Selective growth of graphene by chemical vapor deposition on Cu-Ni alloy patterns

Time 2018-11-08 15:30~15:55 Place Rm. 600A
Code No. MD-O01 Session Chair
Name Prof. Hyung Gyu Park, Dr. Kyung Jun Choi
Affiliation ETH Zurich
Title Selective growth of graphene by chemical vapor deposition on Cu-Ni alloy patterns
Contents
Improving the properties of graphene has been intensively investigated to facilitate the practical applications for electronics. However, it is still demanding to conceive a novel approach for lowering the growth temperature, reducing the growth time, and simplifying the patterning steps. Because post- fabrication processes such as e-beam lithography or photolithography could cause contaminations by polymer residue or structural and chemical alterations, the otherwise exceptional properties of graphene often suffer from degradation. We report a simple method to prepare uniformly and selectively grown monolayer graphene by means of chemical vapor deposition and of a synergetic effect between Cu-Ni alloy and acetylene carbon feedstock. In order to achieve a low growth temperature and a short growth time, we systemically optimize the growth condition by controlling a Ni concentration on Cu surface and the acetylene partial pressure. The results show that a pre- patterned Cu-Ni alloy with low acetylene partial pressure allow the synthesis of high-quality and uniform monolayer graphene at low temperature (800 °C), evidenced by electron microscopies, Raman spectroscopy, and electronics characterization. Furthermore, observation of time-dependent activation energy (2.77 eV) of graphene formation on the Cu catalyst that follows Gompertzian kinetics suggests that the rate-determining step may be the catalytic decomposition of acetylene, creating a time lag to synthesize graphene between Cu-Ni alloy and Cu. This difference in growth kinetics is crucial to selective growth. Organic field-effect transistors based on the selectively grown graphene electrodes exhibited enhanced performance compared with photolithography-patterned graphene electrodes. We expect that our method of the pre-patterned growth could permit the cost- effective high-performance synthesis of graphene, as well as their applications, through provision of intermediate synthesis temperature and simplification of the otherwise complicated post-growth pattering of graphene electrodes.