La1-xBi1+xS3 (x~0.08): An n-Type Semiconductor

TL;DR

This study reports the synthesis, structural characterization, and electronic properties of a new n-type bismuth chalcogenide semiconductor, La0.92Bi1.08S3, with potential applications in thermoelectrics.

Contribution

It introduces a novel bismuth sulfide compound with detailed structural, optical, and electronic characterization, expanding the family of bismuth-based semiconductors.

Findings

Crystallizes in monoclinic space group C2/m.

Exhibits a ~1 eV band gap and n-type conduction.

No phase transitions observed from 2 to 300 K.

Abstract

The new bismuth chalcogenide La0.92Bi1.08S3 crystallizes in the monoclinic space group C2/m with a = 28.0447(19) {\AA}, b = 4.0722(2) {\AA}, c = 14.7350(9) {\AA}, and $\beta$ = 118.493(5){\deg}. The structure of La0.92Bi1.08S3 is built up of NaCl-type Bi2S5 blocks, and BiS4 and LaS5 infinitely long chains forming a compact three-dimensional framework with parallel tunnels. Optical spectroscopy and resistivity measurements reveal a semiconducting behavior with a band gap of ~ 1 eV and activation energy for transport of 0.36(1) eV. Thermopower measurements suggest the majority carriers of La0.92Bi1.08S3 are electrons. Heat capacity measurements indicate no phase transitions from 2 to 300 K. Band structure calculations at the density functional theory level confirm the semiconducting nature and the indirect gap of La0.92Bi1.08S3.