Proton NMR Hole-Burning in Hot Wire a-Si:H

Proton NMR near 200 MHz has been used to examine the dynamics of hole-burning in HWCVD a-Si:H films deposited from SiH4. Radiofrequency hole-burning is a tool to distinguish inhomogeneous broadening from homogeneous broadening. The 3 kHz FWHM resonance line from T-site-trapped H2 molecules shows a hole-burn behavior similar to that found for PECVD a-Si:H films, as does the 24 kHz FWHM line from clustered silicon-bonded hydrogens. However the ∼80 kHz FWHM superbroad line varies with tip angle uniformly across the line for hole-burns applied at any location within ∼50 kHz from the resonance center. The superbroad line is homogeneously broadened and apparently arises from superclose SiH clusters with inter-proton distances considerably less than 2 A.