Hydrogen diffusion in a-Si:H stimulated by intense illumination

Hydrogenated amorphous silicon (a-Si:H) films have been thermally annealed at temperatures in the range 220–270 °C for 24–48 h either under intense visible light illumination (4–16 W/${\mathrm{cm}}^2$) or in the dark. After each annealing, the hydrogen-concentration profile was measured with Rutherford-backscattering-spectrometry and elastic-recoil-detection-analysis ion-beam analysis methods. A model is proposed which shows that, in good agreement with our results, the hydrogen-diffusion constant ${\mathit{D}}_{\mathrm{H}}$ is proportional to the power of illumination and also proportional to the loosely bonded hydrogen concentration. Other consequences of the model are discussed.