On the local conductivity of individual diamond seeds and their impact on the interfacial resistance of boron-doped diamond films

In many electroanalytical and bio-electrochemical applications conductive diamond films act as contact layers. These films are grown starting from a Si-surface seeded with undoped diamond particles. In this study, the impact of the seeds and their electrical properties on the interfacial resistance through the diamond film − substrate is determined on the nanometer-scale by probing the nucleation side of the conductive diamond films using scanning spreading resistance microscopy. We evidence that, although the diamond film is grown in a B-rich ambient, no significant B incorporation occurs into the particles and they remain non-conductive after growth. We demonstrate that they impact strongly on the interfacial resistance, increasing it by more than one order of magnitude depending on the seed layer coverage. We further establish a model linking the seed size and density to this interfacial resistance, with excellent agreement to our experimental results. Based on this model, we predict that it is necessary to limit the undoped particle density to less than 5 × 1010 cm−2, for 20 nm particle size, in order to eliminate the contribution of the undoped seeds to the interfacial resistance. Our model also indicates that the fundamental solution to this problem lies in the use of B-doped seeds.