On the formation of blisters in annealed hydrogenated a-Si layers

Abstract

Differently hydrogenated radio frequency-sputtered a-Si layers have been studied by infrared (IR) spectroscopy as a function of the annealing time at 350°C with the aim to get a deeper understanding of the origin of blisters previously observed by us in a-Si/a-Ge multilayers prepared under the same conditions as the ones applied to the present a-Si layers. The H content varied between 10.8 and 17.6 at.% as measured by elastic recoil detection analysis. IR spectroscopy showed that the concentration of the clustered (Si-H)n groups and of the (Si-H2)n (n ≥ 1) polymers increased at the expense of the Si-H mono-hydrides with increasing annealing time, suggesting that there is a corresponding increase of the volume of micro-voids whose walls are assumed from literature to be decorated by the clustered mono-hydride groups and polymers. At the same time, an increase in the size of surface blisters was observed. Also, with increasing annealing time, the total concentration of bonded H of any type decreases, indicating that H is partially released from its bonds to Si. It is argued that the H released from the (Si-H)n complexes and polymers at the microvoid surfaces form molecular H2 inside the voids, whose size increases upon annealing because of the thermal expansion of the H2 gas, eventually producing plastic surface deformation in the shape of blisters.

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

“…In previous studies of our group on a-Si:H layers submitted to annealing it was found that the cause of the structural degradation of the layers in the shape of blisters and craters was the change of the hydrogen bonding configuration [17][18][19][20]. In this paper we investigate whether this also occurs in a-Ge:H by submitting as-deposited films with different H content to annealing.…”

Investigation of Thermal Stability Effects of Thick Hydrogenated Amorphous Silicon Precursor Layers for Liquid‐Phase Crystallized Silicon

“…We note that pinhole formation in a-Si:H films as visible in Figure 7, has been reported quite often in literature [29,[48][49][50][51] since first described by Shanks et al [46,47] It has been attributed to a poor a-Si:H-substrate interface and the build-up of H 2 pressure in cavities at this interface upon H out-diffusion into these cavities from a-Si:H during film deposition and/or upon annealing. According to Figure 6a, such pinholes and bubbles are present in our unstable material already in the as-deposited state.…”

Temperature-induced nanostructural evolution of hydrogen-rich voids in amorphous silicon: a first-principles study

“…10 For amorphous materials, annealing also increases the degree of local ordering in the amorphous environment. Earlier studies by small-angle X-ray scattering (SAXS) reported the presence of columnar-like geometric structure 11 and blister formation in annealed samples of a-Si:H. 12 Likewise, experiments on a-Si/a-Si:H, using positron-annihilation lifetime spectroscopy, have indicated that annealing above 673 K can lead to the formation of voids via vacancy clustering, which affects the nanostructural properties of the network. 13,14 It has been suggested that at higher temperature, near 800 K, a considerable restructuring can take place in the vicinity of the void boundary that can modify the shape and size of the voids.…”