Synthesis of Few-Layer and Multi-Layer Graphene and Fabrication of Top-Gated Field Effect Transistors without Using Tran
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1205-L03-24
Synthesis of Few-Layer and Multi-Layer Graphene and Fabrication of Top-Gated Field Effect Transistors without Using Transferring Processes Daiyu Kondo1,2,3, Katsunori Yagi1, Naoki Harada1, Motonobu Sato1,2,3, Mizuhisa Nihei1,2,3, Shintaro Sato1,2,3, Naoki Yokoyama1 1
Nanoelectronics Research Center, Fujitsu Laboratories Ltd., 10-1 Mirinosato-Wakamiya, Atsugi, Kanagawa 243-0197, Japan 2 Fujitsu Limited, 10-1 Mirinosato-Wakamiya, Atsugi, Kanagawa 243-0197, Japan. 3 CREST-JST, 10-1 Mirinosato-Wakamiya, Atsugi, Kanagawa 243-0197, Japan.
ABSTRACT We have fabricated top-gated field effect transistors (FETs) using graphene synthesized by chemical vapor deposition directly on a SiO2/Si substrate without using any transferring processes. Graphene was synthesized on an Fe catalyst film on the substrate at 650ºC. The catalyst film was then etched after both ends of the graphene were fixed by source and drain electrodes, leaving the graphene channel connecting the two electrodes. Top-gated FETs were then made by covering graphene channels with HfO2 and depositing top electrodes. The drain current was successfully modulated by the gate voltage and exhibited the ambipolar behavior that is characteristic of graphene. Also, it has been shown that graphene channels can sustain an electric current with a density of 107–108 /cm2. Our newly developed fabrication process paves a way to fabricate graphene transistors all over large substrates including Si and glass.
INTRODUCTION Graphene has been attracting much attention since single-layer graphene was first separated in 2004 [1]. It has unique electronic properties arising from its linear energy dispersion characterstics. For instance, an extraordinary high electrical mobility of 200,000 cm2/Vs has been reported [2]. Graphene also has excellent mechanical and thermal properties [3,4]. These properties, along with its planar structure, make graphene promising a material for future nanoelectronics. One of the promising applications of graphene is a field effect transistor (FET). Many studies using exfoliated graphene as a transistor channel have been reported [5-7]. However, for real-world applications, use of exfoliated graphene is not realistic. In light of this, synthesis of graphene by chemical vapor deposition (CVD) on a substrate has been attempted [8-10]. In these studies, graphene was formed on a metal catalyst film (Ni or Cu), and transferred to another substrate for electrical measurements. The source gas of CVD was mainly CH4 and the growth temperature was 800–1000ºC. These studies are an important step toward realizing graphenebased electronics. However, the transferring process may not be appropriate for applications using a large substrate, including LSI applications. We believe that we need to form a graphene channel directly on a desired substrate without using such a transferring process.
Here we propose a novel method to grow graphene and fabricate transistors directly on a desired insulating substrate without using any transferring processes. In this
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