Aa. Onischuk et al., Pulsed EPR hole-burning experiment on dangling bond centers in a-Si : H aerosol particles formed by thermal decomposition of silane, APPL MAGN R, 17(1), 1999, pp. 65-75
Si dangling bond centers in aerosol particles of amorphous hydrogenated sil
icon formed by thermal decomposition of SiH4 in Ar were studied by pulsed e
lectron paramagnetic resonance. The hole-burning and inversion-recovery exp
eriments demonstrate that large-scale rapid spectral diffusion takes place
in the samples with high spin concentration. Correlation times tau(c) of th
e spectral diffusion and spin-lattice relaxation times T-1 were obtained in
the temperature range between 77 and 290 K. Above 130 K, tau(c), and T-1 a
re proportional one to the other. The unusual feature of this spectral diff
usion is that the shape of the central part of the spectral hole does not c
hange when the delay time increases. The other paramagnetic centers previou
sly investigated showed a remarkable change of the hole shape which was ind
uced by modulation of dipolar interaction due to spin flips. It is suggeste
d that the observed anomaly in the Si dangling bond centers arises due to c
ooperative spin flips.