Phosphorous-oxygen hole centers in phosphosilicate glass films

Phosphosilicate glass films produced by subatmospheric pressure chemical vapor deposition with different phosphorus concentrations have been investigated by ultraviolet Raman spectroscopy and electron paramagnetic resonance (EPR) spectroscopy. The behavior and the attribution of the main Raman band at 1326(2) cm(-1) and the broad feature at about 1150 cm(-1) are discussed in detail. After room temperature x-ray irradiation, EPR spectra reveal resonance signals attributed to a stable and metastable variant of the phosphorous oxygen hole centers (POHCs and POHCm respectively). Density functional theory calculations have been performed to determine the structure, charge and spin distribution, hyperfine coupling constants, and g values of POHCs and POHCm and the structural and vibrational properties of their diamagnetic precursors. The comparison between the experimental data and the theoretical predictions supports the original tentative assignment proposed by Griscom regarding the structure of the paramagnetic centers and of their diamagnetic precursors. POHCs is a phosphorous-oxygen hole center characterized by the presence of two P - O terminal bonds, [(O -)(2)P(= O)(2)(center dot)](0); POHCm contains only one P - O terminal bond, [(O -)(3)P - O-center dot](+). These centers result from the trapping of a hole by [(O -)(2)P(= O)(2)](-) and [(O -)(3)P = O](0), respectively. While the EPR signal of POHCm overwhelms the one of POHCm, the Raman main band is related to the precursor of POHCm.