Temperature Dependence of Raman Spectra in Cu₂FeSnS₄ Magnetic Semiconductor Compound

Abstract

The temperature dependence of the Raman scattering by phonons performed in bulk polycrystalline Cu 2 FeSnS 4 , that crystallizes with tetragonal symmetry in space group P4, was measured between 10 and 300 K. The most important decay channel involves the three-phonon process with two phonons of the same branch, including combinations of optical phonons with equal or different frequencies. Additionally, coupling of an optical mode to two phonons of different branches is observed. The strong A-symmetry mode at 325 cm À1 decays into two optical phonons of the same frequencies v 1 ¼ v 2 % 162 cm À1 . To explain the change of Raman shift with temperature it is necessary to take into account the contribution of thermal expansion contribution. We have observed a soft mode in the Raman spectra which accounts for the antiferromagnetic phase transition that happens in this material at a N eel temperature of about 40 K. The full width at half maximum of this A-symmetry mode, extrapolated to zero temperature, is of about 2.6 cm À1 , when the contribution of intrinsic defect scattering, which is of about 3. cm À1 , is included in the calculation.

Anharmonic Effects in Ordered Kesterite-Type Cu2ZnSnS4

“…Interestingly, the four-phonon process was also shown to be the major decay mechanism for the isostructural kesterite-type Cu 2 ZnSnSe 4 thin films [45]. On the other hand, the thermal expansion term is the prevailing damping factor for the Raman-active phonons of the closely related stannite-type Cu 2 FeSnS 4 [46]. Since the latter sample was investigated in bulk form, as our Cu 2 ZnSnS 4 sample here, it appears that dimensionality strongly influences the exact phonon damping mechanism (at least within kesterite-type materials).…”

“…Literature data are also listed for comparison. The acronyms are explained as follows: CZSS, Cu 2 ZnSnS 4 ; TF, thin film; CZSS-TF1 [43], thin film grown on fluorinated tin oxide coated glass; CZSS-TF2 [44], thin film grown on soda lime glass; CZSSe-TF A [45], Cu 2 ZnSnSe 4 thin film, Zn-rich and Sn-poor, grown on Ta foil; CZSSe-TF B [45], Cu 2 ZnSnSe 4 thin film, Zn-poor and Sn-rich, grown on Ta foil; CFSS [46], Cu 2 FeSnS 4 (stannite structure); N/A, not available. We turn now to the modeling of the width Γ of the Cu 2 ZnSnS 4 A-bands as a function of temperature.…”

Retrieving Carrier Population and Collection Efficiency in CFTS/CFTSe‐Based Solar Cell Using Low‐Dimensional Multiple Nanostructures

“…These thin film materials have received limelight as they have many suitable properties such as direct bandgap in the range of 1-1.7 eV, high absorption coefficient (α > 10 4 cm À1 ), etc. [2][3][4][5][6][7][8] As the constituent of material is present in abundance and can be deposited with thin film layer, there is scope for reduction in the cost of solar cell. The achievable conversion efficiency of CZTS solar cell is just around 12.6% due to the presence of on-site defects with absorber.…”