Carbonization process of Si(100) by ion-beam bombardment

The evolution of carbonization process on Si as a function of ion dose has been carried out by mass-selected ion-beam deposition technique. 3C-SiC layer has been obtained at low ion dose, which has been observed by reflection high energy electron diffraction and X-ray photoelectron spectroscopy (XPS). The chemical states of Si and carbon have also been examined as a function of ion dose by XPS. Carbon enrichment was found regardless of the used ion dose here, which may be due to the high deposition rate. The formation mechanism of SiC has also been discussed based on the subplantation process. The work will also provide further understanding of the ion-bombardment effect. (C) 2001 Published by Elsevier Science B.V.

Promoting carbonization of polypropylene during combustion through synergistic catalysis of a trace of halogenated compounds and Ni2O3 for improving flame retardancy

The effect of combination between a trace of halogenated compounds (such as ferric chloride and ammonium bromide) and Ni2O3 particles on the carbonization of polypropylene (PP) was investigated during combustion. The results showed a synergistic catalysis of combined halogenated compounds with Ni2O3 in promoting the formation of the residual char during combustion. The investigation on the promotion mechanism showed that halide radical releasing from halogen-containing additives worked as a catalyst to accelerate dehydrogenation-aromatization of degradation products of PR which promote the degradation products to form the residual char catalyzed by nickel catalyst.

The growth of SiC on Si substrates with C2H4 and Si2H6

SiC was grown on Si (100) substrates oriented and off-oriented by 2-5 degrees towards [011] with simultaneous supply of C2H4 and S2H6 at 1050 degrees C. SiC formed during removal of oxide could be removed at 1150 degrees C. Twinned growth occurred on both oriented and off-oriented substrates during carbonization, but fewer twins formed on the off-oriented substrate than that on the oriented substrate. In SiC growth process, twinned growth continued on the off-oriented substrate whereas twinned growth stopped and single crystal SiC with double-domain (2 x 1) superstructure formed on the oriented substrate. SiC single crystal could grow on a carbonized twinned buffer layer. Obvious SiC LO and TO phonon modes were observed with Raman spectroscopy in the epilayer grown on the oriented substrate. The surface of the epilayer grown on the oriented substrate was smooth, while there was a high density of islands on the epilayer grown on the off-oriented substrate. The film grown on the oriented substrate is superior than that grown on the off-oriented substrate. (C) 1999 Elsevier Science B.V. All rights reserved.

The effects of carbonized buffer layer on the growth of SiC on Si

Carbonized buffer layers were formed with C2H4 on Si(100) and Si(111) substrates using different methods and SIC epilayers were grown on each buffer layer at 1050 degrees C with simultaneous supply of C2H4 and Si2H6. The structure of carbonized and epitaxy layers was analyzed with in situ RHEED. The buffer layers formed at 800 degrees C were polycrystalline on both Si(100) and Si(111) substrates whereas they were single crystals, with twins on Si(100) and without tu ins on Si(111)substrates. when formed with a gradual rise in substrate temperature from 300 degrees C to growth temperature. Raising the substrate temperature slowly results in the formation of more twins. Epilayers grown on carbonized polycrystalline lavers are polycrystalline. Single crystal epilayers without twins grow on single crystalline buffer layers without twins or with a few twins. (C) 1999 Elsevier Science B.V. All rights reserved.

Effects of metal catalysts on CO2 gasification reactivity of biomass char

The effects of five metal catalysts (K, Na, Ca, Mg, and Fe) on CO2 gasification reactivity of fir char were studied using thermal gravimetric analysis. The degree of carbonization, crystal structure and morphology of char samples was characterized by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The CO2 gasification reactivity of fir char was improved through the addition of metal catalysts, in the order K>Na>Ca>Fe>Mg. XRD analysis indicated that Na and Ca improved the formation of crystal structure, and that Mg enhanced the degree of carbon structure ordering. SEM analysis showed that spotted activation centers were distributed on the surface of char samples impregnated with catalysts. Moreover, a loose flake structure was observed on the surface of both K-char and Na-char. Finally, the kinetic parameters of CO2 gasification of char samples were calculated mathematically.

Heteroepitaxial Growth and Heterojunction Characteristics of Voids-Free n-3C-SiC on p-Si(100)

Highly oriented voids-free 3C-SiC heteroepitaxial layers are grown on φ50mm Si (100) substrates by low pressure chemical vapor deposition (LPCVD). The initial stage of carbonization and the surface morphology of carbonization layers of Si(100) are studied using reflection high energy electron diffraction (RHEED) and scanning electron microscopy (SEM). It is shown that the optimized carbonization temperature for the growth of voids-free 3S-SiC on Si (100) substrates is 1100 ℃. The electrical properties of SiC layers are characterized using Van der Pauw method. The I-V, C-V, and the temperature dependence of I-V characteristics in n-3C-SiC-p-Si heterojunctions with AuGeNi and Al electrical pads are investigated. It is shown that the maximum reverse breakdown voltage of the n-3C-SiC-p-Si heterojunction diodes reaches to 220V at room temperature. These results indicate that the SiC/Si heterojunction diode can be used to fabricate the wide bandgap emitter SiC/Si heterojunction bipolar transistors (HBT's).