This paper deals with the growth by molecular beam epitaxy of semimetallic (rare-earth group V element) compounds on III-V semiconductors. Results are presented, first on the Er-Ga-As and Er-Ga-Sb ternary phase diagrams, second on the lattice-mismatched ErAs/GaAs (δa ≈ +1.6%), YbAs/GaAs (δa/a = +0.8%), and ErSb/GaSb (δa/a ≈ +0.2%) heterostructures, and third on the lattice-matched Sc0.3Er0.7As/GaAs and Sc0.2Yb0.8As/GaAs systems (δa/a < 0.05%). Finally the growth of YbSb2 on GaSb(001) is reported. The studies made in situ by reflection high-energy electron diffraction (RHEED) and x-ray photoelectron diffraction and ex situ by x-ray diffraction, transmission electron microscopy, He+ Rutherford backscattering, and photoelectron spectroscopy are presented. We discuss the atomic registry of the epitaxial layers with respect to the substrates, the appearance of a mosaic effect in lattice-mismatched structures, and the optical and electrical properties of the semimetallic films. The problems encountered for III-V overgrowth on these compounds (lack of wetting and symmetry-related defects) are commented on, and we underline the interest of compounds as YbSb2 which avoid the appearance of inversion defects in the GaSb overlayers.

Magnetization, magneto-optical Kerr effect and Hall effect have been measured on sputtered Pt/Au/Co/Pt/SiO2/Si samples with Co thickness tCo=0.7nm and Au thickness tAu up to 1nm. In the temperature range 50–300K the extraordinary Hall effect displays a standard (aρ+bρ2) behavior versus the resistivity ρ, with a dominant contribution of the first “skew scattering-like” term. The second “side jump-like” term changes sign with increasing tAu, which could be related to the progressive change of the upper interface, from a complex interdiffused Pt/Co interface to an Au/Co one.

Dynamic optical coupling is performed to caracterize a 4 single-mode fibres ribbon inserted and bonded into dry etched U-grooves. A comparison is made with mechanical and chemical V-grooves.

A new concept is proposed for lensed fibres fabricated according to a collective and low cost process. This process is based on the cleaving and splicing of optical fibre ribbons and is suitable for the coupling of laser diode arrays and fibre ribbons.

The magnetotransport properties are an attractive alternative to standard observation techniques for the characterization of the magnetization reversal in structures with reduced lateral dimensions (stripes). In particular, magnetic films exhibit the so-called anomalous Hall effect which is very sensitive to the local magnetic domain structures. We began to work with the model system Co/Au(111) grown on silicon dioxide. We present here a new method for microstructuring magnetic multilayers, that avoid the use of technological processes on the multilayers. Preliminary magnetotransport results in 50 μm wide stripes are presented and discussed.

Successful growth of ErSb(001) single crystal layers on GaSb(001) substrates has been demonstrated. The reflection high-energy electron diffraction patterns show a (4×4) surface reconstruction. Reflection high-energy electron diffraction oscillations, x-ray diffraction, and Rutherford backscattering with channeling indicate single crystal monolayer-by-monolayer growth and continuity of the Sb sublattice at the ErSb/GaSb interface. The ErSb has a low room temperature resistivity equal to 30 μΩ cm but may be used as a metallic reflector only for wavelengths greater than 2.4 μm. The overgrowth of GaSb on ErSb leads to mirrorlike surfaces but the overlayers contain symmetry-related defects. On the contrary, nearly perfect GaSb overlayers were grown on [ErSb,GaSb] superlattices which exhibit metallic behavior.

