WP1 SPELS calibration on e-beam lithography samples: Task 1 – prepare nanostructures by e-beam lithography. The instrument used for e-beam lithography broke during the project. Instead, Ag nanoplates with well-defined plasmon resonances were purchased from NanoComposix. These triangular nanoplates are 10 nm thick and 40 nm to 130 nm wide, and have different plasmon modes at their centres and corners. Task 2 – preliminary SPELS measurements on thermally evaporated Ag nanostructures. STM measurements could not be obtained on polyvinylpyrrolidone (PVP) capped Ag nanoplates due to the polymer, a smaller stabilising molecule (lipoic acid) was used. STM images were obtained but SPELS measurements of these nanostructures have not yet been performed. A new cylindrical sector analyser, having improved energy resolution, was designed in conjunction with LK technologies. Task 3 – statistical process control over tip production. A procedure for preparing electrochemically etched tungsten field emitters was developed, using an in-vacuum tip preparation stage tips were flash annealed in order to remove surface oxides, followed by field-induced sharpening.
WP2 SPELS measurements on epitaxial alloy films: Task 1 – build a temperature programmed desorption setup. Due to the need to design and assemble a working electron energy analyser, building the temperature programmed desorption was put on hold. Task 2 – SPELS measurements on epitaxial thin films. SPELS measurments were performed on the Au(111) surface where the characteristic plasmon loss feature at 2.6 eV was observed. A home-built electron beam evaporator was assembled and tested for in-situ thin film deposition. Task 3 – microfabrication of co-axial tips. No co-axial tips were microfabricated during the reporting period.
WP3 SPELS on nanoparticles: Task 1 – Produce size-selected Pt clusters. Pt923, Au923 and Pt147 nanoparticles were deposited onto graphite substrates using the inert gas aggregation source. Task 2 – Produce alloy nanoparticles. Co-deposition of Pt and Au nanoparticles produced PtAu nanostructures. Task 3 – SPELS of alloy nanoparticles. The BSE signal from the nanoparticles was lower than that obtained from the surrounding graphite substrate.The Pt and Au could not be distinguished in BSE images due to their similar atomic numbers. A small offset was observed between the same nanoparticle features in simultaneously acquired CFEC and BSE images, which was independent of the scan direction. This confirms that the BSE are detected from a probe area adjacent to the tip, and not from the region directly under the tip apex due to field suppression. Preliminary SPELS measurements of the energy loss spectrum of the PtAu nanostructures could not resolve the plasmon loss feature attributed to Au. Task 4 – optimise magnetron targets for producing homogeneous nanoparticle ensembles. This work was not completed due to the early termination of the project.
WP4 Training & Dissemination activities: Task 1 – Website. A website related to the project has been established at
http://snapcatweb.wordpress.com(opens in new window). Task 2 – Public outreach. Dr. Murphy established a profile on ResearchGate with details of the project and relevant publications. Task 3 – Training & secondment. Dr. Murphy received some training in the operation of the gas aggregation cluster source. He has also learned some programming in Python in order to process the SPELS data. He attended several seminars by invited speakers who are experts in the field of nanoparticle synthesis and characterisation and microscopy. Task 4 – Conference. Dr. Murphy has recently attended the Microscience and Microscopy Congress (mmc2017) in Manchester. Task 5 – Papers. A paper reporting the preliminary results on imaging size-selected nanoparticles with SPELS is in preparation.
