Thermal and Electrical Conductivity of Copper-Graphene Heterosystem: An Effect of Strain and Thickness

Abstract

Copper-graphene (Cu/Gr) composite carries high thermal (κ) and electrical (σ) conductivities compared with pristine copper film/surface. For further improvement, strain is applied (compressive and tensile) and thickness is changed (of both copper and graphene). It is observed that electronic thermal conductivity (κe) and σ enhance from 320.72 to 869.765 W mK−1 and 5.28 × 107 to 23.01 × 107S m−1, respectively, by applying 0.20% compressive strain. With the increase in copper thickness (three to seven layers) in Cu(111)/single-layer-graphene (SLG) heterosystem, κe increases from 320.72 to 571.81 W mK−1 while electrical resistivity (ρ ∝ (1/σ)) decreases from 0.189 × 10−7 to 0.117 × 10−7Ωm. Furthermore, with the increase in graphene thickness (one to four layers) in seven-layer Cu(111)/multilayer-graphene (MLG) heterosystem, κe enhances upto 126% while ρ decreases upto 70% compared with the three-layer Cu(111)/SLG. A large available state near Fermi level (of Cu/Gr heterosystem) offers the conduction of more electrons from valence to conduction bands. The increasing thickness broadens this state and enhances conduction electrons. The electron localization function decreases with increasing thickness, suggesting electrons are delocalized at copper-graphene junction, resulting in an increase of free electrons that enhance κe and σ. Herein, it is useful in advancing the thermal management of electronic chips and in applying hybrid copper-graphene interconnects.