Intermixing time ti and interdiffusion coefficients D of nanometer periods Si/Ge strained layer superlattices (SLSs) were measured by Raman scattering technique. Si12Ge12 and Si19Ge9 SLSs have been annealed in the temperature range 760–900 °C during various time intervals. The observed D and ti follow the Arrhenius-like behavior with different activation energies ΔE=1.78±0.15 eV and 3.94±0.15 eV and pre-exponential factors D=2×10−10 cm2 s−1 and 0.7 cm2 s−1, respectively, for the Si12Ge12 and Si19Ge9 SLSs. D, ti, ΔE, and D0 are strongly affected by the changes of the SLS layer thickness, and strain. An explanation of the experimental observations is proposed in terms of the kinetic electron-related theory of atomic diffusion in solids. The observed variations of ΔE and D0 are related to the material parameters, which are characterized by picosecond atomic and electronic phenomena in nanometer regions, in good agreement with the observations.

The kinetics of processes related to the formation of C49 and C54 Ti(Si1−yGey)2 germanosilicide phases in the two relaxed and strained Ti/Si1−xGex systems (x1=0.35 and x2=0.20) in the temperature range 600–800 °C are considered. These processes have been studied through Auger electron spectroscopy, secondary ion mass spectroscopy, x-ray diffraction, and Raman scattering spectroscopy supported by ion beam etching techniques. Si/Ge ‘‘intergrain’’ alloy has been found between the grains of the C49 or/and C54 phases, with a Ge-rich part Si1−zGez of z=2x–3x in the upper region. At higher temperatures, the Ge concentration in the Ge-rich alloy decreases and its volume increases. The temperature required for obtaining similar changes are higher when x2<x1. A kinetic electron-related model is proposed to explain the observed phenomena.

Superlattices (SL s) composed of thin Si and Ge layers (Si»Ge», Si»Ge9) have been implanted with As, Ge, and Ga ions with doses ranging from 1 X 10" to 1 X 10' ions cm, and thermally annealed at 600 C for 30 min. The disordering and the intermixing of these SL s have been studied by the Ramanscattering technique and model calculations. The damage created by ion implantation has been estimated using TRIM simulations and a model. We found that when a thin symmetric Si»Ge» SL was rendered amorphous by ion implantation at high doses 5 X 10' ions cm, a mixed Sio &Geo 5 material was produced by thermal annealing, but the crystalline structure of the asymmetric Si»Ge9 SL equally disordered and annealed returns to a different SL structure with very little intermixing between the layers. Using a kinetic model, we calculated the interdiffusion coefficients and it was found that the recrystallization of the Ge layer is a fast process but that of the Si one is slow with respect to the time needed for intermixing. As a result, Ge diffuses mainly in disordered Si layers and Si in ordered Ge layers. In order to explain our experimental results, we equate the diffusion of Si into crystalline Ge to that of Ge into amorphous Si to minimize the effect of interlayer stress. Model calculations explain the difference in behavior between the two types of SL's, and are in good agreement with the Raman data.

Thin SimGen superlattices (SLs) have been implanted with dopant and neutral ions and annealed at low temperature (600 °C) during a short time (30 min). Intermixing between the two species takes place when the SL has been rendered amorphous. This effect is due to disorder only and no dopant impurity influence could be seen in contrast to the case of III–V SLs.

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