This disclosure relates to a radio frequency (RF) transmission line for high performance RF applications. The RF transmission line includes a bonding layer having a bonding surface and configured to receive an RF signal, a barrier layer proximate the bonding layer, a diffusion barrier layer proximate the bonding layer and configured to prevent contaminant from entering the bonding layer, and a conductive layer proximate the diffusion barrier layer. The diffusion barrier layer has a thickness that allows the received RF signal to penetrate the diffusion barrier layer to the conductive layer. The diffusion barrier layer can be a nickel layer.