Electrosynthesis of Cobalt Telluride Thin Films by Voltammetry Combined with Electrochemical Quartz Crystal Microgravimetry

Cobalt telluride (CoTe) thin films were electrodeposited for the first time using alkaline solutions containing nitrilotriacetic acid (NTA), CoCl 2 , and K 2 TeO 3 . NTA was employed in order to shift the reduction potential of cobalt in the negative direction and to stabilize Co 2+ ions in alkaline electrolytes via the formation of Co-NTA complexes. The electrodeposition mechanism was investigated by linear sweep voltammetry (LSV) combined with electrochemical quartz crystal microgravimetry (EQCM). The formation of CoTe is proposed to occur through the reaction of Co 2+ with HTe − , which is generated by the reduction of TeO 3 2− via a 6-electron reduction pathway. A concurrent pathway consists of the stepwise reduction of TeO 3 2− to Te by a 4-electron process, followed by the 2-electron process reduction of Te to HTe − . The electrodeposited CoTe films were characterized by a variety of physical methods including scanning electron microscopy, energy dispersive X-ray, X-ray diffraction, and X-ray photoelectron spectroscopy. An optical energy bandgap of ∼1.86 eV was obtained by diffuse reflectance spectroscopy.