Preparation And Characterization Of Silicon Carbon Nanotube Arrays

The multi-walled carbon nanotubes (MWNTs) have been synthesized from the carbonaceous source of H2--CH4 mixtures by catalytic chemical vapor deposition (CVD) method in the presence of Ni metals. To utilize the anodic aluminum oxide (AAO) template the CNTs array has been fabricated on Si substrate. The morphology and structure of the samples we made were investigated by filed emission scanning microscope (FE-SEM)> atomic force microscope (AFEM) and Raman spectroscopy. All samples were analyzed and the parameters of CNTs synthesizing were achieved. As well as the optical characters of CNTs, third-order optical nonlinearity, Raman spectroscopy and polarization dependent optical absorption properties, were investigated. 1. Synthesis CNTs array on Si substrate by CVD methodThe instruments of synthesizing CNTs by pulse laser evaporation method in our lab have been changed into electric furnace applied to CVD. CNTs was synthesized from the carbonaceous source of H₂--CH₄ mixtures by catalytic chemical vapor deposition, Co and Ni metals as catalysts. The samples fabricated at vary conditions were characterized by FE-SEM, TEM and Raman spectroscopy. We have studied the effects of reaction conditions, the proportion of CH4 and H₂, temperature, catalysts and growth time upon synthesizing of CNTs.The well-ordered self-assume anodic aluminum oxide template (AAO) and AAO/Si template have been fabricated with the anodic instrument we made. AAO and AAO/Si were characterized by FE-SEM, AFM and X-ray energy spectroscopy. And we researched the dependents of anodic alumina parameters on the anodic conditions, which include electrolytes, temperature, current density and anodic time.The CNTs array on Si substrate has been grown with AAO/Si temperate by CVD method. In this experiment, we deposition catalysts particles on Si wafer through three methods: First the anodic alumina as temperate we deposited well-ordered pure Ni particles on Si wafer by thermo evaporation. The second, we AC electro-deposited Ni in the pores of AAO/Si from Ni(NO₃)₂ solution. The third, Ni particles was deposited directly on clean Si wafer by ion-beam evaporator. The three methods were compared toeach other and the samples analyzed by SEM and Raman spectroscopy. 2. Study on the optical properties of CNTsThe optical nonlinearity, Raman scanter and polarization optical absorption properties of CNTs we synthesized were investigated through experiments. We attained the third-ordered optical nonlinearity curves by the Z-scan instrument we designed. CNTs have strong optical nonlinearity. The Raman scanter spectruras of CNTs powder and CNTs array on Si substrate were measured by Raman spectroscopy, which was excitated by 632.8nm laser and 514.5nm laser. We analyzed and compared the spectrums of samples grew at vary conditions, which indicated that the CNTs structures strong depend upon the conditions of synthesis. The maximum of the integral intensities ration of the D and G band, Ig/Id. could reach to 3.43. As well as we got the curves of polarization optical absorption properties of CNTs, the wavelength of incidence light is 532nm applied by a continue output semiconductor laser. The experiment suggested that the absorption of light polarized paralleled to the tube axis (c//P) is strongest, while the absorption of light perpendicular (cLP) is weakest, so much as transparent.