| Autor: |
Schall JD; Mechanical Engineering Department, North Carolina A & T University, Greensboro, North Carolina 27411, United States., Morrow BH; Chemistry Department, United States Naval Academy, Annapolis, Maryland 21402, United States., Carpick RW; Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States., Harrison JA; Chemistry Department, United States Naval Academy, Annapolis, Maryland 21402, United States. |
| Jazyk: |
angličtina |
| Zdroj: |
Langmuir : the ACS journal of surfaces and colloids [Langmuir] 2024 Mar 05; Vol. 40 (9), pp. 4601-4614. Date of Electronic Publication: 2024 Feb 07. |
| DOI: |
10.1021/acs.langmuir.3c02870 |
| Abstrakt: |
The contact between nanoscale single-crystal silicon asperities and substrates terminated with -H and -OH functional groups is simulated using reactive molecular dynamics (MD). Consistent with previous MD simulations for self-mated surfaces with -H terminations only, adhesion is found to be low at full adsorbate coverages, be it self-mated coverages of mixtures of -H and -OH groups, or just -OH groups. As the coverage reduces, adhesion increases markedly, by factors of ∼5 and ∼6 for -H-terminated surfaces and -OH-terminated surfaces, respectively, and is due to the formation of covalent Si-Si bonds; for -OH-terminated surfaces, some interfacial Si-O-Si bonds are also formed. Thus, covalent linkages need to be broken upon separation of the tip and substrate. In contrast, replacing -H groups with -OH groups while maintaining complete coverage leads to negligible increases in adhesion. This indicates that increases in adhesion require unsaturated sites. Furthermore, plane-wave density functional theory (DFT) calculations were performed to investigate the energetics of two Si(111) surfaces fully terminated by either -H or -OH groups. Importantly for the adhesion results, both DFT and MD calculations predict the correct trends for the relative bond strengths: Si-O > Si-H > Si-Si. This work supports the contention that prior experimental work observing strong increases in adhesion after sliding Si-Si nanoasperities over each other is due to sliding-induced removal of passivating species on the Si surfaces. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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