AVS 60th International Symposium and Exhibition
    Graphene and Other 2D Materials Focus Topic Thursday Sessions
       Session GR+AS+BI+PS+SS-ThA

Paper GR+AS+BI+PS+SS-ThA8
Field Effect Control of Carrier Conduction in Helium Ion Irradiated Graphene

Thursday, October 31, 2013, 4:20 pm, Room 104 B

Session: Plasma Processing, Surface Chemistry, Functionalization, and Sensor Applications of 2D Materials
Presenter: S. Nakaharai, AIST, Japan
Authors: S. Nakaharai, AIST, Japan
T. Iijima, AIST, Japan
S. Ogawa, AIST, Japan
S.-L. Li, NIMS, Japan
K. Tsukagoshi, NIMS, Japan
S. Sato, AIST, Japan
N. Yokoyama, AIST, Japan
Correspondent: Click to Email
We demonstrate the gate control of carrier conduction in graphene which is functionalized by Helium ion beam irradiation in a Helium Ion Microscope (HIM) [1]. Carrier conduction control is important for graphene application to electronics, but it has long been an obstacle to realization of graphene electronics. We found that an appropriate amount of He ion dose to graphene induced point defects which enabled gate bias control of current with an on-off ratio of two orders of magnitude at room temperature.

Helium ions were applied to graphene with ion doses from 2.2x1015 ions/cm2 to 1.3x1016 ions/cm2. The induced defect density was estimated by numerical calculation to be 0.2% to 1.3% [2]. The introduction of defects was confirmed by the D-mode peak of Raman spectroscopy. A series of samples with different ion doses exhibited a drastic decay of current by more than five orders of magnitude as the defect density increased from 0.2% to 1.3%. In spite of such a drastic change in current, the basic structure of graphene remained, as evidenced by G-mode peak of the Raman spectra. Room temperature current switching with an on-off ratio of two orders of magnitude was realized at a moderate defect density of 0.9%. We also found that the current exhibited an exponential decay as the irradiated region length increased from 5 to 50 nm. These results suggest that the carriers in graphene are spatially localized due to interference of waves which are scattered at the randomly distributed defect sites. A theoretical investigation of localization in a defective graphene has predicted that 1% point defects will cause a strong localization of carriers [3], which shows good agreement with our experimental results. Therefore, it should be argued that the gate control of carrier conduction is realized by a transport gap which is generated by defect-induced localization.

Since the presented technique of graphene functionalization is a “top-down” process, it is easily introduced to the fabrication process of future electron devices. We will also present the application of our ion irradiation technique to the channel of graphene transistors [4] which achieved nearly four orders of magnitude on-off ratio at 250 K.

This research is granted by JSPS through FIRST Program initiated by CSTP.

References: [1] S. Nakaharai, et al., ACS Nano 7, 5694 (2013), [2] M. C. Lemme, et al., ACS Nano 3, 2674 (2009); D. Bell, et al., Nanotechnology 20, 455301 (2009), [3] A. Lhebier, et al., Phys. Rev. B 86, 075402 (2012). [4] S. Nakaharai, et al., IEEE Tech. Dig. IEDM2012, p.72 (2012).