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Density Functional Study of the Effect of SiH 4 /GeH 4 and Si(001)/Ge(001) on Gas‐Surface Reactivity during Initial Dissociative Adsorption
Author(s) -
Lin Jyh Shing,
Lee LienFeng,
Chou WenChi
Publication year - 2003
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.200300089
Subject(s) - chemistry , reactivity (psychology) , adsorption , density functional theory , pseudopotential , molecular beam , analytical chemistry (journal) , atomic physics , computational chemistry , molecule , organic chemistry , medicine , physics , alternative medicine , pathology
Ultrasoft pseudopotential total energy calculation based on density functional theory (DFT) with generalized gradient approximation (GGA) has been used to investigate 1) the energetic profile for the initial dissociative adsorption of XH 4 (X = Si and Ge) onto Si(001) and Ge(001) surfaces to evaluate their gas‐surface reactivity in comparison with relevant measured gas‐surface reactivity using supersonic molecular beam techniques, and 2) the effect of different gaseous molecular precursors, i.e. XH 4 (X = Si and Ge), and different surfaces, i.e. Si(001) and Ge(001), on their gas‐surface reactivity during initial dissociative adsorption. Our evaluated gas‐surface reactivity for GeH 4 is approximately a factor of 18.45 better than that for SiH 4 on Si(001)‐(2×2) surface. This calculated result is about three to four times higher than observed gas‐surface reactivity (as much as a factor of 5 depending on the incident kinetic energy) derived from measured gas‐surface reactivity using supersonic molecular beam techniques. We believe that the better evaluated gas‐surface reactivity for GeH 4 than SiH 4 is due to 1) the forming of a stronger bond of Si‐H between H within GeH 4 and buckled‐down Si atom on the Si(001)‐(2×2) surface and 2) the smaller distortion of Ge‐H bond within GeH 4 at the transition state. Additionally, our evaluated gas‐surface reactivity for SiH 4 on Si(001)‐(2×2) surface is approximately a factor of 21.69 better than SiH 4 on Ge(001)‐(2×2) surface. This calculated result is about two times higher than observed gas‐surface reactivity. We attributed this better evaluated gas‐surface reactivity for SiH 4 on Si(001)‐(2×2) surface to 1) the smaller distortion of Si‐H bond within SiH 4 and 2) the nature of weaker bond of Ge‐H between H within SiH 4 and buckled‐down Ge atom on Ge(001)‐(2×2) surface in comparison with that of stronger bond of Si‐H between H within SiH 4 and buckled‐down Si atom on Si(001)‐(2×2) surface even though there is the slightly shorter bond length of Ge‐H between H within SiH 4 and buckled‐down Ge atom on Ge(001)‐(2×2) surface at the transition state.