One‐Step Formation of a Single Atomic‐Layer Transistor by the Selective Fluorination of a Graphene Film

Abstract

In this study, the scalable and one-step fabrication of single atomic-layer transistors is demonstrated by the selective fluorination of graphene using a low-damage CF4 plasma treatment, where the generated F-radicals preferentially fluorinated the graphene at low temperature (<200 °C) while defect formation was suppressed by screening out the effect of ion damage. The chemical structure of the C-F bonds is well correlated with their optical and electrical properties in fluorinated graphene, as determined by X-ray photoelectron spectroscopy, Raman spectroscopy, and optical and electrical characterizations. The electrical conductivity of the resultant fluorinated graphene (F-graphene) was demonstrated to be in the range between 1.6 kΩ/sq and 1 MΩ/sq by adjusting the stoichiometric ratio of C/F in the range between 27.4 and 5.6, respectively. Moreover, a unique heterojunction structure of semi-metal/semiconductor/insulator can be directly formed in a single layer of graphene using a one-step fluorination process by introducing a Au thin-film as a buffer layer. With this heterojunction structure, it would be possible to fabricate transistors in a single graphene film via a one-step fluorination process, in which pristine graphene, partial F-graphene, and highly F-graphene serve as the source/drain contacts, the channel, and the channel isolation in a transistor, respectively. The demonstrated graphene transistor exhibits an on-off ratio above 10, which is 3-fold higher than that of devices made from pristine graphene. This efficient transistor fabrication method produces electrical heterojunctions of graphene over a large area and with selective patterning, providing the potential for the integration of electronics down to the single atomic-layer scale.

Fluorinated Graphene as High Performance Dielectric Materials and the Applications for Graphene Nanoelectronics

“…Specifically, a polymer nanowire mask was used to selectively expose graphene to ambient XeF 2 gas ambient27. Recently, we have successfully fabricated a unique semi-metal/semiconductor/insulator heterojunction structure directly using a single graphene sheet via a selective fluorination process28. This technique can potentially be used for the integration of electronics at the single atomic layer scale.…”

“…Herein, we present a novel graphene-based field effect transistor architecture in which fluorographene is introduced as the gate dielectric material. The CVD-grown graphene was fluorinated using a low-damaged CF 4 plasma treatment, which allows for its integration with IC fabrication to achieve large-area processing28. During this process, a filter is inserted between the CF 4 plasma and graphene sheet to reduce damage caused by high energy radicals and UV photons.…”

Role of defect states in functionalized graphene photodetectors

“…The absence of shift leads to two possible conclusions: firstly that FGr is transparent at these wavelength, or that there is absorption in FGr but limited charge transfer between graphene and FGr. The former can be eliminated as absorption measurements of FGr with a similar fluorine content (19%) demonstrated a band gap of 2.48 eV, [15] well below the photon energy used here (3.1 eV).…”

“…Furthermore, demonstration of nanoscale patterning of fluorinated graphene by electron beam irradiation allows for further miniaturization of optoelectronic devices. [12] The optical properties of fluorinated graphene have been widely investigated both experimentally, using absorption and photoluminescence spectroscopy, [13][14][15] and theoretically. [16] These works all indicate that the band gap of FGr can be tuned from the ultraviolet to near-infrared by controlling the degree of fluorination.…”

New routes to the functionalization patterning and manufacture of graphene-based materials for biomedical applications

“…For example, it has been shown that F-functionalized graphene can be prepared using F-based plasma treatments to provide a highly stable covalent bond of C2F [50 -52]. Furthermore, to achieve local fluorination, a patterned buffer layer during the CF 4 plasma treatment has been successfully demonstrated [53].…”