Studies To The Preparation And Characterization Of SERS Active Substrates By Magnetron Sputtering

Raman spectrum using photon as probe is a vibrating spectrum related directly to the molecular structure, which is known as the fingerprint spectrum of material structures. Any tiny changes of structures can be sensitively reflected in Raman spectrum; therefore, it is widely used in physics, chemistry, biology and law fields of molecular structure, quality control, archaeology and so on. However, in general, Raman signals are very weak. Therefore, The developments of surface enhanced Raman Scattering (SERS) technique greatly enhance the scatter section, leading to the improvement of sensitivity.Currently, there are many kinds of SERS-active substrates used in the wide range of SERS applications. Some examples are metal hydrosols, vacuum evaporated metal surfaces and mechanically polished metal surfaces. The colloid prepared by reduction is easily obtained, but there are many disadvantages such as complex components, impurity and so on. The colloids prepared by laser ablation are very pure, but the yield is not enough. Rough surface is normally prepared by physical rubbing or chemical eroding. But there are also disadvantages such as hangover, rudimental impurities, difficult control, and so on. So we extend the SERS-active substrate by magnetron sputtering.Magnetron sputtering technique as a new sputtering technique that has developed in 70s last century and now it is widely used in the scientific research and modern industry. Magnetron sputtering films are mainly used in electronic industry, magnetism material, record medium, optical communication and so on, which has many advantages, such as high speed, low temperature and low damnification. Low temperature and low damnification is very important to protect the roughness of the substrate. These advantages make it easy to prepare the SERS-active films whose surface roughness are from several nanometers to several hundreds nanometers by changing the sputtering conditions such as pressure, electricity, time and anneal technics. Its repetition and stability is well. At last the substrates made by magnetron sputtering are very pure because they are sputtering in a super high vacuum environment.In this paper, technics of preparing are first studied for getting the substrates that we want. In order to investigate the SERS-active substrates' characters, we prepared the films of transitional metal Fe and Ti, noble metal Ag and Cu, Al and also semiconductor Si by magnetron sputtering. The atomic force microscope (AFM) was used to get the top view pictures of the films. And we also studied the SERS mechanism of different films by absorbing PHBA molecules on them. By comparing the AFM pictures with the SERS spectra of PHBA on the films, we discuss the characters of our substrates. At the end of the paper we study the SERS theory by Density functional theory (DFT) theoretic calculating.