RESUMO
The design and fabrication of well-defined nanostructures have great importance in nanoelectronics. Here we report the precise growth of sub-2 nm (c-diamond) and above 5 nm (n-diamond) size diamond grains from energetic species (chemical vapor deposition process) at low growth temperature of about 460 °C. We demonstrate that a pre-nucleation induced interface can be accounted for the growth of c-diamond or n-diamond grains on Si-nanoneedles (Si-NN). These preferentially grown allotropic forms of diamond on Si-NN have shown high electron field-emission properties and signify their high potential towards diamond-based electronic applications.
RESUMO
La(Mg(0.5)Ti(0.5))O(3) (LMT) ceramics were prepared by either the solid-state reaction (LMT)(SS) or the citric-acid chemical method (LMT)(CA). A combination of Raman scattering, infrared reflectivity, and first-principles calculations was carried out to elucidate the correlation between lattice dynamics and the dielectric properties of these materials. Twelve Raman-active phonons are observed in both samples, displaying similar frequency positions. Interestingly, the A(g) phonon (g(11) mode) of (LMT)(SS) at about 717 cm(-1) involving the oxygen octahedron breathing vibrations demonstrates a narrower linewidth, suggesting its better crystallinity. Furthermore, an infrared-active u(2) phonon band due to the vibrations of O(I) and O(II) layers, which possesses the largest oscillator strength, exhibits stronger intensity for (LMT)(SS), as compared with those for (LMT)(CA). Additionally, the Q × f values (the product of dielectric Q values and measurement frequency) of (LMT)(SS) estimated from either microwave cavity or infrared spectroscopic measurements are larger than those of (LMT)(CA). These results indicate that the better coherence of lattice vibrations in (LMT)(SS) leads to its higher Q × f value, providing evidence for a strong connection between optical spectroscopic behavior and microwave dielectric characteristics in these materials.
RESUMO
Nanocrystalline diamond films prepared by microwave plasma enhanced chemical vapor deposition (MPECVD) were implanted using 110 keV nitrogen ions under fluence ranging from 10(13)-10(14) ions/cm2. Scanning Electron Microscopy (SEM) and Raman spectroscopy were used to analyze the changes in the surface of the films before and after ion implantation. Results show that with nitrogen ion implantation in nanocrystalline diamond film cause to decrease in diamond crystallinity. The field emission measurement shows a sharp increase in current density with increase in dose. The ion implantation also alters the turn on field. It is observed that the structural damage caused by ion implantation plays a significant role in emission behaviour of nanocrystalline diamonds.
RESUMO
Different forms of diamond have been shown to have qualities as field emission sources. As a consequence, much effort has been focused on both the synthesis of diamond nanostructures to increase the field enhancement factor and understanding the emission mechanism in these nominally insulating materials. In our recent study, we have grown ultrananocrystalline diamond (UNCD) coated nanocrystalline diamond (NCD) tips on NCD films for field emitters. The films were characterized using field emission scanning electron microscopy and Raman spectroscopy to identify the quality of the films. The fabricated different sizes of pyramid tips and their field emission properties are reported. It has been observed that with increase in tip size, the turn on voltage also increases.
