Spectroscopic properties of close-to-perfect-monolayer quasi-free-standing epitaxial graphene on 6H SiC(0001)

Dobrowolski, Artur; Jagiełło, Jakub; Piętak-Jurczak, Karolina; Wzorek, Marek; Czołak, Dariusz; Ciuk, Tymoteusz

doi:10.1016/j.apsusc.2023.158617

Cited by 3 publications

(3 citation statements)

References 43 publications

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“…Directly after the process, the material was electrically verified at room temperature using an Ecopia HMS-3000 direct-current Hall effect system. The measurements proved that the QFS graphene is p-type ,, and characterized by hole density of 7.1 × 10 12 cm –2 and hole mobility of 3619 cm 2 /(V s), in full accordance with the theory and our historical experience. ,, The substrate was diced into several 7.5 × 7.5 mm individual samples to guarantee a possibly high uniformity of the QFS graphene and the 6H-SiC(0001) substrate properties.…”

Section: Methodssupporting

confidence: 74%

“…The hydrogen-intercalated QFS graphene , (branded GET) was grown at 1600 °C on a semi-insulating vanadium-compensated nominally on-axis 15 mm × 15 mm 6H-SiC(0001) substrate (II–VI Inc.) through epitaxial CVD in the hot-wall Epigress VP508 reactor with propane as a carbon source . The in situ intercalation with hydrogen atoms took place at 1000 °C in a 900 mbar argon atmosphere.…”

Section: Methodsmentioning

confidence: 99%

“…The refractive indices n of the individual sublayers of the ALD a-Al 2 O 3 were determined with an Accurion EP4SE spectral imaging ellipsometer. 25 μm × 25 μm 2295-pixel mapping measurements were carried out in a nulling regime at a fixed angle of incidence (AOI) of 49° and wavelength λ = 490 nm, previously identified as optimum for this material composition . A beam-cutter was used to minimize the backside reflections.…”

Section: Methodsmentioning

confidence: 99%

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Origin of the Double Polarization Mechanism in Aluminum-Oxide-passivated Quasi-free-standing Epitaxial Graphene on 6H-SiC(0001)

Piętak-Jurczak,

Gaca,

Dobrowolski

et al. 2024

ACS Appl. Electron. Mater.

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In this work, we synthesize a 43 nm thick layer of amorphous Al 2 O 3 on transfer-free p-type hydrogen-intercalated quasi-free-standing (QFS) epitaxial chemical vapor deposition graphene on semi-insulating vanadium-compensated on-axis 6H-SiC(0001), using trimethylaluminum as the source of aluminum and deionized water or oxygen plasma as the source of oxygen. With a combination of surface-sensitive X-ray reflectometry (angular range of 0−6°), spectroscopic ellipsometry (angle of incidence of 49°and λ = 490 nm), and scanning transmission electron microscopy combined with energy-dispersive X-ray spectroscopy, we draw depth profiles of the physical density, refractive index, and elemental composition to reveal that the physical properties of the oxide are inhomogeneous. Its density increases from the graphene interface (ρ = ∼1.5 g/cm 3 ) toward the surface (ρ = ∼3.0 g/cm 3 ). Characteristically, it takes 26 nm for the oxide density to equal its reference value on a test silicon substrate. We demonstrate that an additional postdeposition annealing step in an oxygen-radical-reach environment densifies the oxide and elevates its oxygen content, thus suggesting that the a-Al 2 O 3 is oxygen deficient. We reason that the structural inhomogeneity induces the negative polarization effect and the associated reduction of intrinsic hole density observed in a-Al 2 O 3passivated p-type QFS graphene on hexagonal SiC(0001).

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