What atomic resolution annular dark field imaging can tell us about gold nanoparticles on TiO2 (1 1 0)

Institute of Engineering Innovation, The University of Tokyo, Tokyo 116-0013, Japan.
Ultramicroscopy (Impact Factor: 2.44). 08/2009; 109(12):1435-46. DOI: 10.1016/j.ultramic.2009.07.006
Source: PubMed


Annular dark field scanning transmission electron microscopy imaging was recently applied to a catalyst consisting of gold nanoparticles on TiO(2) (110), showing directly that the gold atoms in small nanoparticles preferentially attach to specific sites on the TiO(2) (110) surface. Here, through simulation, a parameter exploration of the imaging conditions which maximise the visibility of such nanoparticles is presented. Aberration correction, finite source size and profile imaging are all considered while trying to extracting the maximum amount of information from a given sample. Comment is made on the role of the thermal vibration of the atoms in the nanoparticle, the magnitude of which is generally not known a priori but which affects the visibility of the nanoparticles in this imaging mode.

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    • "Thus far, agreement between calculation and experiment requires knowledge of a significant number of imaging parameters , such as convergence angle, defocus and other residual aberrations [18]. In particular, a convolution with a Gaussian is routinely used to account for the finite size of the electron source and its broadening effect on the probe [19]. Often, the width of this Gaussian is found through an empirical fit to achieve an exact match of the simulations with the data [17], and subsequent experiments with different samples can then be used to show a consistent measure of the probe size of a particular instrument [2] [20] [21]. "
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