  Electrical properties of metal-semiconductor (M/SC) and metal/oxide/SC
structures built with Zr or ZrO\_2 deposited on oxygen-terminated surfaces of
(001)-oriented diamond films, comprising a stack of lightly p-doped diamond on
a heavily doped layer itself homoepitaxially grown on a Ib substrate, are
investigated experimentally and compared to different models. In Schottky
barrier diodes, the interfacial oxide layer evidenced by high resolution
transmission electron microscopy and electron energy losses spectroscopy before
and after annealing, and barrier height inhomogeneities accounts for the
measured electrical characteristics until flat bands are reached, in accordance
with a model which generalizes that of R.T. Tung [Phys. Rev. B 45, 13509
(1992)] and permits to extract physically meaningful parameters of the three
kinds of interface: (a) unannealed ones; (b) annealed at 350{\textdegree}C; (c)
annealed at 450{\textdegree}C, with characteristic barrier heights of 2.2-2.5 V
in case (a) while as low as 0.96 V in case (c). Possible models of potential
barriers for several metals deposited on well defined oxygen-terminated diamond
surfaces are discussed and compared to experimental data. It is concluded that
interface dipoles of several kinds present at these compound interfaces and
their chemical evolution due to annealing are the suitable ingredients able to
account for the Mott-Schottky behavior when the effect of the metal work
function is ignored, and to justify the reverted slope observed regarding metal
work function, in contrast to the trend always reported for all other
metal-semiconductor interfaces.
