The enhanced growth of Cu oxides underneath graphene
grown on a
Cu substrate has been of great interest to many groups. In this work,
the strain and doping status of graphene, based on the gradual growth
of Cu oxides from underneath, were systematically studied using time
evolution Raman spectroscopy. The compressive strain to graphene,
due to the thermal expansion coefficient difference between graphene
and the Cu substrate, was almost released by the nonuniform Cu2O growth; however, slight tensile strain was exerted. This
induced p-doping in the graphene with a carrier density up to 1.7
× 1013 cm–2 when it was exposed
to air for up to 30 days. With longer exposure to ambient conditions
(>1 year), we observed that graphene/Cu2O hybrid structures
significantly slow down the oxidation compared to that using a bare
Cu substrate. The thickness of the CuO layer on the bare Cu substrate
was increased to approximately 270 nm. These findings were confirmed
through white light interference measurements and scanning electron
microscopy.
2D heterostructures made of transition metal dichalcogenides (TMD) have emerged as potential building blocks for new‐generation 2D electronics due to their interesting physical properties at the interfaces. The bandgap, work function, and optical constants are composition dependent, and the spectrum of applications can be expanded by producing alloy‐based heterostructures. Herein, the successful synthesis of monolayer and bilayer lateral heterostructures, based on ternary alloys of MoS2(1−x)Se2x–WS2(1−x)Se2x, is reported by modifying the ratio of the source precursors; the bandgaps of both materials in the heterostructure are continuously tuned in the entire range of chalcogen compositions. Raman and photoluminescence (PL) spatial maps show good intradomain composition homogeneity. Kelvin probe measurements in different heterostructures reveal composition‐dependent band alignments, which can further be affected by unintentional electronic doping during the growth. The fabrication of sequential multijunction lateral heterostructures with three layers of thickness, composed of quaternary and ternary alloys, is also reported. These results greatly expand the available tools kit for optoelectronic applications in the 2D realm.
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