BCl₃ mediated homoepitaxial CVD growth of p-type diamond for NV^- center charge stability

The nitrogen vacancy (NV^-) center in diamond is a potent room temperature quantum sensor but its spontaneous switching to NV⁰/NV⁺ charge states is detrimental to its performance. NV^- charge stability can be controlled by electrical manipulation in p-i-n diode structures [PRX 4.1, 011057 (2014)]. This motivates us to explore the growth of p-type B-doped diamond (BDD) films using chemical vapor deposition (CVD). We describe the homoepitaxial CVD growth of p and p⁺ type BDD films using less toxic halide precursor - BCl₃, followed by characterization using atomic force microscopy (AFM), Raman spectroscopy, and low temperature electrical transport. AFM reveals atomically flat terraces/islands (R_q < 1 nm) interspersed with pyramidal pits. Raman spectroscopy shows B-C/ B-B vibrational modes and a redshifted diamond zone-center phonon line. We also discuss the superconducting behavior of these BDD films. In context of earlier studies [Phys. Stat. Sol.(a)154, 385 (1996)], we explore the effect of halide dopant gas on surface morphology, opening a safer, more efficient alternative for fast CVD growth of smooth p/p⁺ type BDD films.