YBa2Cu3O7 thin films and YBa2Cu3O7-based insulator/superconductor superlattices have been grown by pulsed laser deposition on homoepitaxial SrTiO3 buffer layer. The SrTiO3 buffer layer decreases the substrate roughness, improving the epitaxial relation of the YBa2Cu3O7 layer or YBa2Cu3O7/PrBa2Cu3-xGaxO7 superlattices with the substrare, as shown by Rutherford backscattering spectrometry in channelled geometry and RHEED analyses performed at the end of the growth. However, this does not result in a significant smoothness improvement of the YBa2Cu3O7 film measured by atomic force microscopy. The X-ray diffraction patterns recorded from YBa2Cu3O7/SrTiO3 superlattice structures show only ±1 satelite around the (100) reflection line. The poor quality of the superlattice is attributed to the SrTiO3 regrowth mechanisms over YBa2Cu3O7 which develop a high roughness into the YBa2Cu3O7/SrTiO3 inverse interface, although the SIMS in-depth profiles show a perfect chemical periodicity while the growth temperature is lower than 710°C.

Solid state interdiffusions between a thin film of erbium deposited under vacuum conditions and (001) and (111) GaAs substrates were investigated in the temperature range 350-800-degrees-C. Complementary analysis methods (RBS, X-ray diffraction) allow us to point out, according to annealing temperatures, successives steps of the interaction corresponding to different mixtures of phases, essentially binaries. These steps are strongly depending on the GaAs substrate orientation, especially the final step of the interdiffusions. On (001) GaAs, only two steps have been observed : no visible interaction is noticed between erbium and GaAs before 600-degrees-C; the interaction begins at 600-degrees-C. evolves slightly and leads at 800-degrees-C to the nominal composition << Er10GaAs >> which corresponds to a mixture of several phases Er5Ga3, Er and ErAs. On (111) GaAs. several steps of interaction have been found ; first of all, erbium reacts with the substrate at 400-degrees-C (Er5Ga, + Er mixture). then the reaction is continuing at 600-degrees-C (Er5Ga3 + Er + ErAs mixture) before reaching at 800-degrees-C the nominal composition << Er1.5GaAs >>, which is in fact a mixture of the three binaries ErAs + ErGa2 + Er3Ga5. It can be noticed that the 800-degrees-C annealing is not sufficient to reach the mixture of the phases ErAs + Ga which, according to the ternary phase diagram, should be the final stage of the interaction Er/GaAs. The analysis of the Er/GaAs interdiffusions shows that ErAs is the << key >> compound around which the interaction progresses. This compound appears as an ideal candidate to realize epitaxial ErAs/GaAs heterostructures.

Superlattices of YBA2Cu3O7−δ/PrBa2Cu3−xGaxO7−δ (x = 0.2) have been grown by multitarget pulsed-laser deposition on SrTiO3{100} and MgO{100} substrates with their c-axis either normal or parallel to the substrate surface, depending on the growth temperature. At a temperature of 785°C the multilayers are deposited with the c-axis normal to the substrate surface, but with a buffer layer of PrBa2Cu3−xGaxO7, grown at a lower temperature (650°C), the superstructure becomes c-parallel. Secondary-ion mass spectrometry reveals no interdiffusion between Y and Pr, and no diffusion of Ga into the YBa2Cu3O7−δ layer. Nevertheess, the profiles of the c-normal-oriented superlattice are sharper than the c-parallel ones. The 15% minimum yield (χmin) measured from RBS in channeling geometry for the c-normal superlattices indicates highly textured growth on SrTio3, contrary to that which is observed for c-parallel superlattices (χmin = 28%) and for c-normal structures grown over an MgO substrate (χmin = 50%). The low interface roughness of the c-normal multilayers grown on SrTiO3 is demonstrated by AFM measurements, which give a standard deviation lower than 1.6 nm over 6.25 βm2, and also by the streaky RHEED patterns observed at the end of the growth.

