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A variety of detoxification methods have been utilized for the treatment of heroin withdrawal before individuals begin long-term opiate-free and naltrexone programs. While methadone in decreasing doses is still widely used for detoxication procedures, rapid and ultra-rapid protocols including clonidine and opiate receptors antagonists have been proposed. This study compares the efficacy of different detoxification methods and investigates possible changes in naltrexone compliance. Ninety-eight heroin-addicted individuals were studied to evaluate withdrawal symptoms, craving, mood, urine toxicologic screens, and drop-out rate during therapy with: Group A: clonidine only (5 days); Group B: clonidine, oxazepam, baclofen, and ketoprofene with naloxone and naltrexone (2 days); and Group C: methadone in decreasing doses (10 days). Naltrexone compliance and relapse rates were evaluated during a 6-month follow-up period. Rapid detoxification with opiate antagonists (Group B) induced slight and transient withdrawal symptoms, and resulted in a significantly lower percentage of heroin catabolites in urine controls during the detoxification procedure, lower negative and positive craving, less mood problems, and higher compliance in extended naltrexone treatment. In comparison with clonidine only (Group A) and methadone (Group C), the early use of naltrexone during detoxification in combination with benzodiazepines and clonidine facilitated extended naltrexone acceptance and improved the recovery outcome in outpatients.

Research was conducted to examine the calculate with very high accuracy the lattice constant of Ga(sub 1-x)Al(sub x)Sb layers grown on GaSb by molecular beam epitaxy and to calculate the Al molar fraction of the Ga(sub 1-x)Al(sub x)Sb alloys viva Rutherford backscattering spectrometry and reflection high-energy electron diffraction. Results demonstrate the possibility of verifying Vegard's law for the epitaxial system.

Zn-diffused InP layers were prepared using a sealed tube method. The substrates used were S- and Zn-doped InP crystals. The findings indicate a very sharp diffused/virgin interface in the S-doped crystal and that the diffuse layers are lattice contracted. Moreover, the maximum strain close to the surface is not dependent on the diffusion time and the thickness of the diffused layer increases with time.

Use of x-ray standing-wave methods and high-resolution x-ray diffraction to investigate lattice distortions caused by the implantation of Fe ions in InP semi-insulating crystals reveals that the thickness of the disturbed layer and the lattice strain, including static damage, increase directly with an increase in implantation dose. The investigation also yields information on the damage and strain in the surface layer. This helps distinguish various distortion profiles that provide the kinematical diffraction curve.

A systematic analysis of damage annealing and Fe implantation in n-doped indium phosphide (InP) using chemical, structural and electrical measurement techniques reveals that Fe implantation induces semi-insulating layers in InP. Application of high Fe doses for compensating n+ doping leads to amorphization of the InP. The resistivity values of the n-doped InP substrates exceed 2 times 10 to the 7th power ohms cm, indicating complete compensation and superior crystal quality. Two radically distinct annealing properties are seen depending on the presence or lack of an amorphous layer.

The effects of As incorporation on deviations from Vegard's law in A1GaSb are described.

Research was conducted to examine the interband optical properties of molecular-beam epitaxially grown GaAs(sub 1-x)Sb(sub x) on GaAs substrates. The complex dielectric functions and the interband critical point energies, which are important not only in optical characterization and engineering of more complex heterostructures but also in achieving band structure parameters versus x, were provided. The analytical dependence of the critical point energies versus x allowed the interpolation of the dielectric functions and the optical functions for any composition x

In this work we study the properties of energy levels of the two-dimensional quantum system composed by wetting layers and thin capping layers in low density InAs/InGaAs quantum dot structures, that can be used as single photon sources at the fiber-optic wavelength of 1.3 μm. We show how, thanks to the low density of quantum dots, x-ray characterization of structures allows to extract thicknesses and compositions of the InAs wetting layer and the quantum well formed by the InGaAs capping layer, resulting in substantial deviations from the simplified picture of a wetting layer consisting of a 1.6 monolayer thick InAs square well. The agreement between model calculations of quantum confined energy levels based on x-ray data and photoluminescence peak energies substantiates the validity of this calculation, that also allows to investigate on carrier localization. The increase in In composition in the InGaAs capping layer results in reduced localization of heavy holes in the wetting layer, that are pushed into the InGaAs quantum well, while the electron, being already strongly delocalized in the quantum well, is relatively less affected. We discuss consequences on carriers' overlap in the wetting layer and on spatial separation between wetting layer and quantum dot carriers and we consider implications for control of properties of quantum dot structures suitable as single photon sources in the telecommunication windows. [ABSTRACT FROM AUTHOR]

In this work, we present a study of InAs quantum dots deposited on InGaAs metamorphic buffers by molecular beam epitaxy. By comparing morphological, structural, and optical properties of such nanostructures with those of InAs/GaAs quantum dot ones, we were able to evidence characteristics that are typical of metamorphic InAs/InGaAs structures. The more relevant are: the cross-hatched InGaAs surface overgrown by dots, the change in critical coverages for island nucleation and ripening, the nucleation of new defects in the capping layers, and the redshift in the emission energy. The discussion on experimental results allowed us to conclude that metamorphic InAs/InGaAs quantum dots are rather different nanostructures, where attention must be put to some issues not present in InAs/GaAs structures, namely, buffer-related defects, surface morphology, different dislocation mobility, and stacking fault energies. On the other hand, we show that metamorphic quantum dot nanostructures can provide new possibilities of tailoring various properties, such as dot positioning and emission energy, that could be very useful for innovative dot-based devices. [ABSTRACT FROM AUTHOR]

