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Investigations of the sputtering of films of the PbSnTe ternary solid solution with 0 ≤ x ≤ 1 in RF high-density low-pressure inductively coupled argon plasma have been performed. The effect of a constant sputtering rate with variation in the composition of the semiconductor solid solution for (111)-oriented films with x < 0.6 and of a sputtering rate decrease with the appearance of (100)-oriented crystallites at x > 0.6 is found. The results are analyzed in the context of a model of ternary alloy sputtering based on the Sigmund solid sputtering theory when taking into account the sublimation energies of binary compounds that constitute a solid solution. [ABSTRACT FROM AUTHOR]

We investigated the magnetotransport properties of n- and p-type films of Pb1-xEuxTe grown by molecular beam epitaxy, with Eu concentrations close to the Metal-Insulator transition. The n-type sample shows a negative magnetoresistance which magnitude increases continually as the temperature is lowered. On the other hand, for the p-type sample, a negative magnetoresistance can be observed only for temperatures below 7 K. Comparing the magnetoresistance of both samples we show that the scattering mechanism should have a different origin. [ABSTRACT FROM AUTHOR]

The transport properties of p-type Pb1− xEu xTe epitaxial layers were studied as a function of Eu content, temperature, and magnetic field. The low-temperature hole mobility is drastically reduced when the Eu concentration is increased from 0 to 6%, while the hole concentration remains almost constant. A metal-insulator transition was observed for x ≈ 0.04, which is probably induced by the disorder caused by the introduction of Eu. For temperatures down to 10 K, only positive magnetoresistance has been observed at low magnetic fields. An anomalous behavior of the resistivity as a function of temperature has been detected for a Eu content about 5%, which is attributed to the resonance between the localized Eu 4 f level and the valence band maximum. [ABSTRACT FROM AUTHOR]

It is shown that the energies of radiative transitions between the ground states of electrons and holes for high-quality deep PbTe quantum wells at low temperatures are described well within the framework of the two-band model with regard to the nonparabolicity, strong anisotropy, and multivalley character of the band structure and also uniaxial deformation, that is present in the heterostructure. For a two-dimensional system, the temperature coefficient of the variation of the forbidden band gap decreases with decreasing well width, which is explained by a weakening of the electron–phonon interaction. © 2002 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

Mn ions were implanted in p-type cubic GaN at doses from 0.6 to 2.4×1016 cm-2 at 200 keV energy. A 200-nm-thick epitaxial layer, grown by molecular beam epitaxy on GaAs(001) substrate, is used for the Mn implantation. The Mn implanted samples were subjected to an annealing at 950 °C for 1–5 min. The structural quality of the samples was investigated by high resolution x-ray diffraction and Raman spectroscopy. The annealing procedure leads to a significant increasing of the crystalline quality of the samples. Hysteresis loops were observed for all cubic GaMnN annealed samples and ferromagnetism was detected up to room temperature. [ABSTRACT FROM AUTHOR]

Recently, several studies have been carried out on sol–gel films for optical applications, mostly motivated by the quickness and low cost of the film preparation process. In order to preserve the coherence properties of the light, improvements in the current quality of such films are necessary as well as appropriated techniques for structural characterization and quality control. X-ray specular reflectivity could be one of such techniques, but it is limited by the complexity of the internal nanostructure of the films. In this work, we have developed a procedure to extract the exact density profile of sol–gel films, and applied it to analyze a sol–gel derived Er[sub 2]O[sub 3] film. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Investigates the growth of Zn[sub 1-x]Mn[sub x]Te epilayer films grown by hot wall epitaxy on (001) GaAs substrates. Percentage concentration of manganese (Mn); Determination of Mn content by optical reflection and X-ray diffraction; Details on the relative tilt between the epilayer and the substrate.

We report here on the properties of topological crystalline insulator Pb0.5Sn0.5Te epitaxial films doped with bismuth at levels from 0% (undoped) to 0.15%. The undoped film exhibits a p-type character due to metal vacancies. As the doping level rises, the hole concentration reduces. At a level of 0.06%, the electrical character inverts to n-type and the electron density continues to increase for rising doping level up to 0.15%. This result demonstrates an effective extrinsic n-type doping of Pb0.5Sn0.5Te crystal with bismuth due to substitutional Bi atoms in metal sites. High-resolution x-ray diffraction and reciprocal space mapping show that fully relaxed high-quality films are obtained. A pristine (111) film surface is revealed after removal of the Te cover layer using a method combining Ar+ sputtering and thermal desorption. Angle-resolved photoemission spectroscopy (ARPES) data acquired at 30 K near the Γ ¯ point of the undoped film surface show a parabolic-like dispersion of the bulk valence band close to the Fermi level. Now, the ARPES data for a sample doped with 0.1% of Bi reveal that the chemical potential is shifted by 40 meV upwards in the direction of the conduction band. The ARPES results also indicate that there might be a discrepancy between surface and bulk chemical potential in the doped sample. This divergence suggests that Te atoms diffuse into the surface during the thermal process to desorb the protective layer, inverting the surface to p-type. [ABSTRACT FROM AUTHOR]

