Using galvanostatic electroforming of Bi 1– x Sb x nanowires to control composition, crystallinity, and orientation

Using galvanostatic pulse deposition, we studied the factors influencing the quality of electroformed Bi 1– x Sb x nanowires with respect to composition, crystallinity, and preferred orientation for high thermoelectric performance. Two nonaqueous baths with different Sb salts were investigated. The Sb salts used played a major role in both crystalline quality and preferred orientations. Nanowire arrays electroformed using an SbI 3 -based chemistry were polycrystalline with no preferred orientation, whereas arrays electroformed from an SbCl 3 -based chemistry were strongly crystallographically textured with the desired trigonal orientation for optimal thermoelectric performance. From the SbCl 3 bath, the electroformed nanowire arrays were optimized to have nanocompositional uniformity, with a nearly constant composition along the nanowire length. Nanowires harvested from the center of the array had an average composition of Bi 0.75 Sb 0.25 . However, the nanowire compositions were slightly enriched in Sb in a small region near the edges of the array, with the composition approaching Bi 0.70 Sb 0.30 .