Multilayers of hydrogenated ultrathin (3 nm) amorphous a-Si and a-Ge layers prepared by sputtering have been studied by atomic force microscopy (AFM) and transmission electron microscopy (TEM) to check the influence of annealing on their structural stability. The annealed multilayers exhibit surface and bulk degradation with formation of bumps and craters whose density and size increase with increasing hydrogen content and/or annealing temperature and time. Bumps are due to the formation of H2 bubbles in the multilayer. The craters are bumps blown up very likely because of too high a gas pressure inside. The release of H from its bonds to Si and Ge occurs within cavities very likely present in the samples. The necessary energy is supplied by the heat treatment and by the recombination of thermally generated carriers. Results by energy filtered TEM on the interdiffusion of Si and Ge upon annealing are also presented

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Al2O3 (5 nm)/Si (bulk) sample was subjected to irradiation of 5 keV electrons at room temperature, in a vacuum chamber (pressure 1 × 10−9 mbar) and formation of amorphous SiO2 around the interface was observed. The oxygen for the silicon dioxide growth was provided by the electron bombardment induced bond breaking in Al2O3 and the subsequent production of neutral and/or charged oxygen. The amorphous SiO2 rich layer has grown into the Al2O3 layer showing that oxygen as well as silicon transport occurred during irradiation at room temperature. We propose that both transports are mediated by local electric field and charged and/or uncharged defects created by the electron irradiation. The direct modification of metal oxide/silicon interface by electron-beam irradiation is a promising method of accomplishing direct write electron-beam lithography at buried interfaces.

The optical parameters of hydrogenated amorphous a-$$\hbox {Si}_{1-x}\,\hbox {Ge}_{{x}}$$ Si 1 - x Ge x :H layers were measured with focused beam mapping ellipsometry for photon energies from 0.7 to 6.5 eV. The applied single-sample micro-combinatorial technique enables the preparation of a-$$\hbox {Si}_{1-x}\,\hbox {Ge}_{{x}}$$ Si 1 - x Ge x :H with full range composition spread. Linearly variable composition profile was revealed along the 20 mm long gradient part of the sample by Rutherford backscattering spectrometry and elastic recoil detection analysis. The Cody-Lorentz approach was identified as the best method to describe the optical dispersion of the alloy. The effect of incorporated H on the optical absorption is explained by the lowering of the density of localized states in the mobility gap. It is shown that in the low-dispersion near infrared range the refractive index of the a-$$\hbox {Si}_{1-x}\,\hbox {Ge}_x$$ Si 1 - x Ge x alloy can be comprehended as a linear combination of the optical parameters of the components. The micro-combinatorial sample preparation with mapping ellipsometry is not only suitable for the fabrication of samples with controlled lateral distribution of the concentrations, but also opens new prospects in creating databases of compounds for optical and optoelectonic applications.

A study is presented of the structural changes occurring as a function of the annealing conditions in hydrogenated amorphous Si/Ge multilayers prepared by sputtering.Annealing changes the structure of the as-deposited multilayer except for the less severe conditions here applied (150 °C, time < 22 h). For higher temperatures and/or times, the modifications consist of layer intermixing and surface degradation in the shape of bumps and craters. They are argued to be due to the formation of H bubbles upon heating.Hydrogen should be mostly released from the amorphous Ge layers.

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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.

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