On the mechanisms of hydrogen-induced blistering in RF-sputtered amorphous Ge

Diffusion and reaction kinetics governing surface blistering in radio frequency sputtered hydrogenated a-SixGe1-x (0 ≤ x ≤ 1) thin films

“…Let choose these layers with thickness =40nm to be located at the Hence r Si =0.11 for Si and r Ge =0.04 for Ge. The H would leave the layer with thickness =40nm located at the interface to the substrate in H 2 molecular form because blistering would be followed by crater formation [7]. However, since in our case the critical temperature T* we are looking for is by definition lower than the temperature θ there is no interface at the x=δ line in our model; no bubble is formed and thus no H 2 is produced.…”

“…SEM images of blisters and craters on annealed samples. An a-Ge:H sample has been annealed at 180 O C for 10 (a) and 40 (b) minutes.For the a-Ge:H layers it was shown earlier by ERDA and SNMS[7] that the total H content is lower in the annealed samples with respect to the not-annealed ones. In the latter ones the amount of hydrogen decreases on going from the layer bottom, i.e.…”

“…2a), which correspond to bubbles containing molecular H 2 [7,13,14]. These bubbles have developed from nano-and micron-sized cavities that have increased their volume because of the increase of the inside pressure due to the thermal expansion of the H 2 gas upon annealing [7,13,14]. Finally the cavities filled with H 2 pop-up and create observable blisters that transform into craters for too long annealing times or too high temperatures ( Fig.…”

“…It has been widely demonstrated that in amorphous Ge, Si and SiGe [7,8,15,18], as well as in other materials [19], the reason for the formation of blisters is the increase of the volume of voids containing molecular H 2 until they pop up and deform the surface. In as-grown hydrogenated a-Si x Ge 1-x , 0 ≤ x ≤1, H is mostly bound to the host atoms Si and Ge.…”

“…The accumulation on the wall of voids causes the evolution of hydrogen bubbles and then the formation of blisters. Some efforts have been made to understand the microscopic mechanisms determining the rupture of the MeH bonds and formation of H 2 rich voids at the origin of the blisters [6][7][8] in order to get rid of them. For this purpose a method was recently proposed for a-Si:H which is based on the optimization of the shape, size and thickness of the layer [9] .…”