'Spillout' effect in gold nanoclusters embedded in c-Al2O3(0001) matrix
  Gold nanoclusters are grown by 1.8 MeV Au^\sup{2+} implantation on c-Al\sub{2}O\sub{3}(0001)substrate and subsequent air annealing at temperatures 1273K. Post-annealed samples show plasmon resonance in the optical (561-579 nm) region for average cluster sizes ~1.72-2.4 nm. A redshift of the plasmon peak with decreasing cluster size in the post-annealed samples is assigned to the 'spillout' effect (reduction of electron density) for clusters with ~157-427 number of Au atoms fully embedded in crystalline dielectric matrix with increased polarizability in the embedded system. 
S. Dhara, B. Sundaravel, T. R. Ravindran, K. G. M. Nair, C. David, B.   K. Panigrahi, P. Magudapathy, and K. H. Chen