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In situ atomic-level studies of Gd atom release and migration on graphene from a metallofullerene precursor

DOI: 10.1021/acsnano.8b06057 DOI Help

Authors: Sapna Sinha (University of Oxford) , Yuewen Sheng (University of Oxford) , Ian Griffiths (University of Oxford) , Neil P. Young (University of Oxford) , Si Zhou (University of Oxford) , Angus I. Kirkland (University of Oxford; Diamond Light Source) , Kyriakos Porfyrakis (University of Oxford) , Jamie H. Warner (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acs Nano

State: Published (Approved)
Published: September 2018

Abstract: We show how gadolinium (Gd)-based metallofullerene (Gd3N@C80) molecules can be used to create single adatoms and nanoclusters on a graphene surface. An in situ heating holder within an aberration-corrected scanning transmission electron microscope is used to track the adhesion of endohedral metallofullerenes (MFs) to the surface of graphene, followed by Gd metal ejection and diffusion across the surface. Heating to 900 °C is used to promote adatom migration and metal nanocluster formation, enabling direct imaging of the assembly of nanoclusters of Gd. We show that hydrogen can be used to reduce the temperature of MF fragmentation and metal ejection, enabling Gd nanocluster formation on graphene surfaces at temperatures as low as 300 °C. The process of MF fragmentation and metal ejection is captured in situ and reveals that after metal release, the C80 cage opens further and fuses with the surface monolayer carbon glass on graphene, creating a highly stable carbon layer for further Gd adatom adhesion. Small voids and defects (∼1 nm) in the surface carbon glass act as trapping sites for Gd atoms, leading to atomic self-assembly of 2D monolayer Gd clusters. These results show that MFs can adhere to graphene surfaces at temperatures well above their bulk sublimation point, indicating that the surface bound MFs have strong adhesion to dangling bonds on graphene surfaces. The ability to create dispersed single Gd adatoms and Gd nanoclusters on graphene may have impact in spintronics and magnetism.

Journal Keywords: annular dark-field scanning transmission electron microscopy; gadolinium; graphene; metallofullerenes; transmission electron microscopy; two-dimensional materials

Subject Areas: Materials, Chemistry

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