The dark ESR measurements on a-Si : H were carried out at room temperature. The spin density decreases with increasing substrate temperature.
Some structures are identified for the first time in the dark ESR spectra of undoped samples with lower spin densities. Besides the usual line with g=2.0055, two more resonances are found with g=1.998 and g=2.013.
In a phosphorus doped(0.05 vol %) sample, a signal with g=2.017 is seen while the line with g=2.0055 is obscured.
The g-factors found in this work are very similar to those in the optically detected magnetic resonance experiments reported by other authors.
Annealing removes the signal with g=1.998 for undoped samples and that with g=2.017 for doped sample. The line with g=2.0055 increases with annealing at higher than deposition temperature, irrespective of doping.
Possible origins of the ESR lines are discussed. Especially, a hydrogen-involved defect is suggested to be the ESR center of the line with g=1.998.