In Vacuo XPS Study\non Pt Growth by Atomic Layer Deposition\nUsing MeCpPtMe<sub>3</sub> and N<sub>2</sub>/NH<sub>3</sub> Plasma

Atomic layer deposition (ALD) has been an attractive\ntool in the\nfabrication of Pt thin layers and nanoparticles. In this work, the\nsurface chemistry of Pt ALD through the MeCpPtMe<sub>3</sub>/N<sub>2</sub>-plasma (N<sub>2</sub>*) and the MeCpPtMe<sub>3</sub>/NH<sub>3</sub>-plasma (NH<sub>3</sub>*) processes at 300 °C have been\ninvestigated in detail using <i>in vacuo</i> X-ray photoelectron\nspectroscopy (XPS) during the ALD process, so that the evolution of\nsurface species at each step of the ALD cycle can be studied under\ngrowth relevant conditions. In particular, the nature of the N-containing\nsurface species and their role in the surface reactions during nucleation\nand steady growth are carefully scrutinized. Both processes are completely\nO-free. Persistent surface N and/or C species are detected, which\nare, however, not built into the film. Remarkably, the common N-species\nseen in other metal ALD processes by N-based plasmas, such as metal-NH<sub><i>x</i></sub> groups or N adatoms, are not present on\nthe growth surface. For the MeCpPtMe<sub>3</sub>/N<sub>2</sub>* process,\n−CN-H<sub><i>x</i></sub> is identified as the main\nN-containing species engaged in surface reactions. On the other hand,\nN-containing species seem to play an insignificant role in the NH<sub>3</sub>* process. It is revealed that the surface species and reaction\npathways of the MeCpPtMe<sub>3</sub>/N<sub>2</sub>* and the MeCpPtMe<sub>3</sub>/NH<sub>3</sub>* processes are not only different to those\nof the O-based processes but also differ from each other. On the basis\nof surface species quantification results, a growth mechanism is proposed\nfor the N<sub>2</sub>* and the NH<sub>3</sub>*-based processes, respectively.\nOur results show that N-based plasmas are a promising alternative\nto O-based reactants in Pt ALD growth.