Gas phase generation and deposition of size-selected metal clusters

Abdela, Ahmed (2014). Gas phase generation and deposition of size-selected metal clusters. University of Birmingham. Ph.D.

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Abstract

This thesis presents modifications to and optimisations of a cluster beam source, one application being the generation of large area catalysis samples. A major modification to the cluster source also enabled coating of clusters in a new way. The impact of Pd $_5$ $_6$ $_1$ , Pd $_5$ $_5$ and Pd $_4$ clusters (1, 1.5 and 1 keV) on a thin material film evaporated onto a solid argon matrix led to deposition of large, 5-40 nm diameter, irregularly shaped particles. Furthermore, Pd $_9$ $_2$ $_3$ and Pd $_2$ $_0$ $_0$ $_0$ clusters, with both 0.5 and 1.5 keV impact energies, have been coated in-flight by impact on the thin film/solid matrix, as verified from the increase in diameters of the deposited particles and the detection of Pd signal by EELS.
MoS $_2$ nano pillar catalyst samples were etched using size-selected metal etch masks. Catalyst samples of ordered MoS $_2$ nano pillars were fabricated using NSL and a novel way to apply nano spheres was developed. Different etch recipes were used to obtain nano pillars with different diameters and heights; these recipes were also applied to reference MoS $_2$ samples without etch masks. Generally, the reference catalyst samples, with their roughened surfaces, showed higher HER activity than their corresponding ordered MoS2 nano pillar catalyst samples.