Structural and Optical Properties of Gold In MgO: Effects of Shape And The Interface
- PDF / 425,736 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 31 Downloads / 191 Views
Structural and Optical Properties of Gold In MgO: Effects of Shape And The Interface Elana M. Bryant, Akira Ueda, Richard R. Mu, Marvin H. Wu, Alkiviathes Meldrum1 and Don O. Henderson Chemical Physics Laboratory, Department of Physics, Fisk University, Nashville, TN 37208, USA 1 Department of Physics, University of Alberta, Edmonton, Alberta, Canada ABSTRACT The fundamental studies of metallic nanoparticles embedded in various host materials have been made. The host-guest interaction causes the shapes of embedded nanoparticles, and the surface plasmon resonances of the metallic nanoparticles are affected by the host materials. The control of the surface plasmon resonance condition is a challenging question. We will discuss the interface effect of the systems where gold nanoparticles were fabricated between materials of MgO and SiO2. INTRODUCTION Surface plasmon resonance (SPR) of small metallic particles has been studied since Mie’s idea of 1908 about the study [1] of optical properties of gold particles, and in the past three decades the new field of cluster science has been developed with many potential applications. Although many studies have been published, there are still new interesting systems and there are fundamental questions to be answered. In our laboratory, we have studied the systems of several insulating materials implanted with gold ions (Al2O3:Au, CaF2:Au, Silica SiO2:Au, MgO:Au, Muscovite Mica:Au, and Vycor Glass:Au) and of the porous materials impregnated with gold (Vycor Glass: Au)[2-5]. In the systems of SiO2:Au and MgO:Au fabricated by ion implantation, we have previously seen the growth of gold nanocrystals and found the SPR positions to be 530 nm and 560 nm, respectively, after a suitable thermal annealing in 5%O2+95%Ar atmosphere. These SPR positions agree with the Mie’s theory using a dipole approximation for spherical particles, that satisfies the following equation [6]:
ε (ω SP ) + 2ε m = 0 ,
(1)
where ε(ω) is the dielectric function of gold, εm is the dielectric function of host material, and ωSP is the surface plasmon frequency. As shown in figure 1, from our previous experiments, the gold nanocrystals in MgO have cubic shape, that aligns along the crystal axis of MgO (100), while the gold nanocrystals in SiO2 are spherical. (The detail of this result will be discussed elsewhere.) If only the surface energy of gold particles plays the C1.5.1
10 nm Figure 1 TEM image of Gold nanocrystals fabricated in MgO single crystal by ion implantation with a post annealing. The shape of the gold nanocrystals is cubic and they align along the crystal axis of host MgO (100).
dominant role for the nanocrystal growth, the shape should be spherical. The host MgO crystal, therefore, must contribute to this result of cubic gold particles because MgO single crystal has a cubic crystal structure. In this paper, we will discuss the interfacial interaction between gold nanocrystals and the dielectric hosts, in terms of dielectric constants and the crystal-amorphous character of host, by observing the SP
Data Loading...
