Dielectric properties of conducting boron-doped diamond

We extract the infrared dielectric function from Fourier transform infrared reflectance spectra 650−4000cm −1 for conducting single crystal and polycrystalline boron-doped (3−6×10 20 cm −3 ) diamond (BDD) by Kramers–Kronig (K–K) analysis, validating our method on commercial SiC substrates. This method highlights the importance of using integrable functions in K–K, solving issues with convergence near the end-points of the measurement spectral range. Polycrystalline BDD shows an elevated optical index ∼3−3.5 below 2000cm −1 compared to the ∼2.5−2.7 in single-crystal BDD, and the ∼2.4 for ideal diamond, accompanied by increased dielectric loss at ∼1250cm −1 , termed the L2-mode. Raman mapping of this IR-active ω L2 revealed elevated levels of graphitic sp 2 inclusions, particularly at grain boundaries. These optical measurements are consistent with polycrystalline BDD showing lower electrical resistivity 0.05Ω-cm, one order lower than that of the single crystal 0.6Ω-cm, highlighting the strong role of sp 2 inclusions in grain boundary conductivity as a source of dielectric loss. These results show that extrinsic factors beyond B-doping alone should be considered in the interpretation of the optoelectronic properties of BDD and inform its use for thermal management in codesigned microelectronics for power and RF systems, plasma-assisted epitaxy of cubic boron nitride and electrochemistry.