Modulation and thermal stability of hydrogen in amorphous silicon

Hydrogenated amorphous silicon can be obtained by reactive evaporation of silicon under a flow of hydrogen atoms. By modulating the pressure of hydrogen, it is possible to prepare multilayers of type Si/Si:H/Si/Si:H/ … with thicknesses of bilayers less than 90 Å. Low-angle X-ray scattering shows diffraction peaks corresponding only to the modulation of atomic density, but low-angle neutron scattering permits to see the modulation of the isotopes hydrogen and deuterium. The thermal stability of the silicon atomic density modulation and of the hydrogen modulation is discussed.