A Nonaqueous Way to Thermoelectric Nanowires

We present the electrochemical deposition of Bi₂S₃ and Pb_3xBi_2(1-x)S₃ into highly ordered porous alumina templates from organic electrolytes. These compounds and sulfosalts in general are semiconductors with a direct band gap transition. The band gap of the bulk Bi₂S₃-PbS alloys can be adjusted over a wide range from 0.25 eV up to 1.6 eV and exhibit a large variety of crystal phases. Those compounds are very suitable for the synthesis of crystallographically oriented 1D-nanostructures due to their modular crystallography. For the synthesis we dissolved 0.055 M (BiCl₃, PbCl₂) and 0.19 M elemental sulfur as precursors in dimethylsulfoxide (DMSO) as a nonaqueous solvent. The deposition took place under inert gas atmosphere at elevated temperatures (110degC). For the Bi₂S₃ we obtained nearly single crystalline nanowires and a homogenous pore filling up to membrane thickness of 30 mum. These nanowires exhibited a preferential orientation of the c-axis parallel to the nanowire axis. In case of lead dissolved in the structure in comparison to the corresponding crystal phase of the bulk material