Ion implantation enables synthesis of layer-tunable graphene

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The journal’s back cover features a schematic of the ion implantation process. The method uses ion implantation to introduce a precise dose of carbon atoms (the implanted carbon atoms are depicted as meteors) into the top nickel layer of the nickel/copper bilayer substrate at room temperature (blue depicts nickel atoms and green depicts copper atoms). The implanted carbon ion acts as a carbon reservoir for subsequent synthesis of graphene. Implanted carbon atoms are gradually expelled to the surface and transformed into graphene due to the extremely low solubility of carbon in copper.

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A new layer-tunable graphene synthesis method, developed in part at LANL’s Ion Beam Materials Laboratory, has the potential to be used in large-scale production lines and speed the application of graphene in nanoelectronics. Advanced Functional Materials published the research and featured a figure from the work on the back cover.

Graphene, a strip of pure carbon one atom thick, is stronger than steel and is an outstanding conductor of electricity and heat. Incorporating this material into real-world applications has proved challenging because the common production method, chemical vapor disposition, is cumbersome, expensive, and toxic. The authors report an ion implantation method that is simpler and offers precise control of graphene thickness, a crucial experimental parameter related to the physicochemical properties of graphene. 

Yongqiang Wang (Materials Science in Radiation and Dynamics Extremes, MST-8) used an ion implanter at the Lab’s Ion Beam Materials Laboratory to insert the required number of carbon atoms to form single-layer and double-layer graphene on a copper-nickel substrate. Selection of specific ion energy and fluence enables ion implantation to deliver the exact number of foreign atoms at a precise location within the host material matrix (Figure 8). Implanted carbon atoms expelled during the growth process produce high-quality graphene with the desired number of layers, typically single or double layers. Theoretical calculations confirmed the growth mechanism. This is the first investigation of the use of a dual metal substrate combined with ion implantation for the synthesis of layer-tunable graphene. Because ion implantation is a core technology in microelectronics processing, this method could be implemented into production lines and to expedite the application of graphene to nanoelectronics.

Reference: “Synthesis of Layer-Tunable Graphene: A Combined Kinetic Implantation and Thermal Ejection Approach,” Advanced Functional Materials 25, 3666(2015), doi: SScciieenncceeHHiigghhlliigghhttss((0088--0055--1155))LALP 15-001 16 10.1002/adfm.201500981. Authors: Yongqiang Wang (MST-8) and researchers from the Chinese Academy of Sciences, Lanzhou University, City University of Hong Kong, Shanghai University, East China Normal University, and University at Buffalo - State University of New York.

The Center of Integrated Nanotechnologies (CINT), a DOE nanoscience user program jointly operated by Los Alamos and Sandia national laboratories, provided partial support. The Ion Beam Materials Laboratory is a multi-user research facility with multiple sponsors [DOE Basic Energy Sciences, DOE Nuclear Energy, Laboratory Directed Research and Development (LDRD) program, and the University of California Lab fee research]. The work supports the Laboratory’s Energy Security mission area and Materials for the Future science pillar via advancement of the science to develop materials with properties optimized for specific functions and applications, such as nanoelectronics. Technical contact: Yongqiang Wang

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Schematic of the synthesis process to produce single-­‐layer and double-­‐layer graphene by ion implantation. Nickel (Ni) is depicted as green spheres, carbon (C) as blue, and copper (Cu) as yellow. Carbon ions with the predesigned fluence were implanted into the top nickel layer of the Ni/Cu bilayer substrate followed by annealing. The thermal process initiates interdiffusion of Cu atoms and Ni atoms to form the Cu-­‐like alloy. Carbon atoms are expelled from the Cu-­‐like alloy toward the surface, and graphene with the expected layer number is formed on the surface.