FORMATION OF TILTED CLUSTERS IN THE ELECTROCHEMICAL DEPOSITION OF COPPER ON N-GAAS(001)

Using in-situ synchrotron X-ray diffraction, we have studied the epita xial properties of Cu clusters electrochemically deposited on n-GaAs(0 01) substrates. The Cu clusters have (001) base planes and their [100] directions are aligned with the [110] directions of the GaAs(001) sur face unit cell, but with a large angular spread of 4.5 degrees. Moreov er, the Cu(001) planes are tilted with respect to the GaAs(001) substr ate. The tilt of about 6 degrees did not show a preference for any sub strate azimuth, giving rise to a ring-shaped (111)(Cu) reflection. Thi s epitaxial tilt seems to be a novel mechanism of strain relief in an epitaxial system with a large mismatch of lattice constants and a larg e surface roughness.