  Interfacial bond formation during sputter deposition of metal oxide thin
films onto polycarbonate (PC) is investigated by ab initio molecular dynamics
simulations and X-ray photoelectron spectroscopy (XPS) analysis of PC | X
interfaces (X = Al$_2$O$_3$, TiO$_2$, TiAlO$_2$). Generally, the predicted bond
formation is consistent with the experimental data. For all three interfaces,
the majority of bonds identified by XPS are (C-O)-metal bonds, whereas C-metal
bonds are the minority. Compared to the PC | Al$_2$O$_3$ interface, the PC |
TiO$_2$ and PC | TiAlO$_2$ interfaces exhibit a reduction in the measured
interfacial bond density by ~ 75 and ~ 65%, respectively. Multiplying the
predicted bond strength with the corresponding experimentally determined
interfacial bond density shows that Al$_2$O$_3$ exhibits the strongest
interface with PC, while TiO$_2$ and TiAlO$_2$ exhibit ~ 70 and ~ 60% weaker
interfaces, respectively. This can be understood by considering the complex
interplay between the metal oxide composition, the bond strength as well as the
population of bonds that are formed across the interface.
