| 1. |
- Boix, Virgínia, et al.
(författare)
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Area-selective Electron-beam induced deposition of Amorphous-BNx on graphene
- 2021
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332. ; 557, s. 149806-149806
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Tidskriftsartikel (refereegranskat)abstract
- Thin, stable and inert dielectric spacers are essential for manufacturing electronic devices based on 2D materials. However, direct synthesis on top of 2D materials is difficult due to their inert nature. In this work, we studied how an electron beam induces fragmentation of borazine and enables spatially confined synthesis of amorphous-BNx on graphene at room temperature. Using a combination of X-ray Photoelectron Spectroscopy, Low Energy Electron Microscopy, and Scanning Tunneling Microscopy we studied the morphology of the heterostructure, its chemical composition, and finally its temperature evolution. We find that electron-beam induced deposition starts by the binding of heavily fragmentized borazine, including atomic boron, followed by the growth of a multilayer with a 1:0.7 B:N ratio. The final structure exhibits a thermal stability up to 1400 K and ~ 50 nm spatial control provided by the electron beam. Our studies provide surface science insight into the use of electron beams for synthesis and lateral control of stable and inert layers in 2D heterostructures.
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| 2. |
- Bouhafs, Chamseddine, et al.
(författare)
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Synthesis of large-area rhombohedral few-layer graphene by chemical vapor deposition on copper
- 2021
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Ingår i: Carbon. - : Elsevier BV. - 0008-6223. ; 177, s. 282-290
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Tidskriftsartikel (refereegranskat)abstract
- Rhombohedral-stacked few-layer graphene (FLG) displays peculiar electronic properties that could lead to phenomena such as high-temperature superconductivity and magnetic ordering. To date, experimental studies have been mainly limited by the difficulty in isolating rhombohedral FLG with thickness exceeding 3 layers and device-compatible size. In this work, we demonstrate the synthesis and transfer of rhombohedral graphene with thickness up to 9 layers and areas up to ∼50 μm2. The domains of rhombohedral FLG are identified by Raman spectroscopy and are found to alternate with Bernal regions within the same crystal in a stripe-like configuration. Near-field nano-imaging further confirms the structural integrity of the respective stacking orders. Combined spectroscopic and microscopic analyses indicate that rhombohedral-stacking formation is strongly correlated to the underlying copper step-bunching and emerges as a consequence of interlayer displacement along preferential crystallographic orientations. The growth and transfer of rhombohedral FLG with the reported thickness and size shall facilitate the observation of predicted unconventional physics and ultimately add to its technological relevance.
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| 3. |
- Scardamaglia, Mattia, et al.
(författare)
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Comparative study of copper oxidation protection with graphene and hexagonal boron nitride
- 2021
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Ingår i: Carbon. - : Elsevier BV. - 0008-6223. ; 171, s. 610-617
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Tidskriftsartikel (refereegranskat)abstract
- The use of protective barriers to isolate a metal surface from an aggressive environment is a common way to inhibit its degradation. We used ambient pressure x-ray photoelectron spectroscopy to assess in real time the evolution of the copper surface and the contextual protective action of 2D material coatings (graphene and hexagonal boron nitride) towards copper oxidation. In an isobaric experiment with 2 mbar of oxygen, the bare copper oxidizes near room temperature, while both 2D materials can retard the onset temperature for the first oxidation of copper by more than 120 °C. However, their protection mechanism is different: boron nitride behaves more straightforwardly, forming an effective barrier to copper oxidation until it is etched away at high temperatures, leading to a rapid oxidation to cuprous and then cupric oxide. On the other hand, graphene reveals to be a more interesting playground underneath oxygen intercalates and begins a slower undercover oxidation of copper. The coexistence between graphene and cuprous oxide, not observed in boron nitride, protects the copper from further oxidation to cupric oxide.
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