화학공학소재연구정보센터
Journal of the Electrochemical Society, Vol.163, No.14, D801-D808, 2016
Electrodeposition of Dense Lead Telluride Thick Films in Alkaline Solutions
Dense PbTe thick films were electrodeposited in alkaline solutions by an underpotential deposition mechanism of Pb on overpotential deposited Te. The composition of Pb is critical for the material properties. The composition of the electrodeposited PbTe films was Te-rich. Although the applied potential had no substantial effect on the Pb composition, it needs to be in the proper range (from -0.8 to -1.1 V vs. sat. Ag/AgCl) to avoid further reduction of Te to Te-2(2-) or keep the reduction of Te to Te-2(2-) at a low reaction rate. To deposit dense thick films the pH must be maintained in the range 10.5 to 12.3. Higher TeO32- concentrations and lower pH values decreased the Pb composition but increased deposition rates. Varying the TeO32- concentration changed the surface morphology of thick PbTe films, but all the thick films were found to be dense in the SEM cross section images. The ratio of EDTA(4-)/Pb2+ is also a critical effect, and the data showed that 7.5 was the optimum ratio with the given conditions, where the electrodeposited PbTe film was dense without cracks. A high deposition rate (approx. 163 mu m/h) was achieved by high TeO32- concentrations (i.e., 550 mM) and at the deposition potential of 1.05 V vs sat. Ag/AgCl. The as-deposited PbTe films have relatively high Seebeck coefficient (i.e., 524 mu V/K), but low electrical conductivity compared to bulk counterpart which might be attributed to lower crystallinity of PbTe with embedded Te nanocrystals. (C) 2016 The Electrochemical Society. All rights reserved.