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The study of the magnetic properties of Co nanoparticles (with an average diameter of 10.3 nm) grown using a gas-phase aggregation source and embedded in Au and V matrices is presented. We investigate how the matrix, the number of embedded nanoparticles (counted by coverage percentage), the interparticle interactions and the complex nanoparticles/matrix interface structure define the magnetic properties of the studied systems. A threshold coverage of 3.5% of a monolayer was found in both studied systems: below this coverage, nanoparticles behave as an assembly of independent single-domain magnetic entities with uniaxial anisotropy. Above the threshold it is found that the magnetic behavior of the systems is more matrix dependent. While magnetic relaxation and Henkel plots measurements stress the importance of the dipolar interactions and the formation of coherent clusters in the case of the Au matrix, the magnetic behavior of cobalt clusters embedded in the vanadium matrix is explained through the formation of a spin glass-like state at the V-Co interface that screens the magnetic interactions between NPs. © the Owner Societies 2013., Work was supported by the Spanish Ministerio de Economía y Competitividad under projects MAT2011-29194-C02-02, MAT2011-27470-C02-02, MAT-2007-66181, MAT2008-06765-C02, MAT2008-06517-C02-01, CSD2007-00041 (NANOSELECT), CSD2008-00023 (FUNCOAT), CSD2009-00013, CSD2007-00010, FIS2008-06249 (Grupo Consolidado), CAM grant S2009/MAT-1726, Santander-UCM grant GR35/10-A-910571 and European Commission NMP3-SL-2008-214107. M.R. acknowledges the FPI grant from the Spanish Ministerio de Economía y Competitividad.

In this research, an ion milling equipment was used to elaborate nanoparticles from Cu-Zn-Al alloys with shape memory effect. Two different compositions were used, target A: 75.22Cu-17.12Zn-7.66Al at % with an Ms of -9 °C and target B: 76.18Cu-15.84Zn-7.98Al with an Ms of 20 °C. Nanoparticles were characterized by High Resolution Transmission Electron Microscopy, Electron Diffraction and Energy Dispersive X-ray Spectroscopy. The obtained nanoparticles showed a small dispersion, with a size range of 3.2-3.5 nm. Their crystal structure is in good agreement with the bulk martensitic structure of the targets. In this sense, results on morphology, composition and crystal structure have indicated that it is possible to produce nanoparticles of CuZnAl shape memory alloys with martensitic structure in a single process using Ion Milling.

El tacto vaginal es un procedimiento que se utiliza con mucha frecuencia durante la asistencia a la mujer gestante tanto en el periodo del parto como durante el seguimiento del embarazo. La exploración vaginal, es una de las técnicas diagnósticas fundamentales en el comienzo y el progreso del parto. El objetivo de nuestro trabajo es desarrollar un protocolo, teniendo en cuenta las recomendaciones de la evidencia científica, y por otro lado reducir el riesgo de infección intraparto, materna y neonatal. Los beneficios que esperamos obtener con la elaboración de este protocolo son, por un lado, la mejora de la calidad de los cuidados enfermeros en la aplicación del tacto vaginal, y por otro lado la disminución de complicaciones durante la realización del mismo. The pelvic exam is a procedure widely used for assisting pregnant women in both the delivery period and sometimes for the monitoring of pregnancy. Vaginal examination is one of the key diagnostic in the onset and progression of labor. The aim of our work is formalize this action to standardize the performance, taking into account the recommendations of the scientific evidence, and secondly to reduce the risk of intrapartum infection, maternal and neonatal mortality. The benefits expected from the development of this protocol on the one hand, improving the quality of nursing care in the application of vaginal examination, and secondly the reduction of complications during fulfillment.

