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ALD growth of 10 nm Al2O3 at Tch = 80 °C on (a) HOPG and (b) CVD graphene after transfer on SiO2. SEM pictures taken in the same conditions at 3 kV.
ALD growth of Al2O3 at Tch = 80 °C on CVD graphene on Cu. (a) Large scale high quality monolayer graphene sheets grown on a Cu foil. Sample size is compared to a copper based 1 pence coin. SEM pictures taken in the same conditions at 3 kV after the growth of (b) 10 nm and (c) 3 nm of Al2O3. The red arrow points to a selected <10 nm wide crack.
(a) Process leading to well wetted Al2O3/graphene films on SiO2. (b) Mapping of the Raman D/G ratio (λ = 532 nm, ×100 optic, 0.6 μm spot diameter, and 1 μm steps) of the encapsulated graphene sheet in-between Al2O3 and SiO2 (c) Statistical analyses confirm that the D/G ratio is typically 0.05-0.06, similar to as grown graphene.
(a) Comparison of the coverage of the Al2O3 grown by ALD on different graphene-like materials and at different Tch (as observed through the SEM at ×100k magnification). Two trends clearly emerge. Low coverage: HOPG, monolayer graphene on SiO2 and graphene multilayers on Cu or Ni-Au; High coverage: monolayer graphene on Cu or Ni-Au. (b) Sketch of the trapping mechanism arising in the case of monolayer graphene/metal samples: water molecules are more efficiently adsorbed on the surface during the first ALD cycles and thus allow a more two dimensional Frank–van der Merwe growth of the Al2O3.
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