The graphene coplanar waveguide (CPW) has recently been found to have large insertion loss (typically larger than 50 dB/100 μm), which mainly results from the large resistance of graphene. The poor radio-frequency transmission property of graphene hampers its application in interconnect, a low loss material is thus required. In this paper, low-resistance graphite CPWs with effective graphite length up to 200 μm were fabricated. A record low insertion loss of graphite CPW (2.76 dB/100 μm) is demonstrated, and the average insertion loss of our graphite CPWs is only ∼1/5 of that of our monolayer graphene CPWs. Moreover, we find the insertion loss of graphite CPW may be even smaller at higher frequencies. Our investigation shows that graphite is a possible candidate for interconnect and may even be more applicable at ultra-high frequencies.

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In this paper, we focus on the influence of series resistance of signal line (comoprised of the sheet resistance of graphene and the contact resistance between graphene and metal) on the radio-frequency transmission property of graphene coplanar waveguide (CPW) and put forward ways to improve it. According to our research, the large series resistance (7.2 kΩ) of signal line is the main reason for the large insertion loss (|S 21 |) of graphene CPW. The insertion loss of graphene CPW is found to be reduced by either enlarging the area of graphene-metal contact or increasing the number of graphene layers.