Voltage-gated sodium channels are responsible for action potential initiation and propagation in electrically excitable cells. In this study, we used biochemical, immunohistochemical and quantitative immunoelectron microscopy techniques to reveal the temporal and spatial expression of the Na(v)1.2 channel subunit in granule cells of cerebellum. Using histoblot, we detected Na(v)1.2 widely distributed in the adult brain, but prominently expressed in the cerebellum. During postnatal development, Na(v)1.2 mRNA and protein were detected low during the first and second postnatal week, increased to P15 and then continue to decrease until adult levels. At the light microscopic level, Na(v)1.2 immunoreactivity concentrated in the molecular layer of the cerebellar cortex. Using immunofluorescence, Na(v)1.2 colocalised with VGluT1, but not with VGluT2, demonstrating that the subunit was preferentially present in parallel fibre axons and axon terminals. At the electron microscopic level, Na(v)1.2 immunoparticles were exclusively detected at presynaptic sites in granule cell axons and axon terminals of granule cells, with occasional clustering in their axon initial segment. This was demonstrated using quantitative immunogold analysis. In the axon terminals, the distribution of Na(v)1.2 was relatively uniform along the extrasynaptic plasma membrane and never detected in the active zone. We could not find detectable levels of Na(v)1.2 at postsynaptic elements of granule cells or other cerebellar cell types. The present findings show a polarised distribution of Na(v)1.2 along the neuronal surface of granule cells and suggest its primary involvement in the transmission of information from granule cells to Purkinje cells.

Alternately-strained-layer of (GaAs)n(GaP)m(GaAs)n(InP)m, superlattices with n = 10, 90 and m = 2 monolayers, have been characterized by X-ray diffraction and high-resolution transmission electron microscopy. The heterostructures were grown by atomic layer molecular beam epitaxy on GaAs semi-insulating substrates at a substrate temperature of 710K. All the structures were coherent with the substrate and there is an effective compensation of the strains due to GaP and InP layers. X-ray diffraction and high-resolution electron microscopy analysis indicate a high crystalline quality with layers thickness deviations of ± 1 monolayer from the designed value.

In mouse hippocampal CA1 pyramidal neurons, the activity of synaptic small-conductance Ca2+-activated K+ channels type 2 (SK2 channels) provides a negative feedback on N-methyl-d-aspartate receptors (NMDARs), reestablishing Mg2+ block that reduces Ca2+ influx. The well-established role of NMDARs in ischemia-induced excitotoxicity led us to test the neuroprotective effect of modulating SK2 channel activity following cerebral ischemia induced by cardiac arrest and cardiopulmonary resuscitation (CA/CPR). Administration of the SK channel positive modulator, 1-ethyl-benzimidazolinone (1-EBIO), significantly reduced CA1 neuron cell death and improved CA/CPR-induced cognitive outcome. Electrophysiological recordings showed that CA/CPR-induced ischemia caused delayed and sustained reduction of synaptic SK channel activity, and immunoelectron microscopy showed that this is associated with internalization of synaptic SK2 channels, which was prevented by 1-EBIO treatment. These results suggest that increasing SK2 channel activity, or preventing ischemia-induced loss of synaptic SK2 channels, are promising and novel approaches to neuroprotection following cerebral ischemia.

The use of Ga-Au alloys as metal catalysts for the growth of SiGe nanowires has been investigated. The grown nanowires are cylindrical and straight, with a defect-free crystalline structure, sharp nanowire-droplet interfaces and an almost constant Ge atomic fraction throughout all their length. These features represent significant improvements over the results obtained using pure Au.

SiGe nanowires of different Ge atomic fractions up to 15% were grown and ex-situ n-type doped by diffusion from a solid source in contact with the sample. The phenomenon of dielectrophoresis was used to locate single nanowires between pairs of electrodes in order to carry out electrical measurements. The measured resistance of the as-grown nanowires is very high, but it decreases more than three orders of magnitude upon doping, indicating that the doping procedure used has been effective.

