# Radio-Frequency Conductivity Characteristics and Corresponding Mechanism of Graphene/Copper Multilayer Structures

## TL;DR

This paper studies how graphene/copper multilayers behave under radio-frequency conditions and explains the mechanisms behind their conductivity.

## Contribution

The study reveals the RF conductivity mechanism and behavior of graphene/copper multilayers using SMIM and dielectric resonator techniques.

## Key findings

- Multilayer graphene/copper structures showed lower RF conductivity than pure copper at 3 GHz.
- Monolayer graphene/copper structures exhibited higher RF conductivity due to thermal effects increasing carrier concentration.
- Intrinsic defects in multilayer graphene caused additional carrier scattering, reducing RF conductivity.

## Abstract

High-radio-frequency (RF) conductivity is required in advanced electronic materials to reduce the electromagnetic loss and power dissipation of electronic devices. Graphene/copper (Gr/Cu) multilayers possess higher conductivity than silver under direct current conditions. However, their RF conductivity and detailed mechanisms have rarely been evaluated at the micro scale. In this work, the RF conductivity of copper–copper (P-Cu), monolayer-graphene/copper (S-Gr/Cu), and multilayer-graphene/copper (M-Gr/Cu) multilayer structures were evaluated using scanning microwave impedance microscopy (SMIM) and dielectric resonator technique. The results indicated that the order of RF conductivity was M-Gr/Cu < P-Cu < S-Gr/Cu at 3 GHz, contrasting with P-Cu < M-Gr/Cu < S-Gr/Cu at DC condition. Meanwhile, the same trend of M-Gr/Cu < P-Cu < S-Gr/Cu was also observed using the dielectric resonator technique. Based on the conductivity-related Drude model and scattering theory, we believe that the microwave radiation can induce a thermal effect at S-Gr/Cu interfaces, leading to an increasing carrier concentration in S-Gr. In contrast, the intrinsic defects in M-Gr introduce additional carrier scattering, thereby reducing the RF conductivity in M-Gr/Cu. Our research offers a practical foundation for investigating conductive materials under RF conditions.