Nanostructural Evolution of Au on Silica Surfaces Exposed to Low Energy Ions*
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0929-II04-04
Nanostructural Evolution of Au on Silica Surfaces Exposed to Low Energy Ions* Volha Abidzina1, I. Tereshko1, I. Elkin2, R.L. Zimmerman3, S. Budak3, B. Zheng3, C. Muntele3, and D. Ila3 1 Belarusian-Russian University, Prospect Mira 43, Mogilev, 212005, Belarus 2 'KAMA VT' Research and Production Enterprise, Karl Libknecht Str. 3a, Mogilev, 212000, Belarus 3 Center for Irradiation of Materials, Alabama A&M University, Normal, AL, 35762-1447 ABSTRACT
We studied the effects of the low energy ions to induce nucleation of nanoscale crystals on and near surface of silica nano-layer containing low concentrations of Au. Suprasil substrates were coated with thin layer of gold followed by low-energy ion irradiation in glow discharge plasma. The formation of nanoscale crystals due to low energy ion irradiation was then studied using RBS and optical absorption spectrometry. INTRODUCTION
During the last decade, metallic ion implantation and thermal annealing have been used to change the linear and the non-linear optical properties near the surface of silica glass [1-8]. An attractive property of ion implantation is that ions can be focused in a well-defined space in an optical device, to induce local changes in its linear and nonlinear properties. The classical treatment of small spheres imbedded in an optical material of index no shows that an imposed electric field produces in each sphere a dipole moment proportional to the field and to the factor ε − n2o , (1) ε + 2n 2 o where ε is the dielectric constant of the material of the spheres. For spheres of conducting materials ε= ε1 + jε2, where the real component ε1 is negative and the imaginary component ε2 is proportional to the conductivity which causes energy loss from a time varying electric field, such as that in visible light. Mie [8] derived the optical absorption coefficient α of a material with a volume fraction Q occupied by metal spheres whose radii are small compared with incident light of wavelength λ ε2 18πQ 2n 3 o (cm-1) (2) α= ⋅ 2 2 2 λ (ε 1 + 2n o ) + ε 2 A minimum occurs in the denominator of equation (2) when
ε 1 (λ p ) + 2n 2 o = 0
(3)
and causes a maximum absorption of light at a characteristic wavelength λp, the so called surface plasmon resonance [1, 2]. Doyle [9] showed that for spheres whose size less than the mean free path of the conduction electrons the plasmon resonance is broader not by conductivity, represented by ε2, of the bulk material but by the radius r of the spheres. For the full width at half maximum ∆λ of the peak determined from an optical absorption measurement v f λ2 p r= , (4) 2πc∆λ where vf is the electron velocity corresponding to the Fermi energy of the metal. λp depends on the substrate and the element implanted it in and ∆λ is related to the size of the nanoclusters. Using Mie’s and Doyle’s theories is in good correlation with our previous works obtained by TEM [10, 11]. Changes in the optical properties of insulating materials can be made either by MeV bombardment or by heat treatment. The aim of this paper is
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