Abstract
Developing an alternative method for fabricating microscale graphene patterns that overcomes the obstacles of organic contamination, linewidth resolution, and substrate damaging is paramount for applications in optoelectronics. Here we propose to pattern chemical vapor deposition grown graphene film through a stencil mask by magnetic-assisted ultraviolet (UV) ozonation under irradiation of a xenon excimer lamp. In this process, the paramagnetic oxygen molecules and photochemically generated oxygen radicals are magnetized and attracted in an inhomogenous external magnetic field. As a consequence, their random motions convert into directional, which can greatly modify or enhance the quality of graphene patterns. Using a ferromagnetic steel mask, an approximately vertical magnetic-field-assisted UV ozonation (BZ = 0.31 T, ∇BZ = 90 T · m−1) has a capability of patterning graphene microstructures with a line width of 29 μm and lateral under-oxidation less than 4 μm. Our approach is applicable to patterning graphene field-effect transistor arrays, and it can be a promising solution toward resist-free, substrate non-damaging, and cost effective microscale patterning of graphene film.
Highlights
MethodsA “PMMA-mediated” approach was used to transfer chemical vapor deposition (CVD) grown monolayer graphene on a copper foil onto the thermally grown SiO2 film (300 nm) on a highly doped p-type silicon substrate (0.001~0.004 ohm · cm) as follows[33,39,40]
We propose to pattern chemical vapor deposition (CVD) grown graphene film through stencil masks by magnetic-assisted UV ozonation
Ozonation vacuum machine is used for graphene patterning with a xenon excimer lamp installed on top inside the chamber (Supplementary Figure 1)
Summary
A “PMMA-mediated” approach was used to transfer CVD grown monolayer graphene on a copper foil onto the thermally grown SiO2 film (300 nm) on a highly doped p-type silicon substrate (0.001~0.004 ohm · cm) as follows[33,39,40]. We removed the copper foil in an etchant of 0.5 M FeCl3 aqueous solution after 3 h immersion and obtained the PMMA/graphene stack layer. The stack was etched by dipping in H2O/H2O2/HCl (20:1:1) and H2O/ H2O2/NH4OH (20:1:1) solutions successively to remove possible metal residues. After each etching, it was rinsed sufficiently by deionized water and scooped out onto a clean SiO2/Si substrate.
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