The phenomenon of radiation-induced hydrogen migration was studied in

hydrogenated amorphous silicon (a-Si:H) using layer stacks of SiO2/a-Si:H/SiO2.

The top and bottom SiO2 layers were deposited by magnetron sputtering at room

temperature. The intermediate a-Si:H layers were deposited using plasma-enhanced

chemical vapour deposition at three temperatures—room temperature, 150 and

270C. The samples were irradiated with MeV 15N ions during nuclear reaction

analysis of hydrogen concentration. It was established that the irradiation leads to

hydrogen migration and redistribution, which depend on the a-Si:H deposition

temperature. The symmetric hydrogen concentration profile in the as-prepared

layer stack becomes asymmetric after the irradiation due to increase in the hydrogen concentration in the bottom SiO2 layer. Hydrogen concentration in the

layer stacks decreased during the initial irradiation stage and then remains constant.

In contrast, hydrogen loss from the a-Si:H layer proceeds gradually and

continuously with increasing radiation fluence. It was suggested that the hydrogen

atoms liberated by the MeV ion irradiation do not recombine in molecules and that

the hydrogen migration in a-Si:H was related to the diffusion of the hydrogen

atoms. The radiation-induced asymmetry of the hydrogen profiles in the layer stack

implied that there was a difference in the diffusion parameters at the inner and

outer interface.

Ion Beam-Induced Hydrogen Migration in a SiO2/a-Si:H/SiO2 Layer Stack.

B.Pantchev, P.Danesh, B.Schmidt, D.Grambole, W.Möller: Semiconductor Science

and Technology, 2009, 24[3], 035012