Secondary phase Cu2SnSe3 vs. kesterite Cu2ZnSnSe4: similarities and differences in lattice vibration modes

TL;DR

This study uses first-principles calculations to compare lattice vibration modes of Cu2SnSe3 and Cu2ZnSnSe4, identifying unique phonon signatures and structural features that distinguish these two similar semiconductors.

Contribution

It provides a detailed lattice-dynamical comparison of Cu2SnSe3 and Cu2ZnSnSe4, highlighting structural motifs influencing their vibrational properties.

Findings

Identification of vibration modes as fingerprints for material discrimination

Emphasis on structural motifs like chains and stripes affecting phonon modes

Good agreement of optimized structure with experimental data

Abstract

The crystal structure of monoclinic semiconductor Cu2SnSe3 is optimized, in a first-principles LDA calculation by Siesta method, to be found in good agreement with available experimental data, on which base zone-center transversal phonon modes are further calculated. The comparison with a similar calculation for kesterite-phase Cu2ZnSnSe4 helps to identify vibration modes promising to serve as fingerprints for discrimination of these two materials from their lattice-dynamical properties. Moreover, a full analysis of vibration modes is done, which emphasizes an importance of structural motives present in Cu2SnSe3 but absent in kesterite, namely continuous planar chains and stripes of like cations/anions, for the manifestation of structure-specific vibration lines.