Phosphorous–oxygen hole centers in phosphosilicate glass films

Abstract

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 $1326(2)\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ and the broad feature at about $1150\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ 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 (${\mathrm{POHC}}^{\mathrm{s}}$ and ${\mathrm{POHC}}^{\mathrm{m}}$ respectively). Density functional theory calculations have been performed to determine the structure, charge and spin distribution, hyperfine coupling constants, and $g$ values of ${\mathrm{POHC}}^{\mathrm{s}}$ and ${\mathrm{POHC}}^{\mathrm{m}}$ 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 et al. regarding the structure of the paramagnetic centers and of their diamagnetic precursors. ${\mathrm{POHC}}^{\mathrm{s}}$ is a phosphorous\char21{}oxygen hole center characterized by the presence of two $\mathrm{P}\mathrm{O}$ terminal bonds, ${[{(\mathrm{O})}_{2}\mathrm{P}(\mathrm{O})_{2}{}^{\mathbf{∙}}]}^{0}$; ${\mathrm{POHC}}^{\mathrm{m}}$ contains only one $\mathrm{P}\mathrm{O}$ terminal bond, ${[{(\mathrm{O})}_{3}\mathrm{P}{\mathrm{O}}^{\mathbf{∙}}]}^{+}$. These centers result from the trapping of a hole by ${[{(\mathrm{O})}_{2}\mathrm{P}{(\mathrm{O})}_{2}]}^{\ensuremath{-}}$ and ${[{(\mathrm{O})}_{3}\mathrm{P}\mathrm{O}]}^{0}$, respectively. While the EPR signal of ${\mathrm{POHC}}^{\mathrm{m}}$ overwhelms the one of ${\mathrm{POHC}}^{\mathrm{m}}$, the Raman main band is related to the precursor of ${\mathrm{POHC}}^{\mathrm{m}}$.