We present a comprehensive study of the structural and electronic properties of ultrathin films containing graphene layers synthesized by chemical vapor deposition based surface segregation on polycrystalline Ni foils then transferred onto insulating SiO2/Si substrates. Films of size up to several mm's have been synthesized. Structural characterizations by atomic force microscopy, scanning tunneling microscopy, cross-sectional transmission electron microscopy (XTEM), and Raman spectroscopy confirm that such large-scale graphitic thin films (GTF) contain both thick graphite regions and thin regions of few-layer graphene. The films also contain many wrinkles, with sharply-bent tips and dislocations revealed by XTEM, yielding insights on the growth and buckling processes of the GTF. Measurements on mm-scale back-gated transistor devices fabricated from the transferred GTF show ambipolar field effect with resistance modulation ∼50% and carrier mobilities reaching ∼2000 cm 2/V s. We also demonstrate quantum transport of carriers with phase coherence length over 0.2 μm from the observation of two-dimensional weak localization in low temperature magnetotransport measurements. Our results show that despite the nonuniformity and surface roughness, such large-scale, flexible thin films can have electronic properties promising for device applications.
Bibliographical noteFunding Information:
YPC acknowledges support from Miller Family Endowment, Birck Director’s Fund and Semiconductor Research Corporation (SRC)’s Nanoelectronics Research Initiative (NRI) via Midwest Institute for Nanoelectronics Discovery (MIND). HC acknowledges support from Grodzins endowment. Acknowledgment is also made to the donors of the American Chemical Society Petroleum Research Fund for partial support of this research. QY acknowledges support by NSF (under Grant No. 0620906) and CAM Special Funding. A portion of this work was carried out at the National High Magnetic Field Laboratory, which is supported by NSF Cooperative Agreement No. DMR-0084173, by the State of Florida and DOE. We thank Jun-Hyun Park and Eric Palm for experimental assistance. We also thank Xi Chen and Ron Reifenberger for helpful discussions.
ASJC Scopus subject areas
- General Physics and Astronomy