Eventually, the voids will reach such a big size to cause a lift-off of the layers with the formation of surface blisters, as observed by AFM. The blisters correspond therefore to bubbles containing selleck molecular H2. They have developed from microscopic cavities, decorated by clustered mono-hydrides and (Si-H2) n , n ≥ 1, complexes, which have increased their volume because of the increase of the inside pressure due to the thermal expansion of the H2 gas upon annealing. It was seen in previous works on a-Si, a-Ge layers and a-Si/a-Ge multilayers that

for annealing time and/or temperature higher than those considered here, further degradation of the layer surface occurs by explosion of the blisters [19, 20]. Table 2 Total integrated intensity (cm −1 ) of the IR stretching mode Annealing time (h) I SM(cm−1)   H = 0.4 ml/min H = 0.8 ml/min H = 1.5 ml/min    0 12.8 30.8 72.1    1 11.4 26.8 52.5    4 10.5 24.2 45.1 Total integrated intensity (cm−1) of the IR stretching mode, I SM, as a function of annealing time for the different hydrogenation rates. Selleck AZD6244 Conclusions The origin of surface blisters that form in hydrogenated

RF-sputtered a-Si layers submitted to annealing has been investigated by studying the evolution of the Si-hydrogen bonds by means of IR spectroscopy. By increasing the annealing time and/or H content, the blister size increased. Correspondingly, IR spectroscopy showed that the density of the isolated Si-H mono-hydrides decreased, while JNJ-64619178 nmr the concentration of the clustered (Si-H) n groups and (Si-H2) n , n ≥ 1, polymers increased. As both these complexes

reside on the inner surfaces of voids, it is concluded that their accumulation at such surfaces favours the void size increase. It was also seen that the total amount of bonded H decreased upon annealing, suggesting that some H is released from its bonds to Si. The H liberated from the (Si-H) n groups and (Si-H2) n polymers decorating Bumetanide the void surfaces is expected to form molecular H2 within the voids. The expansion of the H2 gas would cause further growth of the voids up to a size able to produce surface blistering. Authors’ information MS is a scientific adviser at the Institute of Technical Physics and Materials Science, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, Hungary. CF is a senior scientist at the IMEM Institute of the Consiglio Nazionale delle Ricerche, Parma, Italy. ZS is a PhD student and young researcher at the Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Budapest, Hungary. KK is a research professor at the Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Budapest, Hungary. LN is a researcher at the IMEM Institute of the Consiglio Nazionale delle Ricerche, Parma, Italy.