In deformed CaO crystals, the predominant optical-absorption band at 270 nm and the corresponding luminescence band at 450 nm have been investigated. The absorption coefficient increases linearly with deformation up to \ensuremath{\sim}5% whereas the luminescence intensity saturates earlier. Thermal annealing indicates that appreciable decrease in the absorption begins at \ensuremath{\sim}600 K. In contrast, the luminescence intensity diminishes very rapidly at temperatures not much above room temperature. Time-resolved luminescence indicates that the 450-nm band is composed of two bands: a 475-nm band with lifetimes of 3 ns and \ensuremath{\sim}10 \ensuremath{\mu}s, and a 440-nm band with a lifetime of \ensuremath{\sim}1 ms at room temperature. In a test for laser action no optical gain was observed in a deformed CaO crystal.

Thermochemical reduction at high temperatures has been performed on chromium-doped lanthanum magnesium aluminate crystals. Analytical transmission-electron-microscopy and optical-absorption techniques were used to characterize the crystals. Copper impurities inherently present in the crystals began to aggregate and form Cu-rich particles at 1500 K near the surface region. Below 1870 K there was no evidence of chromium precipitates being formed. However, Cr-rich particles were formed at 2020 K. The distribution of the precipitates was very inhomogeneous and the precipitates were also concentrated near the surface region.

A series of amphiphilic triblock copolymers, poly[oligo(ethylene glycol) methacrylate]x-block-poly(ε-caprolactone)-block-poly[oligo(ethylene glycol) methacrylate]x, POEGMACo(x), were synthesized. Formation of hydrophobic domains as cores of the micelles was studied by fluorescence spectroscopy. The critical micelle concentrations in aqueous solution were found to be in the range of circa 10⁻⁶ M. A novel methodology by modulated temperature differential scanning calorimetry was developed to determine critical micelle temperature. A significant concentration dependence of cmt was found. Dynamic light scattering measurements showed a bidispersed size distribution. The micelles showed reversible dispersion/aggregation in response to temperature cycles with lower critical solution temperature between 75 and 85 °C. The interplay of the two hydrophobic and one thermoresponsive macromolecular chains offers the chance to more complex morphologies. The authors are indebted to Francesç Catala, from Mettler-Toledo, for valuable discussions. The authors are grateful to LABMET, TEM Laboratory associated to the Comunidad Autónoma de Madrid network and Mr. J. González-Casablanca for his cooperation with the TEM images. The authors would like to thank the Plan Nacional IþDþI (Ministerio de Ciencia e Innovación) for financial support (MAT2009-09671) as well as the Comunidad Autónoma de Madrid for the funding through IþD Program (S0505/MAT-0227).

ZnO/MnOx nano-thin multilayers are fabricated by pulsed laser deposition with a sectioned target or “cake” technique. Structure and magnetic properties are measured, finding a magnetic signal that scales better with the number of interfaces than with the film volume, and an interlayer interdiffusion that happens at remarkably low film growth temperatures., The authors gratefully acknowledge financial support from CSIC under projects CSIC: PIF CSIC 2006-50F0122, CSIC 2007-50I015 and from the Spanish “Ministerio de Ciencia y Tecnología” MAT2008-06330 and MAT2007-68845-C02-01. TEM work has been done at the LABMET, associated to the network Red de Laboratorios of the CAM.

SiGe nanowires were grown by the vapor-liquid-solid method using a low pressure chemical vapor deposition reactor and different flows of the GeH4 and Si2H6 gas precursors. The morphology of the nanowires was studied by field emission scanning electron microscopy, and the length, diameter and density of nanowires were determined. Their structure and crystallinity were analyzed by transmission electron microscopy and its related techniques. Energy dispersive X-ray emission of individual nanowires as well a Raman spectroscopy were used to determine their composition and to analyze its homogeneity.

