Orientation dependent adsorption on a cylindrical silicon crystal

Ranke, W.; Xing, Y.R.

doi:10.1016/0167-2584(85)91099-0

Cited by 1 publication

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“…Compared to other silicon surfaces, the Si(111)-7 × 7 surface exhibits a diversity of reactive sites, serving as a good platform for understanding silicon surface chemistry. Over the past decades, the interaction of H 2 O with the Si(111)-7 × 7 surface has continuously attracted considerable attention not only from fundamental interest but also from technological importance in the microelectronics industry. − Earlier fundamental studies mainly focused on whether the adsorption of H 2 O on the Si(111)-7 × 7 surface is molecular or dissociative. − There has now been a majority opinion among these results that H 2 O dissociates to form the Si–H and Si–OH species on Si(111)-7 × 7. ,,,, Using a scanning tunneling microscope (STM), Avouris and Lyo first asserted that the adjacent adatom–rest atom (Si a –Si r ) dangling bond pair is involved in the splitting of a H 2 O molecule into the −OH and −H fragments. However, controversy still exists regarding on which site the dissociative adsorption of H 2 O initiates preferentially.…”

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confidence: 99%

Oxidation Mechanism of Si(111)-7 × 7 by Water: A Theoretical Study

Wang

Duan

2013

J. Phys. Chem. C

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Density functional theory at the level of (U)B3LYP has been used to investigate the complete oxidation of the Si(111)-7 × 7 surface by water. The results suggest that the initial water dissociation readily occurs across an adjacent adatom–rest atom (Sia–Sir) pair, resulting in either Sia–OH + Sir–H (i.e., the Sia route) or Sir–OH + Sia–H (i.e., the Sir route). Both routes are found to follow the precursor-mediated pathway, while the Sir atom is concluded to be more reactive than the Sia atom toward the initial decomposition of the H2O molecule due to its higher binding affinity to the incident water. With increasing water exposure and reaction temperature, deep oxidation can be accomplished by steady oxygen atom insertion into the Sia–Sis backbonds until the Si4+ oxidation state is eventually developed. Our calculations uncover that the most favorable pathway for deep oxidations begins with the direct water dissociation over the Sia–Sis backbond, followed by H2 liberation. This differs from the recent proposal via the OH insertion. Our deep oxidation mechanism can also be applied to the oxidation of an isolated adatom, which gives an explanation to the experimental observation where more than 50% of Sia are involved in water oxidation. The present work provides the detailed energetics that sheds light on the wet oxidation mechanism of silicon surfaces at the molecular level.

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