Epitaxial thin films of copper(I) oxide (Pn3m, a = 0.427 nm) were electrode
posited onto [110]-, [111]-, and [100]-oriented single-crystal copper (Fm3m
, a = 0.3615 nm) by reduction of copper(II) lactate in solution. Cu2O films
grown on Cu(110) and Cu(III) exhibited both an out-of- and in-plane orient
ation following that of the substrate as measured by 2 theta and azimuthal
X-ray scans, up to a thickness of 0.8 mum. X-ray diffraction studies showed
that Cu2O films deposited onto Cu(100) grow initially with a near-[III] or
ientation up to a critical thickness, beyond which film growth is primarily
in the [100] direction. The films were found to be both in- and out-of-pla
ne oriented throughout, as measured by azimuthal X-ray scans. In situ 2 the
ta X-ray measurements showed a critical thickness for growth in the [100] d
irection of about 360 nm. As determined from scanning electron microscopy i
mages, the Cu2O films deposited onto Cu(100) grew with triangular facets co
nsistent with the [III] orientation prior to the critical thickness, and th
en as pyramidal islands over the initial triangular layers above this thick
ness. A proposed interface model of Cu2O(III) over Cu(100) yields a low mis
match and a high number of atomic contact points per unit area, offering a
possible explanation for the initial [III]-oriented deposition.