Electrodeposition of bismuth telluride from a weakly coordinating, non-aqueous solution

Abstract

We report the electrodeposition of bismuth telluride thin films on to titanium nitride (TiN) electrodes from a weakly coordinating solvent, dichloromethane (CH2Cl2), using the halometallates, [NnBu4][BiCl4] and [NnBu4]2[TeCl6] with 0.1M [NnBu4]Cl as the supporting electrolyte. The elemental composition of the electrodeposited films was found to be independent of the deposition potential between −0.6 and −2.0V vs. Ag/AgCl but to be dependent on ratio of the concentrations of the Bi and Te precursors in the solution, with the amount of bismuth in the films increasing when the concentration of [NnBu4][BiCl4] in solution was increased. All the electrodeposited films were found to be homogenous in composition across the electrode surface and to be reproducible in composition for replicate experiments. As the deposition potential was taken less negative, the morphology of the deposits changed from uniform films to films with a compact micro/nano particle structure as seen by scanning electron microscopy (SEM). Using this system, the electrodeposition of crystalline Bi2Te3 and Bi4Te3 was confirmed by energy dispersive spectroscopy (EDX) and grazing incidence X-ray diffraction.