Physics and Applications of Atomic Clusters

Richard E. Palmer, Nanoscale Physics Research Laboratory, The University of Birmingham

The controlled deposition of size-selected clusters creates new possibilities for the fabrication of both biochips and model catalysts [1]. I will discuss the translation of basic cluster-surface research into applications in both these cross-disciplinary areas. Knowledge and control of the 3D atomic structure of the cluster is relevant both to such applications and to the fundamental physics and chemistry of the clusters. Direct structural measurements of clusters in the gas phase are very challenging, so surface measurements after (gentle) deposition may also shed new and valuable light on the intrinsic cluster structure. I will discuss measurements of the incoherently scattered electron intensity ? the high angle annular dark field (HAADF) signal ? in the scanning transmission electron microscope (STEM), which allows us (a) to count the number of atoms in a cluster on the surface and (b) to determine a 3D atom-density map of the cluster when an aberration-corrected STEM is used [2]. Moreover, size-selected clusters can also be used as a mass standard to "weigh", for example, metal nanoparticles produced by other less precise (but sometimes more practical) methods as well as non-spherical, mass-selected clusters: this is mass spectrometry on the surface [3].

1. R.E. Palmer, S. Pratontep and H.-G. Boyen, Nature Materials 2 443 (2003); C. Leung, C. Xirouchaki, N. Berovic and R.E. Palmer, Advanced Materials 16 223 (2004); R.E. Palmer and C. Leung, Trends in Biotechnology 25 48 (2007).

2. Z.Y. Li, N.P. Young, M. Di Vece, R.E. Palmer, A.L. Bleloch, B.C. Curley, R.L. Johnston, J. Jiang, J. Yuan, Nature 451 46 (2008).

3. N.P. Young, Z.Y. Li, Y. Chen, S. Palomba, M. Di Vece and R.E. Palmer, Phys. Rev. Lett. 101 246103 (2008).

Richard E. Palmer
Nanoscale Physics Research Laboratory
The University of Birmingham
Birmingham B15 2TT, UK
r.e.palmer@bham.ac.uk
www.nprl.bham.ac.uk