FORMATION OF NANOCLUSTER COLLOIDS OF TIN, GOLD AND COPPER IN MAGNESIUM OXIDE BY MeV ION IMPLANTATION R. L. ZIMMERMAN *, D. ILA *, E. K. WILLIAMS * and S. SARKISOV *, D. B. POKER ** and D. K. HENSLEY , *Center for Irradiation of Materials, Department of Natural and Physical Sciences, Alabama A&M University, P. 0. Box 1447, Normal, AL 35762-1447, ila@cim.aamu.edu "*Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 ABSTRACT We have implanted ions of Sn, Au and Cu at energies between 160 keV and 2.0 MeV into single crystals of MgO (100) at room temperature. The formation of nanoclusters was confirmed using photospectrometry, in combination with Mie's theory, which was indirect but nondestructive. Using Doyle's theory, as well as Rutherford Backscattering Spectrometry (RBS), we correlated the full width half maximum of the absorption bands to the estimated size of the metallic nanoclusters between 1-10 nm. These clusters were formed both by over implantation and by a combination of threshold fluence of the implanted species and post thermal annealing. The changes in the estimated size of the nanoclusters, after annealing at temperatures ranging from 500'C to 1000 0 C, were observed using photospectrometry. INTRODUCTION The classical treatment of small spheres imbedded in an optical material of index n. shows that an imposed electric field produces in each sphere a dipole moment proportional to the field and to the factor 2 s-no +2n(1) where 6 is the dielectric constant of the material of the spheres. For spheres of conducting material E = & 1 + j 6 2 , where the real component F, is negative and the imaginary component F, 2 is proportional to the conductivity which causes energy loss from a time varying electric field, such as that in visible light. Mie [1] derived the optical absorption coefficient (x of a material with a volume fraction Q occupied by metal spheres whose radii are small compared with incident light of wavelength 2, 187tQ2no 3 2 0 62 cm'-. (2) A minimum occurs in the denominator of Equation 2 when , I (Xp) + 2n2 =0(3) and causes a maximum absorption of light at a characteristic wavelength Xp, the so called surface plasmon resonance [2-5]. Metallic colloids embedded in a dielectric transmit only part of the visible spectrum, a phenomenon used since ancient times to decorate glassware. Figure 1 shows the values of 81 and 82 for gold, silver, copper and tin derived from the electronic constants of the bulk metals [6,7]. The downward trend of 6i, linear in wavelength, together with the slow variation of 82 , leads us to expect quasi Lorentzian optical absorption peaks centered at a wavelength Xp characteristic of the index of refraction of the host and of the permittivity of the 375 Mat. Res. Soc. Symp. Proc. Vol. 504 © 1998 Materials Research Society