| AVS 57th International Symposium & Exhibition | |
| Applied Surface Science | Tuesday Sessions |
| Session AS-TuA |
| Session: | Advances in Surface and Interface Imaging |
| Presenter: | S. Thevuthasan, Pacific Northwest National Laboratory |
| Authors: | S. Kuchihbatla, Pacific Northwest National Laboratory V. Shutthanandan, Pacific Northwest National Laboratory B. Arey, Pacific Northwest National Laboratory R. Ulfig, Cameca Instruments Inc. T. Prosa, Cameca Instruments Inc. C.M. Wang, Pacific Northwest National Laboratory S. Thevuthasan, Pacific Northwest National Laboratory P. Clifton, Cameca Instruments Inc. |
| Correspondent: | Click to Email |
The influence of embedded nanoclusters on the optical, magnetic and electrical properties of bulk and surface oxides has been an active area of investigation. The establishment of new atom probe tomography (APT) and related high-resolution chemical imaging facilities at EMSL, the Environmental Molecular Sciences Laboratory, provides a world-class user facility for performing nanoscale microscopy. In this study we report on Au-rich nanoclusters that have been embedded into MgO and TiO2 substrates. The effect of high temperature annealing on the properties of the matrix and the secondary phase (Au) are studied in detail. Electron microscopy analysis has shown that the embedded metal particles are often associated with various defects, which further contribute to property modification.
We report the first Local Electrode Atom Probe (LEAP®) analysis of bulk MgO and TiO2 implanted with 2 MeV Au ions using the accelerator facility at EMSL. Both as-implanted and annealed samples were critically analyzed using a combination of APT and the results are compared with high-angular annular dark-field scanning transmission electron microscopy (HAADF STEM) imaging. High-resolution transmission electron microscopy (HRTEM) clearly resolves the Au-rich nanoclusters and allows observation of the pronounced vacancy clustering associated with these features [1]. These Au-rich nanoclusters were also observed in the atom probe data with the average cluster size (~ 5 nm diameter) in good agreement with those seen using HRTEM. The APT technique, however, due to the high three-dimensional (3D) spatial resolution, is also able to detect the presence of finer-scale Au clusters. It can also directly measure residual Au composition within the MgO matrix and any MgO-Au mixing within the clusters. Besides variations in compositional microstructure, evolution of mass spectrum quality as a function of Au content is also observed. Efforts are ongoing in EMSL to confirm this observation and eliminate the possibility of any contribution from experimental artifacts.
During the course of this presentation we will highlight the advantages of using 3D APT in combination with electron microscopy. Specifically, correlative microscopy provides a means to evaluate the capability of APT to detect the presence of the vacancy clusters.
[1] Wang et al., Applied Physics Letters 87, 153104, 2005