| Autor: |
Neidhardt, J., Czigány, Zs., Brunell, I. F., Hultman, L. |
| Předmět: |
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| Zdroj: |
Journal of Applied Physics; 3/1/2003, Vol. 93 Issue 5, p3002, 14p, 3 Black and White Photographs, 1 Diagram, 3 Charts, 10 Graphs |
| Abstrakt: |
Fullerene-like (FL) carbon nitride (CN[sub x]) films were deposited on Si (100) substrates by dc reactive, unbalanced, magnetron sputtering in a N[sub 2]/Ar mixture from a high-purity pyrolythic graphite cathode in a dual-magnetron system with coupled magnetic fields. The N[sub 2] fraction in the discharge gas (0%-100%) and substrate bias (-25 V; -40 V) was varied, while the total pressure (0.4 Pa) and substrate temperature (450 °C) was kept constant. The coupled configuration of the magnetrons resulted in a reduced ion flux density, leading to a much lower average energy per incorporated particle, due to a less focused plasma as compared to a single magnetron. This enabled the evolution of a pronounced FL microstructure. The nitrogen concentration in the films saturated rapidly at 14-18 at. %, as determined by elastic recoil analysis, with a minor dependence on the discharge conditions. No correlations were detected between the photoelectron N1 s core level spectra and the different microstructures, as observed by high-resolution electron microscopy. A variety of distinct FL structures were obtained, ranging from structures with elongated and aligned nitrogen-containing graphitic sheets to disordered structures, however, not exclusively linked to the total N concentration in the films. The microstructure evolution has rather to be seen as in equilibrium between the two competing processes of adsorption and desorption of nitrogen-containing species at the substrate. This balance is shifted by the energy and number of arriving species as well as by the substrate temperature. The most exceptional structure, for lower N[sub 2] fractions, consists of well-aligned, multi-layered circular features (nano-onions) with an inner diameter of approximately 0.7 nm and successive shells at a distance of ∼0.35 nm up to a diameter of 5 nm. It is shown that the intrinsic stress formation is closely linked with the evolution and accommodation of the heavily bent... [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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