期刊
ACS APPLIED MATERIALS & INTERFACES
卷 14, 期 5, 页码 7152-7160出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsami.1c21640
关键词
vertical graphene; plasma-enhanced chemical vapor deposition; GaN nanowires; nanoparticles; 2D materials
资金
- Fujian provincial projects [2021HZ0114, 2021J01583, 2021L3004]
- National Natural Science Foundation of China [62175032]
- Novo Nordisk Foundation [NNF10CC1016517]
- Independent Research Fund Denmark-FTP
- Nord Forsk
- Mindu projects [2021ZZ122, 2020ZZ110]
The study reveals that vertically oriented graphene preferentially grows in areas with stronger local electric fields during plasma-enhanced chemical vapor deposition. The electric field helps accumulate charges on graphene, transforming cohesive graphene layers into separate three-dimensional VG flakes. Additionally, the field attracts charged precursors to protruding areas on the substrate, aiding in the formation of VG.
Vertically oriented graphene (VG) has attracted attention for years, but the growth mechanism is still not fully revealed. The electric field may play a role, but the direct evidence and exactly what role it plays remains unclear. Here, we conduct a systematic study and find that in plasma-enhanced chemical vapor deposition, the VG growth preferably occurs at spots where the local field is stronger, for example, at GaN nanowire tips. On almost round-shaped nanoparticles, instead of being perpendicular to the substrate, the VG grows along the field direction, that is, perpendicular to the particles' local surfaces. Even more convincingly, the sheath field is screened to different degrees, and a direct correlation between the field strength and the VG growth is observed. Numerical calculation suggests that during the growth, the field helps accumulate charges on graphene, which eventually changes the cohesive graphene layers into separate three-dimensional VG flakes. Furthermore, the field helps attract charged precursors to places sticking out from the substrate and makes them even sharper and turn into VG. Finally, we demonstrate that the VG-covered nanoparticles are benign to human blood leukocytes and could be considered for drug delivery. Our research may serve as a starting point for further vertical two-dimensional material growth mechanism studies.
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