Stability of small chemical groups on hexagonal-SiC(0001) surfaces: A theoretical study

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• 作者：F. Spillebout^a ; L. Stauffer^a ; Ph. Sonnet^a ; ^{philippe.sonnet@uha.fr} ; A.J. Mayne^b
• 关键词：Silicon carbide surfaces ; Adsorption ; DFT calculations ; Surface properties
• 刊名：Surface Science
• 出版年：2012
• 期刊代码：104_00396028
• 类别：ch
• 出版时间：August, 2012
• 卷：606
• 期：15-16
• 页码：1195-1202
• 文件大小：1034 K

摘要

Density functional theory (DFT) calculations are used to investigate the stability on SiC(0001) surfaces of different chemical groups -NH₂, -NO₂, -CH₃, -OH, -SH and -CN. The adsorption stability decreases in the order -NO₂ > 鈭?#xA0;OH > 鈭?#xA0;NH₂ > 鈭?#xA0;SH > 鈭?#xA0;CN > 鈭?#xA0;CH₃. The stability of the single molecule-substrate bond is strongly influenced by the polarizability, which in turn depends on different parameters such as the electronegativity, atomic size and chemical environment. In a further step, methyl (鈭?#xA0;ACH₃) and phenyl (鈭?#xA0;AC₆H₅) substituted groups are also considered and similar behaviour is observed. The inductive effect of the -CH₃ or -C₆H₅ groups modifies the polarization of the Si adatom-molecule bond and the steric hindrance due to their size influences the molecular orientation. These two parameters affect the calculated adsorption energy, and are more important for -C₆H₅ substituent. This study provides clear tendencies that can be applied to more complex systems. Comparison of the adsorption of two large molecules, H₂Pc (metal-free phthalocyanine) and PTCDI (perylene tetracarboxylic diimide) on the SiC(0001) surface is presented as an example.