Formation, Phase Transition And Optical Properties Of Silver-copper Alloy Clusters

Multicomponent metal clusters is often called "nano-alloy". The most important examples of bimetallic alloy nanoparticles are Ag-Au, Ag-Ti, Pd-Pt, Au-Pd and Ag-Cu. Alloy nanoscale materials show different structural and physical properties than bulk samples. Bimetallic nanoparticles are more attractive over monometallic nanocrystals because they exhibit improved electronic, optical and catalytic properties. Moreover, the change in composition of metals provides another dimension in tailoring the properties of bimetallic nanoparticles besides the usual size and shape manipulation hosts of new applications. Therefore, research on nano-alloy obtained more and more attention in recent yeas, particular on the formation mechanism of nano-ally, as well as on the control and tailoring of it’s nature. And the optical properties arising from the particle surface plasmon resonance (SPR) have been studied extensively.In this paper, we used the Ultra High Vacuum Cluster Beam System (UHV-CBS) to deposit the low-energy clusters by means of magnetron plasma gas aggregation to fabricate BM Ag-Cu NPs. We used double independent targets to control the composition of BM Ag-Cu NPs. And we prepared the BM Ag-Cu NPs in two different ways. One is prepared by the step sputtering, the other is prepared by the co-sputtering.Transmission electron microscopy (TEM) was carried out with a JEOL JEM200EX operating at300keV on nanoparticles deposited on a carbon-coated copper grid and revealed the nanoparticle topology (size and size distribution).And we studied the XPS to find the chemical shates of atoms. The EDX mapping was used to study the chemical composition of the BM Ag-Cu NPs. And we found several structures of the BM Ag-Cu NPs.We studied the extinction spectrum of the BM Ag-Cu NPs in situ.And we found that their SPR could change a large range of wavelength within the two boundaries of the constituents as a result of the change in their composition and temperature. So we afford a new approach for better control of size and alloy composition of BM Ag-Cu NPs sputtering. And also afford a way to tune the SPR of BM Ag-Cu NPs for a large range of wavelength.