Group IV (Si or Ge) nanocrystals embedded in a dielectric medium have potential applications in electronic and optoelectronic devices. Previous results indicate that low pressure chemical vapour deposition (LPCVD) of amorphous discontinuous SiGe films in SiO2 on top of Si-substrates and their subsequent crystallization permit to obtain a homogeneous distribution of SiGe nanocrystals, the process being fully compatible with CMOS technology [1]. In this work, Si-Ge-O films were deposited by LPCVD and furnace annealed at temperatures from 600 to 1100 oC for times up to 1 hour in a N2 atmosphere to segregate the expected excess of Si and/or Ge in the form of nanocrystals embedded in an oxide matrix. High-resolution transmission electron microscopy (HREM) and electron-diffraction pattern simulation by fast Fourier transform was used to analyze the crystal structure and distribution of the nanoparticles and their stability under in situ electron irradiation. TEM observation and electron beam irradiation were

Caregiving for the elderly has been linked to mental and physical problems in those providing the care. The aim of this study is to analyze the effects of leisure on caregiver's burden and mental health. Drawing on the stress and coping model, 134 caregiver/care-recipient dyads were assessed. In addition to caregivers' perception of their leisure time, social support, burden and mental health, care-recipients' functional and mental status were also measured. The results of a set of hierarchical regression analyses showed that caregivers' perceptions of their leisure time were significantly negatively related to burden and mental health problems (p

Multilayer structures with five periods of amorphous SiGe nanoparticles/SiO2 layers with different thickness were deposited by Low Pressure Chemical Vapor Deposition and annealed to crystallize the SiGe nanoparticles. The use of grazing incidence RBS was necessary to obtain sufficient depth resolution to separate the signals arising from the individual layers only a few nm thick. The average size and areal density of the embedded SiGe nanoparticles as well as the oxide interlayer thickness were determined from the RBS spectra. Details of eventual composition changes and diffusion processes caused by the annealing processes were also studied. Transmission Electron Microscopy was used to obtain complementary information on the structural parameters of the samples in order to check the information yielded by RBS. The study revealed that annealing at 900 °C for 60 s, enough to crystallize the SiGe nanoparticles, leaves the structure unaltered if the interlayer thickness is around 15 nm or higher.

The structure of amorphous and crystalline SiGe nanoparticles, embedded in a dielectric medium, SiO2, and its stability under “in situ” electron beam irradiation is reported. High-resolution transmission electron microscopy and electron-diffraction pattern simulation by fast Fourier transform was used to analyze the crystal structure of the SiGe nanoparticles. Electron beam irradiation induces structural alternate order-disorder transitions in the nanoparticles for irradiation effects are mainly associated to the density of current. For irradiation with current densities < 7 A·cm-2 no effects are observed in the as-deposited amorphous samples, whereas in the crystallized samples, SiGe nanocrystals show higher stability and no effects are observed for irradiation densities of current < 50 A·cm-2. Irradiation with densities of current greater than these thresholds cause consecutive amorphous-crystalline or crystalline-amorphous structure transitions respectively for both amorphous and crystallized nanoparticles. A hexagonal structure is proposed for those nanocrystals obtained after irradiation in the as deposited amorphous samples.

3 pags. ; 4 figs., Self-aligned silver nanocolumns embedded in amorphous Al₂O₃ matrix are produced by alternate pulsed laser deposition at room temperature in a single step process. The morphology and the spatial distribution have been investigated by standard, high resolution, and scanning transmission electron microscopy. Polycrystalline nanocolumns having diameters close to 3 nm and heights up to 7 nm are all oriented perpendicular to the substrate surface. The self-alignment of the nanocolumns is the consequence of the deposition of consecutive layers of Ag nanoparticles using the first layer as template for the ordered growth of the nanocolumns. Control over the density, diameter and height of the nanocolumns is achievable by tailoring the deposition sequence., This work was partially supported by TIC2002-03235, CICYT (Spain) and by ESP2002-04509-C04-01, and EU Network HPRN-CT-2002-00328.