Solid-state interdiffusions at the Ni/GaSb(111) and (001) interfaces were investigated in the temperature range 200–600 °C using 1.8 MeV He+ ion backscattering and channeling and also using x-ray diffraction. The starting point was the experimental determination of the Ni-Ga-Sb phase diagram. The steps of the interaction were the same for GaSb(111) and GaSb(001). Three various phases were observed: the ternary A phase with the Ni2.5GaSb atomic composition, Ni2Ga3, and Ni2Ga0.25Sb1.75, the Ga-rich limit of the substituted NiSb binary compound. All these phases had a hexagonal pseudocubic structure. First, an epitaxial Ni2.5GaSb A phase reacted layer was obtained. This phase was not in thermodynamical equilibrium with GaSb and the final product was a mixture of Ni2Ga3 and Ni2Ga0.25Sb1.75 grains with an average atomic composition equal to Ni1.6GaSb. The metallurgical behavior of the Ni/GaSb contacts was compared to that of the Ni/GaAs and Ni/AlAs contacts. It was concluded that the experimental ternary diagram allowed a correct estimation of the sequence of phase formation in metal/compound semiconductor contact. In contrast, due to major differences in the ternary phase diagrams, the steps of the solid phase interdiffusion cannot be deduced from the results obtained on a priori equivalent contacts.

The experimental determination of the Er-Ga-As phase diagram confirms the thermodynamical stability of the heavy rare-earth monoarsenides on GaAs prepared under an As vapor. The molecular beam epitaxy of ternary phases lattice-matched to GaAs such as Sc0.2Yb0.8As and Sc0.3Er0.7As allows one to suppress the appearance of mosaic spread and a χmin value as low as 1.5% was measured on these very high quality layers. The quality of the GaAs overlayers has to be improved, but quite good lattice-matched [Sc0.2Yb0.8As, Sc0.3Er0.7As] superlattices were grown on GaAs.

Strained epitaxial heterostructures yield attractive optoelectronic properties for laser diodes and optical amplifiers. Using various characterization techniques consisting of continuous and time resolved photoluminescence, X-ray diffraction, and transmission electron microscopy, the authors demonstrate the importance of the growth temperature on the relaxation of strained superlattices (SL). By lowering the growth temperature, high quality highly strained SL layers could be obtained.< >

Strained epitaxial heterostructures yield attractive optoelectronic properties for laser diodes and optical amplifiers. Using various characterization techniques consisting of continuous and time resolved photoluminescence, X-ray diffraction, and transmission electron microscopy, the authors demonstrate the importance of the growth temperature on the relaxation of strained superlattices (SL). By lowering the growth temperature, high quality highly strained SL layers could be obtained

Successful growth by molecular beam epitaxy of YbSb2 (010) single crystal films on GaSb(001) has been demonstrated. The YbSb2 films have a room temperature resistivity equal to 40 muOMEGA cm. YbSb2 has a basal plane rectangular (but almost square) and nearly lattice matched to GaSb. The memory of the GaSb(001) surface orientation is transferred to the YbSb2 surface films, avoiding the formation of inversion domains in the GaSb overlayers. The effects of the lattice mismatches in the basal plane and in the growth direction are discussed.

Despite its excellent transport properties, the low value of the Schottky barrier height on n- type InP (0.43 eV) prevents its use in electronic applications. A new InP lattice- matched material (GaPSb with 65% Sb) has been grown for the first time by gas source molecular beam epitaxy and studied. The material gap is 0.9 eV and the gold Schottky diode reaches 0.6 eV on this compound. This is the highest barrier ever reported on InP lattice-matched materials which do not contain aluminum. Continuous and picosecond luminescence results show that the GaPSb/InP is a type II heterostructure with ΔEc=50 meV at 4 K.

Solid-state interactions of Ni thin films on (111) GaAs and (111) AlAs were investigated using transmission electron microscopy. We show that the experimental determination of the Ni-Ga-As and Ni-Al-As ternary phase diagrams, and the accurate determination of the atomic composition and crystalline structure of the various ternary solid solutions are absolutely required to understand the x-ray and electron diffraction patterns, and thus identify the compounds in the reacted layers and explain the different steps of the reactions. For this purpose, we report the results obtained on three typical samples, where hexagonal superstructured ternary phases have been observed.