We study the adhesion and tensile behaviour of bi-layer interfaces comprising polyethylene, doped with carbonyl and hydroxyl functional groups emanating from ozone treatment, and - by means of density functional theory and classical atomistic modelling. The results show that the deformations are localized within the polymer and comprise chain slip, disentanglement and detachment from the substrate, where only the latter is notably affected by the doping. The binding energies and excess forces associated with the detachment of functional groups from the alumina substrate are of the order of 1.7 eV and 1 nN, respectively, for both types. Although such forces do not affect the maximum peak stress notably, they give rise to spikes in the traction-separation curves following the fibril formation and promote increased total work of fracture.