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

Differently hydrogenated radio frequency-sputtered a-Si layers have been studied by infrared (IR) spectroscopy as a function of the annealing time at 350 Celsius 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

Composition and Thickness of RE Sputtered Amorphous Silicon Alloy Films

Because the composition and the thickness of the thin films are very important forthe fabrication of the devices, in this study we have undertaken the determination of thecomposition and the thickness of the RF sputtered amorphous silicon alloy thin filmsdeposited at room temperature under very different preparation conditions by usingvarious techniques. Incorporation of argon is demonstrated in the room temperaturedeposited films and the thickness of the films measured by different methods such asRutherford backscattering, spectroscopicellipsometry and step-profiler are found to be inreasonable agreement with each other

From nano voids to blisters in hydrogenated amorphous silicon

AFM and FTIR spectroscopy were applied to study thè relationship between surface blisters and nanovoids in annealed hydrogenated a-Si. The influence of thè H bonding configuration on thè way thè nanovoids give rise to thè blisters is discussed. Annealing causes an increase of thè polymers density. As they reside on thè voids walls their density increase causes an increase of thè voids volume. The polymers may release H inside thè voids with creation of H2 gas, whose expansion, upon annealing, further contributes to thè volume increase of thè voids till thè formation of surface blisters

Relationship between structural changes, hydrogen content and annealing in stacks of ultrathin Si/Ge amorphous layers

Hydrogenated multilayers (MLs) of a-Si/a-Ge have been analysed to establish the reasons of H release during annealing that has been seen to bring about structural modifications even up to well-detectable surface degradation. Analyses carried out on single layers of a-Si and a-Ge show that H is released from its bond to the host lattice atom and that it escapes from the layer much more efficiently in a-Ge than in a-Si because of the smaller binding energy of the H-Ge bond and probably of a greater weakness of the Ge lattice. This should support the previous hypothesis that the structural degradation of a-Si/a-Ge MLs primary starts with the formation of H bubbles in the Ge layers