Growth of Bimodal Sn-Catalyzed CdS Nanowires by Using Tin Sulfide

Sn-catalyzed CdS nanowires were grown by a physical vapor transport method by using tin sulfide as a precursor. The bimodal distribution consisting of tall/thin and short/thick nanowires is found at the growth temperatures of 250-350 degrees C. The tall/thin nanowires grow along 0001 while the short/thick nanowires grow along 0110 and all have wurtzite crystal structure. The relationships, valid in the wide range 25-150 nm in nanowire diameters, of d(c) = (2.64 +/- 0.08)dNw for the tall/thin nanowires and of d(c) = (1.27 +/- 0.02)d(Nw) for the short/thick nanowires, are obtained where d(c), and d(Nw) are the diameters of catalyst and nanowire, respectively. Using nucleation theory, we calculate that the energies of nucleation are quite similar for both types of nanowires, which may explain the bimodality. Both types of nanowires show prominent photoluminescence without any noticeable trace of impurity-related bands, indicating their high optical quality.