Electronic properties of boron and nitrogen co-doped nanocrystalline diamond

We investigated the structural and electronic properties of boron- and nitrogen-codoped nanocrystalline diamond (BNDD) films deposited via microwave plasma-enhanced chemical vapour deposition (MW PE CVD), systematically varying the nitrogen concentration from 0% to 2% N2 Vol% in the total gas flow. Introducing a low level of nitrogen (≤0.5%) resulted in a deterioration of crystallinity and an increase in growth rate. However, at higher concentrations (≥1%), the faceted structure was restored, and improved crystallinity was observed, accompanied by a slower growth rate. The concentration of both boron and nitrogen dopants within the films increased simultaneously up to 1% N2, suggesting an enhanced co-solubility of the dopants. All BNDD films showed p-type conductivity and exhibited metallic-like behaviour, as evidenced by the weak temperature dependence of conductivity, carrier concentration, and mobility. Electrical transport within the BNDD films is mainly influenced by boron acceptors, whereas nitrogen primarily serves as a compensating and scattering centre rather than an active donor. The results provide insight into how nitrogen modifies boron-dominated electronic transport.