CVD SYNTHESIS AND THE STRUCTURE OF VERTICALLY ALIGNED CNT ARRAYS

The structure and morphology of vertically aligned CNT (VACNT) arrays grown by CVD on Fe-Al2O3/Si(001) substrates are studied using scanning and high-resolution transmission electron microscopy (HRTEM) methods and Raman scattering. It is established that reproducible growth of continuous VACNT arrays is achieved only if the deposited Fe layer is at least 2 nm thick, while the particle size of the catalyst formed by annealing at 700 degrees C varies in a range of 2-10 nm and the array consists mainly of single- and double-walled CNTs with a diameter of 1-6 nm. The Raman spectrum is characterized by the presence of a radial breathing mode in the region 95-232 cm(-1) and an intense G mode that is split into peaks at 1594 cm(-1) and 1568 cm(-1) upon laser excitation at the wavelength lambda = 785 nm. According to the literature data, both modes indicate predominantly semiconductor nature of tubes in the array. The measured surface resistance of the VACNT array is 320 +/- 20 Omega/square.