Evidence for Exchange Between Free and Deep Hydrogen (Deuterium) During Diffusion
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EVIDENCE FOR EXCHANGE BETWEEN FREE AND DEEP HYDROGEN (DEUTERIUM) DURING DIFFUSION HOWARD M. BRANZ*, SALLY ASHER*, YUEQIN XU* AND MATHIEU KEMP** *National Renewable Energy Laboratory, Golden, CO 80401 USA "**Dept.of Engineering Physics, Ecole Polytechnique, Montreal, Quebec, Canada ABSTRACT We do not observe any immobile deuterium in secondary ion mass spectrometry D profiles taken after long anneals of hydrogenated amorphous silicon sandwich structures with a thin deuterated interior layer. This suggests that a single deep H level (-1.4 eV deep) controls H diffusion. On its face, our result contradicts nuclear magnetic resonance and H effusion measurements that show about 30% of H in a-Si:H is "isolated" and deeply bound (- 2.1 eV deep). We reconcile our experimental results with the existence of isolated deep H by assuming there is a low-barrier (
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