Vapor-growth carbon and the origin of carbonaceous material in ureilites

摘要

We synthesized carbon products by the Modified Hot Filament Chemical Vapor Deposition (MHFCVD) method in an artificial atmosphere containing noble gases, and measured the noble gas abundances trapped in them. MHFCVD carbon synthesized at high voltage contained large amounts of noble gases enriched in heavy noble gases. The trapping efficiencies of noble gas were the highest among those reported for synthetic samples in laboratory experiments. The elemental abundance patterns are similar to those in Microwave Chemical Vapor Deposition (MWCVD) diamonds, but show severe depletions of Ne. Synthesized (MHFCVD) carbon samples have similar noble gas features to those in diamond-free ureilites. This result suggests that amorphous carbon in diamond-free ureilites was also formed by Chemical Vapor Deposition (CVD), and that noble gases were implanted into amorphous carbon as well as into diamond in ureilites under plasma conditions.