RESUMO
We investigated the effect of annealing in a hydrogen atmosphere on carbon nanocap formation during decomposition of a 6H-SiC(000-1) surface. It was determined that native oxides were reduced to below the detection limit of X-ray photoelectron spectroscopy after 30 min of annealing at 1200 degrees C in a hydrogen atomosphere at 10(-3) Pa. In addition, we found that the homogeneity of carbon nanocap size was improved on the SiC surface, compared with a sample annealed in ultra-high vacuum. This technique will be useful in the fabrication of homogeneous carbon nanotube layers by surface decomposition of SiC.
RESUMO
Carbon nanotube (CNT) growth was carried out on SiO2/Si substrates with a Co catalyst using an alcohol gas source method in an ultra-high vacuum chamber. The resulting CNTs were characterized by scanning electron microscopy (SEM), Raman spectroscopy and transmission electron microscopy (TEM). Reducing the ethanol pressure decreased the optimum growth temperature for maximum yield, enabling single-walled carbon nanotube (SWNT) growth at 400 degrees C. By employing an Al2Ox buffer layer, SWNT yield increased several times, even at 400 degrees C. Under TEM observation, the Co particle size on the Al2Ox layers did not show a significant dependence on the growth temperature between 400 and 700 degrees C. Raman and TEM results confirmed activation of Co particles with larger diameter (>1 nm) by the Al2Ox buffer layer.
RESUMO
A (87)Rb hyperfine optical-pumping light source less than 4 cm long has been fabricated. Features of this new light source are: A 3-7-mm-long (85)Rb filter cell is attached to the front face of a cylindrical (87)Rb lamp with a diameter of 10mm, and both the lamp and the filter cell are operated at the same temperature of about 100 degrees C. A satisfactory spectral profile of D(1)-line output (lambda = 794.8 nm) has been observed by using a Fabry-Perot interferometer.