EC-STM studies on copper electrodeposition at n-Si(1 1 1):H electrodes

In situ electrochemical-scanning tunneling microscope (EC-STM) was employed to investigate the electrodeposition of copper at the hydrogen-terminated n-Si(1 1 1) electrode in 3 mM CuSO4 + 0.1 M H2SO4 solution. Cyclic voltammogram at the silicon electrode showed a reduction peak of copper (II) at −1.2 V versus Cu(II)/Cu (−0.59 V versus SCE) without the corresponding anodic stripping peak at the scan rate of 50 mV/s, suggesting that a Schottky junction was formed when copper ions were deposited at the surface of n-Si(1 1 1):H by electroreduction. EC-STM images of the atomically flat n-Si(1 1 1):H revealed the step-edge deposition when copper was electrodeposited well before the peak potential, but the step-edge as well as terrace deposition after it. The difference in copper electrodeposition depending on the potential applied was corroborated by SEM images of the samples electrodeposited at the two experimental conditions for long time.