Синтез массивов углеродных нанотрубок с переменной плотностью

Abstract

The study is aimed at obtaining a sparse carbon nanotube (CNT) array for using it in experiments on amplifying the surface-enhanced Raman scattering (SERS) signal. A procedure for synthesizing CNTs on Si/SiO2 and on glass-ceramic (sitall) substrates using the CVD method has been developed. The substrates were covered with a thin Ni layer in a magnetron sputtering unit. The subsequent annealing of the substrates in a high-temperature furnace at a temperature of 800-1000 оС resulted in that the Ni film became decomposed into an array of Ni islands that served as CNT growth catalysts. The CNTs were synthesized in the Planar Tech unit’s automated high-temperature furnace in a quartz glass tube, which was placed in the furnace and streamlined by flow of Ar with admixture СН4, Н2 and NH The synthesis temperature was equal to 900 оС, and the total synthesis process took more than 200 min. Owing to the system’s being fully automated, the synthesis operating parameters could be set up, including the temperature and duration of each stage and composition of gas mixture blown through the quartz tube. The microimages of the CNT arrays grown on different substrates were analyzed, and it has been found from that analysis that the synthesis yielded horizontally oriented multilayer CNTs ranging from 26 to 60 nm in diameter, depending both on the substrate type and condition and the surface annealing conditions. These factors also determine the CNT array density on the substrate. The synthesis conditions under which a sparse CNT array is obtained, which seems to be the most suitable for carrying out experiments on amplifying the SERS signal, have been established. Peculiarities of the Raman signal enhancement as a result of interaction between plasmon oscillations in CNTs and polyatomic molecules in the presence of laser radiation are discussed. It is pointed out that neighboring nanotubes have a screening effect on the radiation, for avoiding which sparse CNT arrays need to be used.