Electrochemical growth of copper on well-defined n-Si(1 1 1):H surfaces

Monohydride-terminated n-Si(1 1 1) electrodes were used as substrates for the electrodeposition of Cu from 0.1 M H2SO4 + 0.1 mM CuSO4. In situ scanning tunneling microscopy, ex situ atomic force microscopy and scanning electron microscopy revealed that (a) the nucleation starts preferentially at surface defects such as etch pits or step edges, and (b) the deposition occurs by a Volmer–Weber growth mode. In situ surface X-ray diffraction on this system, reported for the first time, revealed the structure and the epitaxial relationship of the copper deposit on the Si substrate. Under the X-ray beam, the Cu deposit could be stabilized only with a significant overpotential. Cu clusters grow with the (1 1 1), (1 1 0), and (0 0 1) planes oriented parallel to the Si(1 1 1), with the first two orientations being dominant. Within the Si(1 1 1) plane, Cu clusters can be found in any rotational orientation around the Si(1 1 1) surface normal. The intensity distribution can be described as powder rings. This distribution is, however, peaked along specific directions. For the Cu clusters with Cu(1 1 0)∥Si(1 1 1) it is found that in-plane Cu〈1 1 1〉∥Si〈1 1 0〉. The peaks in the distribution of the Cu clusters with Cu(1 1 1)∥Si(1 1 1) reveal that these Cu clusters are basically rotated by 30° around the Si(1 1 1) surface normal but exhibit additionally a ±4.5° epitaxial rotation around the mean, high symmetry direction.