| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程系 === 97 === The adsorption and reaction of H2S on Si(100)-c(4x2) surface and Ge/ Si(100)-c(4x2) surface have been investigated using density functional theory (DFT) calculations. In this study, we have considered molecular, partially and fully dissociative adsorptions on both surfaces, and there are four reaction pathways from molecular absorption to fully dissociative adsorption were determined based on DFT calculation. DOS analysis indicates that Si(100) surface and Ge/Si(100) surface own similar characteristic. Both of them, the c(4×2) phase is the most stable surface.
We have discovered that the fully dissociated H2S on Si(100)-c(4×2) surface could be more stable through H migration and Si-S-Si ring formation. On Si(100)-c(4×2) surface, our calculated results indicate that the lowest rate-determining reaction barrier for H2S to form the final product is 1.19 eV, which such pathway is kinetically favorable. On the other hand, we have found the most stable thermodynamically favored product, whereas its rate-determining reaction barrier is high, 1.60 eV.
On the Ge/Si(100) surface, the calculations reveal a great difference to Si(100) surface, i.e. the partial dissociative adsorption minima are quite stable compared to fully dissociative ones. Three of the final states have approximately similar energy within 0.08 eV. The lowest rate-determining reaction barrier is 1.23 eV, and its final state is the second stable species of four final states. The highest rate-determining reaction barrier is 1.53 eV and its product is the least stable. In addition, the H2S molecule desorption from Ge/Si(100) surface would compete with the following reactions.
|
|---|
