Deposition of size-selected nanoclusters

Cao, Lu (2016). Deposition of size-selected nanoclusters. University of Birmingham. Ph.D.

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Abstract

The work presented in this thesis explores the production and the controlled deposition of size-selected nanoclusters. The size-dependent propagation of gold nanoclusters is investigated by depositing them through few-layer graphene (FLG) using a magnetron sputtering cluster source. Au55 nanoclusters penetrate through the FLG, however Au923 nanoclusters remain on the surface, as imaged by aberration corrected scanning transmission electron microscope (ac-STEM). The control of the atomic structure of gold nanoclusters (Au923) by systematically varying the gas-phase condensation parameters in the magnetron sputtering cluster source (e.g. magnetron power and condensation length) is also reported. Results show we have the ability to eliminate all icosahedral isomers by tuning the formation conditions. The biggest advance reported in the work concerns the new technology of the Matrix Assembly Cluster Source (MACS), which has the potential to increase the production rate of nanoclusters by 7 orders of magnitude from 0. 1-1 nA (from a magnetron source) to 1-1 Om A. The principle of the MACS is demonstrated by the production of Ag and Au clusters. The development of the latest MACS instrument is also described. An equivalent cluster beam current of ~ 1OOnA has been achieved. Gold and silver clusters produced under controlled experimental conditions show a relatively narrow size distribution even without mass selection (at best ±25% in the number of atoms). The mean cluster size can be controlled via the experimental parameters, especially the metal concentration in the matrix. STEM is again the principal tool employed characterize the number and structure of cluster produced by the MACS.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):