Photoluminescence studies of polycrystalline diamond films

We have used continuous-wave photoluminescence (CWPL) and time-resolved photoluminescence (TRPL) spectroscopies to study the nature of defects in diamond films grown by arc-jet and microwave chemical-vapor deposition (CVD). We observe a series of sharp lines near 1.7 eV in the CWPL spectrum of the arc-jet CVD sample, which we attribute to the presence of interstitial tungsten. In both polycrystalline films we observe broadband luminescence. In the arc-jet CVD material, this consists of two bands, one of which may arise from vibronic coupling of the W levels to the host lattice, and the other from a disordered carbon phase. For the microwave CVD sample, the broadband emission can be divided into two ranges based on the lifetime analysis. Both ranges are primarily vibronic, one being related to the N-V center at 2.155 eV, the other to the N-V center at 1.945 eV. Additionally, a small contribution is attributed to a disordered carbon phase.