Study on the adsorption mechanism of hydrogen molecules on the surface of silicon carbide
In the process of CVD deposition of SiC,the reaction of carrier gas H2 with the surface of the deposi-ted SiC matrix affects the deposition rate and the quality of the deposited products,so it is of great theoretical and practical significance to study these microscopic reaction mechanisms.The adsorption locations,adsorption ener-gies,electronic structures and coverages of H2 on 3 C-SiC(111)(above it is the surface of a silicon atom)and 3C-SiC(111)(above it is the surface of the carbon atom)planes were studied using the first principles based on density functional theory.The results show that the most stable adsorption position of H atom is the OT posi-tion(on top)and belongs to chemical adsorption.Upon adsorption H2 spontaneously dissociates into two H at-oms which are adsorbed on two adjacent Si atoms in the form of a double top position,thus the electrons of the Si atoms on the surface of the matrix are shifted to H,where the main interaction between the two stems from the o-verlapping hybridization of the p-orbital of the Si atom and the s-orbital of H.By calculating the coverage of hydrogen on the surface,it is found that the adsorption energy increases with the increase of the coverage,under the low H coverage rate(θH≤4/9 ML),there is a strong attraction between H atoms,with the increase of H coverage(θH＞4/9 ML),the repulsion force between H atoms gradually increases,the adsorption energy increa-ses slowly,and the overall structure tends to be more stable.
First principlesSiCHydrogen moleculesCoverageAdsorption energy
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