Presents a study that described x-ray diffraction in thin layers containing small randomly placed defects by means of the kinematical diffraction theory and optical coherence formalism. Calculation of both the diffracted intensity and angular distribution; simulation of double crystal and triple crystal x-ray diffractometry experiments; Application of the theory to experimental data obtained from diffractometry measurements of an epitaxial zinc-tellurium layer with mosaic structure.

Proposes the use of photoassisted epitaxial growth to enhance the substitutional doping in cadmium tellurium layers. Elements used as dopant sources in photoassisted molecular beam epitaxy; Investigation on the crystalline quality and electrical properties of the samples; Photoluminescence spectra obtained with the cadmium tellurum films.

A time-resolved optical pump-probe technique has been applied for studying the ultrafast dynamics in the magnetic semiconductor EuTe near the absorption band gap. We show that application of external magnetic field up to 6 T results in crossover from the inverse Faraday effect taking place on the femtosecond time scale to the optical orientation phenomenon with an evolution in the picosecond time domain. We propose a model which includes both these processes, possessing different spectral and temporal properties. The circularly polarized optical pumping induces the electronic transition 4 f 7 5 d 0 → 4 f 6 5 d 1 forming the absorption band gap in EuTe. The observed crossover is related to a strong magnetic-field shift of the band gap in EuTe at low temperatures. It was found that manipulation of spin states on intrinsic defect levels takes place on a time scale of 19 ps in the applied magnetic field of 6 T. [ABSTRACT FROM AUTHOR]

This work presents the investigation of the photoconductivity effect in undoped and doped Pb 0.5 Sn 0.5 Te epitaxial films, with bismuth (Bi) atoms, at temperatures of 80 and 300 K. The results indicate that the samples show negative photoconductivity effect (NPC) and persistent photoconductivity (PPC). A detailed study was performed on Pb 0.5 Sn 0.5 Te sample doped with 0.15 % Bi, which presented higher photoconductivity amplitude than the other samples, by performing Hall effect and photoconductivity measurements in the temperature range of 80–300 K under dark and illuminated conditions. Using Arrhenius model, trap activation energy was extracted and compared with energies found in literature. From the Hall measurement we found that the NPC effect observed is due to a decrease in the mobility when the sample is illuminated while the carrier concentrations are nearly unaltered. It was also found that Pb 0.5 Sn 0.5 Te:Bi presented photoconductivity response for a wide range of wavelengths, indicating that it is potentially interesting for application in optic sensor devices. • High quality lead tin telluride films were successfully doped with bismuth (Bi). • Lead tin telluride (Pb0.5Sn0.5Te) exhibited clear negative photoconductivity effect (NPC). • A complete transport properties profile is extracted for Bi doped Pb0.5Sn0.5Te. • Pb0.5Sn0.5Te Bi doped samples are sensitive to broadband light spectra. [ABSTRACT FROM AUTHOR]

Magnetoresistance measurements were performed on a 30 nm-thick SnTe quantum well (QW) grown by molecular beam epitaxy on the BaF2 substrate in the temperature range of 1.9–50 K. The weak antilocalization (WAL) effect was observed at low temperatures and low magnetic fields as a result of the strong spin–orbit coupling present in the QW. Using the Hikami–Larkin–Nagaoka equation, we analyzed the experimental data and found that the WAL effect is not purely 2D but composed of 2D and 3D channels that exist within the QW structure. The spin–orbit and phase coherence mechanisms are also extracted, and a general view of the transport properties of the QW is also provided. [ABSTRACT FROM AUTHOR]

