Characterization of B-doped polycrystalline diamond films using thermally stimulated luminescence

The effect of different rates of boron incorporation during the growth in diamond on the thermoluminescence (TL) features of this material is investigated. TL studies performed between liquid nitrogen temperature (LNT) and 320 K show some phosphorescence and two other peaks at 226 and 266 K. For the first time, boron level in polycrystalline diamond films was identified by TL by an intense glow peak at 226 K and activation energy of about 0.35 eV. For this main peak, spectral analysis shows a prominent broad band luminescence peaking at 2.56 eV. At 77 K, another emission band was observed at 2.22 eV. This is in agreement with the fact that the recombination mechanisms involve two different recombination centers and, therefore, phosphorescence at 77 K and the main peak at 226 K are of different nature, i.e. the TL peak at 226 K is due to boron while phosphorescence is hence, probably due to a shallow donor level. The behavior of TL intensity relative to the main component at 226 K observed on all the films and linked to boron level decreases with increasing boron concentration.