Journal of Electroanalytical Chemistry, Vol.614, No.1-2, 41-48, 2008
Electrochemical atom-by-atom growth of highly uniform thin sheets of thermoelectric bismuth telluride via the route of ECALE
Thermoelectric films of Bi2Te3 with highly uniform thin sheets structure were grown on Au substrate via the route of electrochemical atomic layer epitaxy (ECALE) in this work. Electrochemical aspects of Te and Bi on Au, Te on Bi-covered An, and Bi on Te-covered Au were characterized by means of cyclic voltammetry and coulometry. A steady ECALE deposition for Bi2Te3 compound could be attained after positively adjusting the underpotential deposition (UPD) potentials of Bi and Te on Au in steps over the initial 40 cycles, and the potentials could be kept constant for the following deposition. A 400-cycle deposit, which was grown with the steady deposition potentials, was proved to be a single phase Bi2Te3 Compound by X-ray diffraction (XRD) analysis. The 2:3 stoichiometric ratio of the deposit was further verified by energy dispersive X-ray (EDX) quantitative analysis. The band gap of the Bi2Te3 film was determined as 0.33 eV by Fourier transform infrared spectroscopy (FTIR) and blueshifted in comparison with that of the bulk Bi2Te3 single crystal. The field emission scanning electron microscope (FE-SEM) observation shows the deposit consisted of numberless interlaced thin sheets, which grown perpendicularly with the substrate. The formation mechanism of the morphology is investigated and it should be related to the property of the substrate and the lattice structure of Bi2Te3 compound. It is believed that the interlaced thin sheets structure may be profitable for the improvement of the thermoelectric properties. (c) 2007 Elsevier B.V. All rights reserved.
Keywords:electrochemical atomic layer epitaxy;underpotential deposition;Bi2Te3;thermoelectric materials;thin film