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In this work a strict comparison of the results obtained on InGaAs/GaAs heterostructures by HRXRD and RBS-channeling analysis shows a discrepancy in the In atomic fraction determined by the two techniques. The discrepancy leads to a difference in the reference lattice parameter of the relaxed film and, therefore, changes the description of the strain relaxation rate. After a discussion on the possible reasons for this discrepancy, the results have been interpreted as the influence of the atomic degrees of freedom internal to the lattice unit cell which could determinate the equilibrium

The structural characterization of ZnS epilayers grown on (100) GaAs by H 2 transport vapour-phase epitaxy is reported. High-resolution X-ray diffraction and ion channelling Rutherford backscattering spectrometric measurements were used to evaluate the overall crystalline perfection of the epilayers and the distortion and reciprocal orientation of the ZnS and GaAs lattices and to measure the epilayer built-in lattice strain. High crystalline quality can be achieved at the surface of relatively thick (above ca. 1 μm) ZnS layers, although a dense distribution of extended defects was observed close to the ZnS/GaAs interface. It turns out that the ZnS unit cell is orthorombically distorted, although its deviation from a purely tetragonal distortion is very small. Systematic measurements of the ZnS lattice strain were performed on the epilayers and the results were compared with the thermal strain value obtained by temperature-dependent X-ray diffraction measurements. The data indicate that the ZnS built-in lattice strain can be entirely ascribed to a thickness-dependent thermal strain contribution, the initial lattice misfit at the growth temperature being almost totally relaxed even for relatively thin epilayers. Finally, no appreciable strain was found for epilayer thicknesses above about 3 μm.

We report on the structural characterization by ion channelling Rutherford backscattering spectrometry (RBS) of thin (less than 3 μm) CdS epitaxial layers grown on {111}A-oriented CdTe substrates by chemical vapour deposition. The overall crystalline quality of the present epilayers has been studied as a function of their thickness. Also, the occurrence of single crystal growth vs. highly textured polycrystalline growth has been checked by studying channelling angular dips at different 4 He + beam energies. The CdS epilayers turned out to be essentially single crystalline, although the present RBS measurements show that extended defects are contained in the layers and at the CdS/CdTe interfaces. The dechannelling beam energy dependence allows us to identify these defects as stacking faults, whose concentration profile in the epilayers is reported.

The elemental composition and the optical properties of hydrogenated amorphous GaAs prepared by r.f. reactive sputtering at different hydrogen and argon pressure and substrate temperature have been determined. From the dependence of the absorption coefficient on photon energy the optical gap has been deduced according to the Tauc law. The data obtained for stoichiometric samples are compared with similar data obtained by different authors. The influence of various deposition parameters on stoichiometry and on the optical properties is briefly discussed.

In this work the silicon self-interstitial (I) diffusion in trap-containing molecular beam epitaxy Si layers is investigated. The I’s are produced by Si ion implantation, and the I supersaturation is reported as a function of the depth and the annealing time. These data are discussed on the basis of two alternative models proposed in literature (“effective diffusivity” model and “filling trap” model). This analysis demonstrates that the second model is more appropriate to describe the proposed phenomenology, since it explains both the increase of the I penetration depth as a function of the implant dose and the very rapid change of the supersaturation versus time. Moreover, the proposed model takes account for the I recombination at the surface.

We report on the direct measurements of surface lattice strain in ZnTe epitaxial layers on {100}GaAs substrates by ion channeling Rutherford backscattering spectrometry and low-temperature (10 K) reflectance spectroscopy measurements. The measured ZnTe strain is the superposition of the expected thermal (tensile) strain and a thickness-dependent residual compressive strain. Our data indicate that the removal of this residual strain is slower than the rate predicted by the equilibrium theory, following an apparent h^(-1/2) power-law dependence on the epilayer thickness h, above approximately 100 nm.

It is well-known that in the case of high lattice mismatch the growth of semiconductor structures proceeds via island formation. The growth and characterization of the so obtained nanostructures has attracted increasing interest in the last few years due to their fascinating potential applications in integrated microelectronics. Apart from optical and electrical characterization, the structural analysis of these structures is usually performed by Scanning Electron Microscopy, Transmission Electron Microscopy or Atomic Force Microscopy. However, none of these techniques is suitable to exactly measure the total amount of deposited materials which is, together with the statistical distribution of the dimensions of the nanostructures, the most important information to be obtained. We have developed a new experimental set up for RBS analysis which, in connection with a computer simulation code, improves the thickness resolution of the technique of nearly one order of magnitude. With this experimental arrangement InAs/GaAs, InP/GaAs and InGaAs/GaAs nanostructures, nominally few monolayers (ML) thick can be analyzed by obtaining the total amount of deposited material, the fraction of the surface covered by the nanostructures and their maximum thickness.

The thermal oxidation of polycrystalline zirconium implanted with 21 different ion species has been studied by using the nuclear reaction 16 O( d , p 1 ) 17 O. A very good agreement has been found between the oxidation kinetics of unimplanted zirconium as determined by the nuclear reaction and those previously measured gravimetrically. Oxidation kinetics show a time dependence which is cubic or parabolic depending upon the surface treatment before oxidation. Ion implantation produces significant changes in oxidation rate but the time dependence remains the same. A strong correlation has been found between the behaviour of ion implanted systems and that reported for binary alloys, confirming the hypothesis that the ionic size of the additive is the major parameter governing the influence upon the oxidation of zirconium. The implanted species which inhibit oxidation possess ionic radii lying between 80% and 100% of that of Zr 4+ . An explanation of their beneficial effect based on an increase of the plasticity of the growing oxide is presented.

The crystalline and optical quality of ZnS epilayers grown on (100)GaAs by MOVPE was investigated by channeling-RBS, 10 K photoluminescence and absorption spectroscopy for different growth conditions. The measurements point out that the crystalline and optical quality of the epilayers strongly depends on the VI II precursor vapor phase stoichiometry as well as on GaAs surface treatments before the growth. Optimized MOVPE growth conditions have been determined.