Daesung Jung

Soft Lithography of Graphene Sheets Via Surface Energy Modification

A simple and efficient soft lithographic process for an easily applicable patterning method for large-scale graphene sheets was demonstrated. The surface of an elastomeric stamp was functionalized with polar molecules to enhance the interfacial adhesive force between the stamp and the graphene layer. A specific graphene area was then patterned on the initial substrate and transferred to the target surface by contacting with the stamp.

Fabrication of Graphene p-n Junction Field Effect Transistors on Patterned Self-Assembled Monolayers/Substrate

The field-effect transistors (FETs) with a graphene-based p-n junction channel were fabricated using the patterned self-assembled monolayers (SAMs). The self-assembled 3-aminopropyltriethoxysilane (APTES) monolayer deposited on SiO₂/Si substrate was patterned by hydrogen plasma using selective coating poly-methylmethacrylate (PMMA) as mask. The APTES-SAMS on the SiO₂ surface were patterned using selective coating of PMMA. The APTES-SAMs of the region uncovered with PMMA was removed by hydrogen plasma. The graphene synthesized by thermal chemical vapor deposition was transferred onto the patterned APTES-SAM/SiO₂ substrate. Both p-type and n-type graphene on the patterned SAM/SiO₂ substrate were fabricated. The graphene-based p-n junction was studied using Raman spectroscopy and X-ray photoelectron spectroscopy. To implement low voltage operation device, via ionic liquid (BmimPF 6 ) gate dielectric material, graphene-based p-n junction field effect transistors was fabricated, showing two significant separated Dirac points as a signature for formation of a p-n junction in the graphene channel.

Direct Growth of Graphene on Insulating Substrate by Laminated (Au/Ni) Catalyst Layer

A direct growth method of graphene on insulating substrate without catalyst etching and transfer process was developed using Au/Ni/a-C catalyst system. During the growth process, behavior of the Au/Ni catalyst was investigated using EDX, XPS, SEM, and Raman spectroscopy. The Au/Ni catalyst layer was evaporated during growth process of graphene. The graphene film was composed mono-layer flakes. The transmittance of the graphene film was ∼80.6%.