균일하고 0 V에 가까운 Dirac 전압을 갖는 그래핀 전계효과 트랜지스터 제작 공정
Fabrication of Graphene Field-effect Transistors with Uniform Dirac Voltage Close to Zero
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초록
Monolayer graphene grown via chemical vapor deposition (CVD) is recognized as a promising material for sensor applications owing to its extremely large surface-to-volume ratio and outstanding electrical properties, as well as the fact that it can be easily transferred onto arbitrary substrates on a large-scale. However, the Dirac voltage of CVD-graphene devices fabricated with transferred graphenelayers typically exhibit positive shifts arising from transfer and photolithography residues on the graphene surface. Furthermore, theDirac voltage is dependent on the channel lengths because of the effect of metal-graphene contacts. Thus, large and nonuniform Diracvoltage of the transferred graphene is a critical issue in the fabrication of graphene-based sensor devices. In this work, we propose afabrication process for graphene field-effect transistors with Dirac voltages close to zero. A vacuum annealing process at 300 °C was performed to eliminate the positive shift and channel-length-dependence of the Dirac voltage. In addition, the annealing process improved the carrier mobility of electrons and holes significantly by removing the residues on the graphene layer and reducing the effect of metal-graphene contacts. Uniform and close to zero Dirac voltage is crucial for the uniformity and low-power/voltage operation for sensor applications. Thus, the current study is expected to contribute significantly to the development of graphene-based practical sensordevices.
Abstract
Monolayer graphene grown via chemical vapor deposition (CVD) is recognized as a promising material for sensor applications owing to its extremely large surface-to-volume ratio and outstanding electrical properties, as well as the fact that it can be easily transferred onto arbitrary substrates on a large-scale. However, the Dirac voltage of CVD-graphene devices fabricated with transferred graphenelayers typically exhibit positive shifts arising from transfer and photolithography residues on the graphene surface. Furthermore, theDirac voltage is dependent on the channel lengths because of the effect of metal-graphene contacts. Thus, large and nonuniform Diracvoltage of the transferred graphene is a critical issue in the fabrication of graphene-based sensor devices. In this work, we propose afabrication process for graphene field-effect transistors with Dirac voltages close to zero. A vacuum annealing process at 300 °C was performed to eliminate the positive shift and channel-length-dependence of the Dirac voltage. In addition, the annealing process improved the carrier mobility of electrons and holes significantly by removing the residues on the graphene layer and reducing the effect of metal-graphene contacts. Uniform and close to zero Dirac voltage is crucial for the uniformity and low-power/voltage operation for sensor applications. Thus, the current study is expected to contribute significantly to the development of graphene-based practical sensordevices.
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