This thesis utilises X-ray photoelectron spectroscopy (XPS) to investigate the chemical interactions of Ru and Mn based Cu diffusion barrier layer structures with dielectric substrates with a view to incorporating these materials into future generations of interconnect technology. The current barrier layer arrangement of Ta/TaN will imminently fail to meet the demanding requirements associated with aggressive device miniaturization. The first part of the thesis investigates the incorporation of manganese into a 3 nm Ru thin-film as a potential mechanism to improve its performance as a copper diffusion barrier/liner combination layer. Mn and Al (~1 nm) were deposited in separate studies on an atomic layer deposited (ALD) Ru film and the Metal/Ru/SiO2 structures were subsequently thermally annealed. XPS studies revealed the chemical interaction of both Mn and Al with the SiO2 substrate to form MnSiO3 and Al2O3 respectively, implying the migration of both metals through the Ru film. Electron energy loss spectroscopy (EELS) line profile measurements of the intensity of the Mn signal across the Ru film confirm the presence of Mn at the Ru/SiO2 interface. In addition, secondary ion mass spectroscopy (SIMS) studies suggest the release and upward diffusion of Si from the SiO2 dielectric substrate formed as a result of Mn-silicate formation at the Ru/SiO2 interface. The second part of the thesis provides direct experimental evidence of the catalytic activity of bimetallic Ru/Mn surfaces towards oxygen and determines how this activity impacts upon the thermodynamic stability of Ru/Mn based Cu diffusion barrier layers. XPS analysis showed the thermal dissociation of Mn-based barrier layers and the desorption of O in the presence of Ru at lower temperatures than in systems without Ru present. Finally, XPS analysis of Ru/Mn on industrially relevant dielectric materials with varying carbon content and porosity is presented, along with the reduction of surface C concentration through exposure to atomic O.