Study On Optimization And Sensing Property Of The Ultra-thin DLC Film/Ag Nano Particle Lspr Interface

In this paper, ultra-thin diamond-like carbon (DLC) film was deposited on the ITO glass substrate by the radio-frequency plasma enhanced chemical vapor deposition (RF PECVD) device. The deposition time of the ultra-thin DLC film was controlled within1minute. By changing the deposition technology parameters, such as RF power, distance between the electrode plates, etc, the ultra-thin DLC film had been formed due to reduced the deposition rate. In order to determine the optimal deposition technology parameters of the ultra-thin DLC film with excellent mechanical and optical properties, the composition, microstructure, surface morphology and light transmittance of the ultra-thin DLC film had been tested.The experimental results showed that the optimal parameters were the RF input power600W, C4H10/Ar flow1.5/25, distance between electrode plates10cm, the basis vacuum degree1.5×10-2Pa. The shorter the ultra-thin DLC film deposition time was, the higher the sp3bond content of carbon atoms and light transmittance. Moreover, when the ultra-thin DLC film deposition time was over20s, it could cover the ITO glass substrates completely and also got suitable surface smoothness and uniform particles distribution. The surface morphologies of the ultra-thin DLC films deposited on different substrates had been also observed and the ITO glass and the biological glass were more suitable substrates for the deposition of the ultra-thin DLC film.By preparing Ag nanoparticles with about80nm diameter on the ITO substrate and then depositing the ultra-thin DLC film on the surface of them, the ultra-thin DLC films/Ag NPs LSPR interface had been formed. The surface morphology and the sensing sensitivity of the LSPR interface had been also tested. It were shown that the Ag NPs’ size became more uniform after deposition of the ultra-thin DLC film, the LSPR effect absorption peak of the Ag NPs showed red-shift and its peak shape became sharper. This phenomenon provides the experimental support to enhance resolution of LSPR sensor as well as prevent Ag Nps’ oxidation reaction. Because the dielectric constant around Ag NPs changed, the LSPR sensitivity of the ultra-thin DLC film/Ag NPs interface changed obviously and it reduced with increase of the thickness of the DLC film. When deposition time of the ultra-thin DLC films was15s, the sensitivity was70.39nm/RIU. But while the deposition time was1min, the sensitivity was obviously decreased. The shorter the deposition time of the ultra-thin DLC film, the higher the sensitivity of the ultra-thin DLC film/Ag NPs interface. The deposition time20s was selected by considering the surface morphology and optical property of the ultra-thin DLC film and the LSPR sensitivity was64.75nm/RIU.The sensing mechanism of the Au@Ag core-shell microstructure and the ultra-thin DLC films/Ag NPs LSPR interface had also discussed in this paper.