  Ultra-wide bandgap and the absence of shallow dopants are the major
challenges in realizing diamond based electronics. However, the surface
functionalization offers an excellent alternative to tune electronic structure
of diamonds. Herein, we report on tuning the surface electronic properties of
hydrogenated polycrystalline diamond films through oxygen functionalization.
The hydrogenated diamond (HD) surface transforms from hydrophobic to
hydrophilic nature and the sheet resistance increases from ~ 8 kohms/sq. to
over 10 Gohms/sq. with progressive ozonation. The conductive atomic force
microscopic (c-AFM) studies reveal preferential higher current conduction on
selective grain interiors (GIs) than that of grain boundaries confirming the
surface charge transfer doping on these HDs. In addition, the local current
conduction is also found to be much higher on (111) planes as compared to (100)
planes on pristine and marginally O-terminated HD. However, there is no current
flow on the fully O-terminated diamond (OD) surface. Further, X-ray
photoelectron spectroscopic (XPS) studies reveal a redshift in binding energy
(BE) of C1s on pristine and marginally O-terminated HD surfaces indicating
surface band bending whilst the BE shifts to higher energy for OD. Moreover,
XPS analysis also corroborate c-AFM study for the possible charge transfer
doping mechanism on the diamond films which results in high current conduction
on GIs of pristine and partially O-terminated HDs.
