RESUMO
A large contrast in the electrical and thermal conductivities via a first order phase transition in surface-functionalized carbon nanotube(CNT)/hexadecane composites is reported. Surface modification of the CNTs improves the electrical conductivity contrast and the stability of the composites. We demonstrate that, with these composites, the electrical conductivity changes above 10(5) times and the thermal conductivity varies up to 3 times at 18 °C.
RESUMO
Er ions with 108 keV to a dose of 1 x 10(17) cm-2 were implanted into Si-rich thermal oxidation SiO2/Si thin film using metal vapor vacuum arc (MEVVA) ion source implanter. Er concentration in as-implanted sample, which was attained to -10 at % correspond to the level of -10(21) atoms.cm-3, was analyzed by Rutherford back-scattering (RBS) and X-ray photoelectron spectroscope (XPS). Contents of Er, Si and O in annealed samples were investigated using XPS at room temperature. It showed that Si content was increased and SiO2 content was decreased with increasing the fluence of Si ions. It was found by use dof reflective high energy electron diffraction (RHEED) and atomic force microscope (AFM) that needle micro-crystalline Si in the surface of annealed samples had been formed and Er segregation and precipitation were formed little. Photoluminescence around 1.54 microns from Er-doped Si-rich thermal oxidized SiO2/Si thin film were studied with a He-Cd laser pumping at 414.6 nm at the low temperature of 77 K and room-temperature (RT).
