed that with the increase of the xMn‐concentration, the σ size dispersion of the spherical NCs decreases as a consequence of the correction of point defects (vacancies) in the crystalline structure. [ 6,17,29,31,32 ] Thus, magnetic doping can be satisfactorily used to control and reduce the density of structural defects in Bi 2 – x Mn x Te 3 NC, improving their crystallographic quality and, consequently, the performance of the magneto‐optical device based on this type of NC. [ 6 ]…”

“…[ 20 ] As an example, the DMS NC is grown in a glass matrix that has optical and magnetic properties dependent on the concentration of transition metals, such as Bi 2 − x Mn x S 3 , [ 21 ] Bi 2 − x Co x S 3 , [ 22 ] Bi 2 − x Fe x S 3 , [ 23 ] Bi 2 − x Mn x Te 3 , [ 24 ] Bi 2 − x Cr x Te 3 , [ 25 ] Cd 1 − x Mn x S, [ 26 ] Pb 1 − x Mn x S, [ 27 ] Pb 1 − x Co x Se, [ 28 ] and Sb 2 − x Mn x S 3 . [ 29 ]…”