Hybrid surface modification involving plasma immersion ion implantation (PIII) and ion nitriding has been attempted. DC cathode nitrogen glow discharges with 600–1000 V, 50–300 mA were typically obtained using the sample support as the cathode and the vacuum chamber as the anode. In this mode, sample temperatures of 500–600 °C can be reached easily while PIII at 10 kV, 50 μs and 400 Hz alone can provide about 300 °C heating. Combining these two highly conformal treatments and achieving high temperature, high efficiency three dimensional ion implantation is our objective. X-ray diffractions (XRD and high resolution XRD in the glancing mode) showed effects of ion nitriding in the AISI 304 stainless steel samples surface which indicate very thick nitrided layer, especially when operating the glow discharge in the low pressure but with high temperature nitriding mode. Auger electron spectroscopy and microhardness measurements confirmed nitriding in the sample surface. The hybrid treatment (PIII/ion nitriding) is expected to improve further these surfaces. [Copyright &y& Elsevier]

Recently, a significant amount of studies have been carried out on sol–gel films for optical applications, mostly motivated by the quickness and low cost of the film preparation process. Overcoating films of different density and thickness can produce waveguides for visible light as well as for X-rays. In order to preserve the coherence properties of the guided light, improvements in the current quality of the films are necessary as well as an appropriated technique for structural characterization and quality control. X-ray specular reflectivity can be such a technique, but it is limited by the complexity of the internal nanostrutucture of the films. In this work, we have developed a procedure to fit the specular reflectivity and extract the exact density profile of sol–gel films. It is applied to analyze a single compound film produced from a sol–gel of Er2O3 nanoparticles. It correlates the density variations and roughness with the steps of the preparation process. Moreover, we have also characterized an X-ray waveguide of Er2O3/TiO2/Er2O3 and theoretically optimized its structure to demonstrate the effects of density floating and roughness on the waveguidance efficiency. [Copyright &y& Elsevier]

Sponge-like and columnar porous silicon (PS) were prepared from p- and n-type (100) monocrystalline silicon wafers using different anodization conditions (hydrofluoric acid concentration, current density and anodization time) and then implanted with nitrogen by plasma immersion ion implantation (PIII). The effect of the implantation and of the compounds formed was analyzed by measuring the reflectance of the implanted samples for wavelengths between 220 and 800 nm. A reduction in reflectance in the ultraviolet (UV) region of the spectrum was observed for polished Si samples and for all kinds of PS samples. Increased UV-induced photoluminescence in these samples caused by the increase in absorption in the UV region is expected. [Copyright &y& Elsevier]

In this article, we report on structural and magnetic properties of cubic GaN epitaxial layers implanted with Fe ions and subsequently subjected to thermal annealing. The epitaxial quality of the layers was studied by X-ray diffraction rocking curves (ω-scans) and Raman spectroscopy. The results show that the implantation damages the crystal structure producing an expansion of the lattice parameter in the implanted region. These damages are partially removed by the thermal treatment. Room temperature ferromagnetism is observed for the sample implanted with a dose of 1.2 ×1016cm-2, while samples implanted with 2.4 ×1016 cm-2 show a coexistence of ferromagnetism and paramagnetism due to disperse Fe3+. Thermal annealing changes these magnetic properties. For the low dose sample, the ferromagnetism is converted into paramagnetism while for the high dose we observed an enhancement of the ferromagnetic contribution characterized by a super-paramagnetism behavior attributed to Fe-based particles. [ABSTRACT FROM AUTHOR]

We investigated the photoconductivity effect observed in a p-type SnTe quantum well in the temperature range of 1.9–100 K. The negative photoconductivity effect is observed for temperatures below 4 K, and it is strongly dependent on the light wavelength. A systematic analysis of the photoconductivity indicates that the origin of the negative photoconductivity is not related to the topological surface states but rather to the reduction of carrier mobility when the SnTe quantum well is illuminated with energies above 2 eV. [ABSTRACT FROM AUTHOR]

We investigate here the magneto-transport properties of a 10 nm-wide p -type PbTe single quantum well doped with BaF 2 as a function of temperature in the presence and absence of infrared light. Magnetoresistance measurements indicated the presence of Shubnikov-de Haas oscillations that are slightly altered at illuminated conditions. The fast Fourier transform analysis showed that, in dark conditions, the electrical transport occurs mainly via confined states derived from the longitudinal valley, while transport through the oblique valley is enhanced when light is switched on. Detailed analysis provided a full description of the transport properties including cyclotronic masses, Landé g -factors, and Rashba splitting. • Clear SdH oscillations observed in p-type PbTe QW. • Two close FFT peaks are attributed to Rashba spin-splitting of the longitudinal valley. • Multivalley transport is enhanced by infrared illumination. • Determination of Cyclotronic masses, Landé g -factors and Rashba splitting energy. [ABSTRACT FROM AUTHOR]