This paper presents a detailed study of structure, morphology, and magnetic properties in FePt thin films epitaxially grown on MgO(100) at intermediate temperatures (≅380 °C). It focuses on the effects obtained by in situ annealing the FePt films after deposition. We have demonstrated that the annealing allows one to complete the ordering, thus obtaining an epitaxial L10-FePt film with large perpendicular anisotropy (up to 3×107 erg/cm3) and high perpendicular squareness and remanence ratio (both higher than 0.85). At the same time, we have found a peculiar morphology evolution by increasing the annealing time: the interconnected mazelike grains evolve towards interconnected dotlike grains of reduced size (down to 10 nm). Due to the interconnection at the grains basis, the increase in the film perpendicular coercivity with the annealing process is moderate (up to 4.1 kOe), leading to an increasing anisotropy/coercivity ratio with the annealing time. As a further step towards the understanding of the properties evolution with annealing, we have investigated the magnetic domain pattern and analyzed the domain-period dependence on the anisotropy constant in comparison with the behavior expected by the Kooy–Enz theory [C. Kooy and U. Enz, Philips Res. Rep. 15, 7 (1960)]. The main magnetic properties and reduced grain size obtained after the in situ annealing are promising to realize perpendicular recording media with reduced bit size, high thermal stability, and suitable switching field. [ABSTRACT FROM AUTHOR]

We report a detailed study of InAs/GaAs quantum dot (QD) structures grown by molecular beam epitaxy with InAs coverages θ continuously graded from 1.5 to 2.9 ML. The effect of coverage on the properties of QD structures was investigated by combining atomic force microscopy, transmission electron microscopy, x-ray diffraction, photoluminescence, capacitance-voltage, and deep level transient spectroscopy. In the 1.5–2.9 ML range small-sized coherent QDs are formed with diameters and densities that increase up to 15 nm and 2×1011 cm-2, respectively. For θ>2.4 ML large-sized QDs with diameters of 25 nm and densities ranging from 2×108 to 1.5×109 cm-2 coexist with small-sized QDs. We explain the occurrence of large-sized QDs as the inevitable consequence of ripening, as predicted for highly lattice-mismatched systems under thermodynamic equilibrium conditions, when the coverage of the epitaxial layer exceeds a critical value. The fraction of ripened islands which plastically relax increases with θ, leading to the formation of V-shaped defects at the interface between QDs and upper confining layers that propagate toward the surface. Island relaxation substantially affects the properties of QD structures: (i) free carrier concentration is reduced near the QD plane, (ii) the QD photoluminescence intensity is significantly quenched, and (iii) deep levels show up with typical features related to extended structural defects. [ABSTRACT FROM AUTHOR]

The Al0.4Ga0.6Sb/GaSb/Al0.4Ga0.6Sb quantum well (QW) structures were grown by a molecular beam epitaxy on the GaSb substrates at different growth temperatures (Tg) and with different Sb4/Ga beam equivalent pressure ratios (BEPR) and were studied using high-resolution x-ray diffraction, photoluminescence (PL), and transmission electron microscopy. The x-ray diffraction analysis showed that the AlGaSb/GaSb interfaces have smooth Al composition profiles with graded region thicknesses in the range of 0.83 nm–2.17 nm, depending upon the growth conditions; the normal interfaces are generally sharper than the inverse ones. The low-temperature PL spectra from QWs show relatively broad peaks and energies of the peak emission that can be related to the growth parameters. Good agreement was obtained between the PL peak energies and the transition energies calculated using a QWs model that takes into account the one-dimensionally graded confining potential for describing the experimentally determined Al composition profiles. The interface broadening can be due to Al and Ga segregation, Al diffusion, or Al and Ga intermixing. The broadening increases with the growth conditions that enhance the surface mobility of group-III species, such as high Tg and low V/III BEPRs. The relatively large full widths at half maxima of the PL features were attributed to the Al composition fluctuations in the barriers, instead of the well thickness ones. [ABSTRACT FROM AUTHOR]

Ga[sub 0.6]Al[sub 0.4]Sb/GaSb single-quantum-well structures grown by molecular-beam epitaxy on GaSb substrates with different well thicknesses, have been studied by high-resolution x-ray diffraction and x-ray standing-wave methods. By fitting the diffraction curves, thickness, composition, and the static Debye–Waller factor were obtained for each layer of the structures. The analysis of the angular dependence of the yield of photoelectrons emitted by the x-ray standing-wave field in the range of the dynamical x-ray diffraction was used for selecting the most appropriate set of layer parameters among those which gave virtually identical fittings of the diffraction curves. Relatively broadened GaAlSb/GaSb interfaces were found in all of the samples. This result was confirmed by high-resolution transmission electron microscopy investigation of one of the samples. The effect of the surface degradation due to the chemical reaction with the atmosphere of the free surface of the upper Ga[sub 0.6]Al[sub 0.4]Sb layer was considered. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The properties of energy levels of the two-dimensional quantum system composed by wetting layers and thin capping layers in low density InAs/InGaAs quantum dot structures are analyzed, which are used as single photon sources at the fiber-optic wavelength of 1.3 [micro]m. The consequences on carriers' overlap in the wetting layer and on spatial separation between wetting layer and quantum dot carriers are discussed and the implications for control of properties of quantum dot structures suitable as single photon sources in the telecommunication windows are considered.

Presents information on a study which obtained the composition of several gallium-aluminum-antimony epitaxial layers of different thicknesses grown by molecular beam epitaxy on gallium-antimony using high resolution x-ray diffraction. Experimental details; Results and discussion; Conclusions.

Studies the atomic arrangement within the substituted sublattice in III-V solid solutions using X-ray diffuse scattering experiments. Theory of X-ray diffuse scattering; Experimental methods; Results of the study.

Presents an optical study of strained and relaxed epitaxial In[subx]Ga[1-x]As on gallium arsenide. Method of the study; Results and discussion; Conclusion.