On the route to produce conductive Ni-related color centers in CVD-grown diamond

This paper focuses on the development of procedures able to provide multifunctional optical and electrical properties to polycrystalline diamond layers synthetized on silicon substrates. By exploiting the HF-CVD technique and the Si-Ni chemistry promoted by the presence of Ni during diamond growth, Si and Si-Ni defects acting as both color centers and free charge carriers were inserted into diamond lattice. To clarify the role played by the metal in modulating photoluminescence (PL) and charge transport, the Ni source is supplied either by drop-casting of NiCl2 solutions or by sputtering of Ni targets. A deep investigation of structure and emitting features of the produced samples is achieved by SEM, Raman spectroscopy, XPS, XRD and PL analyses, while the electrical behavior is pointed out by I-V and Hall effect measurements. The study allows for optimizing the state and amount of the Ni source able to give reliable functional features to the final materials, whereas preserving the structural integrity of the hosting diamond lattice. The collected results are evidence that the proposed synthesis approach enables the production of diamond-based systems showing a PL characterized by multiple emission lines and a significant conductivity suitable for assembling multifunctional devices working at room temperature.