N. Jedrecy et al., Copper growth on the O-terminated ZnO(000(1)over-bar) surface: Structure and morphology - art. no. 085424, PHYS REV B, 6408(8), 2001, pp. 5424
The effects of copper deposition or). the ZnO(000 (1) over bar) O-terminate
d surface at 300 K have been studied by surface x-ray diffraction (SXRD). T
erraces about 550 Angstrom wide, presenting a (1 x 1) bulk-derived order, w
ere obtained on the clean surface after repeated cycles of Ar+ sputtering-a
nnealing. The SXRD data show that inward relaxation takes place in the two
topmost planes (-0.2 Angstrom for the first O plane) while the site occupan
cy in the second Zn plane is reduced by one quarter. Upon copper adsorption
, a full derelaxation of the O surface is observed. In addition, the ordere
d fraction of atoms in the top O plane is reduced by one quarter, a feature
that may be associated to some O-Cu interaction. The Cu adatoms involved i
n such interaction could be responsible for the surface derelaxation throug
h a charge transfer, No change is detected concerning the CuZnO(000 (1) ove
r bar)-(1 x 1) surface up to an equivalent of several monolayers of deposit
ed copper. Copper aggregates into flat islands, with two orientational rela
tionships, at 180 degrees from each other: Cu(111)//ZnO(000 (1) over bar) w
ith Cu[(1) over bar 10]//ZnO[100]. The islands are not strained on the subs
trate, even at very early stages of growth. The rodlike signal from the (11
1) facet is already measured for an equivalent of 5 Cu ML. The lateral grow
th proceeds preferentially along the ZnO[210] axis. Additional diffraction
signals, attributed to copper islands nucleating at the ZnO bilayer step ed
ges, are detected.