| 1. |
- Sun, Jie, 1977, et al.
(författare)
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Insights into the Mechanism for Vertical Graphene Growth by Plasma-Enhanced Chemical Vapor Deposition
- 2022
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Ingår i: Acs Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 14:5, s. 7152-7160
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Tidskriftsartikel (refereegranskat)abstract
- 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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| 2. |
- Vyas, Agin, 1992, et al.
(författare)
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Investigation of palladium current collectors for vertical graphene-based microsupercapacitors
- 2019
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 1319:1
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Konferensbidrag (refereegranskat)abstract
- As microsystems are reduced in size and become integrated in the Internet of Things (IoT), they require an adequate power supply which can be integrated at the same size scale. Microsupercapacitors (MSCs), if coupled with on-chip harvesters, can offer solutions for a self-sustaining, on-chip power supply. However, the implementation of reliable MSC wafer-scale production compatible with CMOS technology remains a challenge. Palladium (Pd) is known as a CMOS compatible metal and, in this paper, we investigate the use of Pd as a contact material for vertical graphene (VG) electrodes in wafer-scale MSC fabrication. We show that a Ti diffusion barrier is required to prevent short-circuiting for the successful employment of Pd contacts. The fabricated MSCs demonstrate a capacitance of 1.3 μF/cm2 with an energy density of 0.42 μJ/cm2. Thus, utilization of a Ti diffusion barrier with a CMOS compatible Pd metal electrode is a step towards integrating MSCs in semiconductor microsystems.
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