Ion-Induced Surface Reactions and Deposition of Trimethyl(methylcyclopentadienyl)platinum(IV)

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.