This disclosure relates to a transmission line for high performance radio frequency (RF) applications. One such transmission line can include a bonding layer configured to receive an RF signal, a barrier layer, a diffusion barrier layer, and a conductive layer proximate to the diffusion barrier layer. The diffusion barrier layer can have a thickness that allows a received RF signal to penetrate the diffusion barrier layer to the conductive layer. In certain implementations, the diffusion barrier layer can be nickel. In some of these implementations, the transmission line can include a gold bonding layer, a palladium barrier layer, and a nickel diffusion barrier layer.