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(a) Schematic drawing of back gated graphene transistors used in this study. (b) Time trace of the temperature of rapid thermal annealing process. (c)Transfer curves of transistors with a channel length of 2 μm and a channel width of 100 μm, before and after the RTA process. These curves are the average of ∼30 devices. The drain voltage is −1 V and the transistor uses Ag electrodes. (d) Histogram of drain current before and after the RTA process for devices with 2 μm channel length. The improvement in the drain current is significantly larger than the variation of drain current. (e) The Raman spectra of graphene before and after RTA annealing in forming gas (5% H2 in N2) (f)Transfer curves of transistors with various channel lengths between 2 μm and 64 μm. (g) Scaling of drain current as function of the channel length before and after the RTA process. The improvement of drain current decreases with the channel length indicating that the RTA improves the contact resistance.
(a) Scaling of the total resistance of the graphene transistors as a function of channel length, before and after the RTA. The intersection point and the slope provide the contact resistance and the sheet resistance, respectively. Gate voltage dependence of the extracted contact resistance (b), and the sheet resistance (c), before and after the RTA. (d) Scaling of on-off ratio as a function of channel length.
(a) Effect of the RTA temperature on the tranfer curves of a transistor with a channel length of 4 μm and the channel width of 100 μm. The RTA time is 1 min. (b) The extracted sheet resistance of the graphene before and after RTA process for pure nitrogen gas and forming gas.
Extracted contact resistance of graphene for different contact metals; Cu, Ag, Au, and Pd. The inset shows the scaling of the total resistance of transistors with a channel width of 100 μm for Cu and Pd contacts.
(a) and (b) Variation of contact resistance (RcW) and sheet resistance (Rs ) with the gate voltage, respectively. (c) Channel length scaling of on-off ratio for various contact metals.
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