Ion-beam-induced
deposition using Me3PtCpMe has been
studied using a combination of ultrahigh vacuum (UHV) surface science
studies performed on thin films and scanning electron microscopy (SEM)
data of structures created under steady-state deposition conditions.
X-ray photoelectron spectroscopy (XPS) data from monolayer thick films
of Me3PtCpMe exposed to 1.2–4 keV Ar ions indicate
that deposition is initiated by energy transfer from the incident
ions to adsorbed precursor molecules leading to the loss of all four
methyl groups and the likely decomposition of the Cp ring, yielding
a deposit with a PtC5 stoichiometry. This contrasts with
focused electron-beam-induced processing (FEBIP), where deposition
occurs as a result of electron excitation and the loss of only one
Pt−CH3 group. By comparing the rate of Pt(IV) reduction
that accompanies either ion- or electron-induced decomposition of
Me3PtCpMe, it was determined that ion-induced deposition
reaction cross sections are approximately two orders of magnitude
greater. As a result of this higher reaction efficiency, ion irradiation
was accompanied by some bimolecular methyl radical coupling to produce
ethane. UHV studies also revealed that ion-induced deposition was
followed by sputtering of Pt and C atoms at comparable rates. These
fundamental insights provided by the UHV studies provided the basis
to understand SEM data obtained on structures that formed under steady-state
deposition conditions. In particular, the observation of “ring-like”
deposits could be rationalized by sputtering in the center of the
deposition region where the Ar+ flux was sufficiently high
to produce a precursor-limited regime, while deposition occurred in
ion-limited regimes at the periphery of the deposition region where
the Ar+ flux was lower. These results demonstrate the utility
of using data from a UHV surface science approach to better understand
the composition and influence of reaction conditions on deposits formed
during ion-beam-induced deposition of organometallic precursors.