Temperature dependent line-shape of the silicon dangling bond EPR-resonance in polycrystalline silicon

The temperature dependence of the silicon dangling-bond resonance in polycrystalline (poly-Si) and amorphous silicon (a-Si:H) was measured. At room temperature, electron paramagnetic resonance (EPR) measurements reveal an isotropic g-value of 2.0055 and a line width of 6.5 and 6.1 G for Si dangling-bonds in a-Si:H and poly-Si, respectively. In both materials spin density and g-value are independent of temperature. While in a-Si:H the width of the resonance did not change with temperature, poly-Si exhibits a remarkable T dependence of ΔH_PP. In unpassivated poly-Si a pronounced decrease of ΔH_PP is observed for temperatures above 300 K. At 384 K ΔH_PP reaches a minimum of 5.1 G, then increases to 6.1 G at 460 K, and eventually decreases to 4.6 G at 530 K. In hydrogenated poly-Si ΔH_PP decreases monotonically above 425 K. The decreases of ΔH_PP is attributed to electron hopping causing motional narrowing. An average hopping distance of 15 and 17.5 angstrom was estimated for unhydrogenated and H passivated poly-Si, respectively.