Nanometric SiC Research Articles

Creation of internal point defect drains in silicon by carbon implantation

High-dose carbon implantations into silicon at temperatures between 150 and 250 °C result in the formation of a buried amorphous layer with a layer of self-organized nanometric amorphous SiC x precipitates and a completely crystalline Si top layer above. It is shown by RBS channeling and cross-sectional TEM that the nature of defects in the top layer critically depends on the implantation temperature and determines the annealing behaviour of amorphous SiC x precipitates. For lower implantation temperatures, when extended defects are absent in the top layer, 900 °C annealing leads to partial crystallization of amorphous SiC x precipitates, accompanied by void formation. Crystallizing SiC x precipitates then act as sinks for silicon self-interstitials. For higher implantation temperatures, dislocations on {1 1 1} planes and {3 1 1}-defects effectively trap the self-interstitials and inhibit the crystallization of amorphous SiC x . It is also shown that the crystallization temperature of SiC in the continuous buried amorphous layer depends on the implantation temperature.

Dispersion behaviour of laser-synthesized nanometric SiC powders in aqueous medium with ammonium polyacrylate

The dispersion behaviour of laser-synthesized nanometric SiC powders in water using ammonium polyacrylate (molecular weight=10,000) as dispersant was investigated. The influence of oxidation, presoaking time, ammonium polyacrylate (NH 4PA) concentration, and pH on suspension stability and coagulation rate of aggregates was determined. The stabilization mechanism is discussed. Excellent dispersion stability was obtained for oxidized (500 °C) powders containing 2.45 wt.% NH 4PA at pH 9.25 after a lengthy aging treatment.

Study of Blue Emission from Nano-SiC Powders During Rapid Thermal Annealing

Nanometric SiC powder was prepared by chemical vapor deposition at 1100°C, and samples were subsequently treated by rapid thermal annealing at 600-1100°C. The intensities of the blue photoluminescence were then measured at room temperature. The peak intensity at 2.56 eV (484 nm) rises with annealing temperature, reaching a value about 9.2 times as high at 800°C, then drops very quickly at 900°C. Based on the results of x-ray diffraction, infrared spectroscopy, x-ray photoelectron spectroscopy and transmission electron microscopy, we conclude that the amounts of the twofold coordinated Si on the surface of the nanometric SiC particles play an important role in the photoluminescence intensity.

Study of an Al Composite Reinforced with Nanometric SiC Particles, Produced by Mechanical Alloying

Study of an Al Composite Reinforced with Nanometric SiC Particles, Produced by Mechanical Alloying

Electron cyclotron resonance plasma ion beam effects on the formation of SiC on Si(001) characterized by in-situ photoemission

Nanometric SiC overlayer synthesis has been performed via an ultrahigh vacuum-compatible microwave electron cyclotron resonance plasma source. The H 2 plasma streaming onto a Si(001) substrate, whose temperature T s could be varied from room temperature to 850°C, activates and dissociates CH 4 molecules. The films are characterized in situ by angle-resolved photoemission techniques. Without the H 2 plasma, no surface reaction of CH 4 is observed with the Si irrespective of T s up to 850°C and exposures up to 10 6L. H 2 plasma excitation leads to the rapid formation of a thin SiC overlayer in the whole T s range. For temperatures below a threshold of about 700°C where thermal interdiffusion between Si and C is negligible, the SiC overlayer thickness rapidly saturates in the nanometric range and the SiC formed is not structured. This thickness is essentially determined by ion penetration in the substrate which can be increased by negative biasing. Above this T s, SiC growth increases rapidly and the film becomes textured near 800°C, as the growth of β-SiC(001) aligned with Si(001) can be observed. The SiC topmost-layer structure is critically dependent on the plasma conditions with respect to the thermal processing at the film growth interruption. When the plasma is switched off before heating, the surface is essentially Si rich and oxidizable. In the opposite case, the H 2 plasma etches the Si-terminated overlayer and passivates the surface.

X-ray photoelectron diffraction observation of β-SiC(001) obtained by electron cyclotron resonance plasma assisted growth on Si(001)

Nanometric SiC overlayer synthesis has been performed via a microwave electron cyclotron resonance (ECR) H 2 plasma activating CH 4 molecules on Si(001) substrates whose temperatures ( T s) expanded from room temperature to 850°C. The films were characterized in situ by angularly resolved photoemission techniques. In addition to the T s dependence of the growth kinetics obtained from conventional X-ray photoelectron spectroscopy (XPS) measurements, photoelectron diffraction (XPD) is used for the first time to show the appearance of textured growth of β- or 3C-SiC(001)∥Si(001) for T s above 800°C. To this end the structured polar scans of the C 1s and Si 2p carbide intensities are presented for the two (100) and (1 1 0) high-symmetry planes and compared to the corresponding Si substrate signatures. These data are relevant to the first XPD investigation of a binary compound with well differentiated diffusers such as C and Si atoms and identical environments under test in spite of which differentiated C 1s and Si 2p patterns are obtained.