Experimental Details

Single-crystal squares 3-4 mm thick were cut from a 2.5 cm-diameter Cu(100) cylindrical ingot which had been aligned by Laue X-ray diffraction. The crystals were mechanically polished to a 0.1 pm diamond finish followed by electropolishing in 85 vol% phosphoric acid [3]. After extensive rinsing with water the substrate was transferred to the STM electrochemical cell and immersed in 10 mmol/1 HC1. A Digital Instruments Nanoscope m STM was used for these experiments. The electrochemical cell incorporated an Ag/AgCl or immersed copper wire "quasi" reference electrode, a platinum counter electrode and an insulated tungsten tunneling probe. The tungsten probes were prepared by etching a W wire to form a sharp tip in 1 mol/1 KOH. The etching parameters were 30 V a.c. (Variac) versus a carbon rod followed by a 15 second etch at 8-10 V a.c. The probes were then coated with polyethylene, which in the most favorable cases results in a background Faradaic current of less than 10 pA. Homoepitaxial deposition of copper was examined in a dilute, nominally ~1 mmol/1, cuprous chloride electrolyte while the preliminary investigation of nickel deposition was performed using a concentrated electrolyte of 1.5 mol/1 Ni(S03NH2)2 (Fluka), 0.5 mol/1 H3BO3, with a pH of 3.5.

0 0

Post a comment