La(1-x)Bi(1+x)S3 (x ≈ 0.08): An n-Type Semiconductor.

The new bismuth chalcogenide La(0.92)Bi(1.08)S3 crystallizes in the monoclinic space group C2/m with a = 28.0447(19) Å, b = 4.0722(2) Å, c = 14.7350(9) Å, and β = 118.493(5)°. The structure of La(0.92)Bi(1.08)S3 is built 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 La(0.92)Bi(1.08)S3 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 La(0.92)Bi(1.08)S3.