Luminescent multilayers of SiGe nanocrystals embedded in an oxide matrix have been fabricated by Low Pressure Chemical Vapour Deposition of a-SiGe and SiO2 in a single run followed by a Rapid Thermal Annealing treatment. The diameter of the nanoparticles, the oxide interlayer thickness and the annealing conditions have been investigated in order to get the maximum intensity of the luminescence. The structures with small nanoparticles (3-4.5 nm) separated by thick oxide barriers (≈35 nm) annealed at 900 °C for 60 s yield the maximum intensity. These samples exhibit luminescence from 80 K to room temperature. An additional treatment at 450 °C in forming gas further increases the intensity of this luminescence.

As‐deposited iridium‐silicon interface structures have been characterized by cross‐section high‐resolution transmission electron microscopy. Iridium films were deposited by an e‐beam gun on (100) Si wafers heated at 200 °C during the deposition. A planar polycrystalline interfacial layer, 2–3 nm thick, was formed between the iridium and the silicon substrate. Thermodynamic calculations are presented which describe the development of the interfacial layer. Correlation between the observed structure and that proposed by thermodynamic calculations is discussed.

Amorphous SiGe/SiO2 multilayers with controlled thickness in the range of nanometers have been deposited by LPCVD at low temperature in a single multistep run. Continuous and discontinuous layers have been deposited. No intermixing between the SiGe and SiO2 layers has been observed. As-deposited and crystallized multilayers have been characterized by Raman spectroscopy, Cathodoluminescence and TEM. The luminescence emission is more intense in the discontinuous layers than in the continuous ones.

We report on the growth mechanism of ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}x}.$ Our study is based on an analysis of ultrathin ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}x}$ (YBCO) layers in c-axis-oriented ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}x}/{\mathrm{PrBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7}$ superlattices. We have found that the release of epitaxial strain in very thin YBCO layers triggers a change in the dimensionality of the growth mode. Ultrathin epitaxially strained YBCO layers with thickness below 3 unit cells grow in a block-by-block two-dimensional mode that is coherent over large lateral distances. Meanwhile, when the thickness increases and the strain relaxes, layer growth turns three-dimensional, resulting in rougher layers and interfaces.

We report the effects of epitaxial strain and deoxygenation on high quality $[{\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}x}(\mathrm{YBCO}{)}_{N}/{\mathrm{PrBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7}(\mathrm{PBCO}{)}_{5}{]}_{1000\mathrm{\AA{}}}$ superlattices, with $1lNl12$ unit cells. High-spatial-resolution electron energy loss spectroscopy shows that strained, fully oxygenated YBCO layers are underdoped. Irrespective of whether underdoping is induced by strain or deoxygenation, x-ray diffraction analysis shows that ${T}_{c}$ correlates directly with separation of the ${\mathrm{CuO}}_{2}$ bilayers.

5 pages, 3 figures.-- PACS nrs.: 81.16.Rf, 81.65.Cf, 68.35.B-, 68.37.Lp, 68.37.Ps, 68.47.Fg. We report on the production of nanoscale patterning on Si substrates by low-energy ion-beam sputtering. The surface morphology and structure of the irradiated surface were studied by atomic force microscopy (AFM) and high-resolution transmission electron microscopy (HRTEM). Under ion irradiation at off-normal incidence angle (~50°), AFM images show the formation of both nanoripple and sawtooth-like structures for sputtering times longer than 20 min. The latter feature coarsens appreciably after 60 min of sputtering, inducing a large increase in the surface roughness. This behaviour is attributed to the preferential direction determined on the substrate by the ion beam for this incidence angle, leading to shadowing effects among surface features in the sputtering process. Under irradiation at normal incidence, the formation of an hexagonal array of nanodots is induced for irradiation times longer than 2 min. The shape and crystallinity of the nanodots were determined by HRTEM. At this incidence angle, the surface roughness is very low and remains largely unchanged even after 16 h of sputtering. For the two angle conditions studied, the formation of the corresponding surface structures can be understood as the interplay between an instability due to the sputtering yield dependence on the local surface curvature and surface smoothing processes such as surface diffusion. Publicado

4 pags.; 4 figs.; OCIS Codes (130.3130) Integrated optics : Integrated optics materials (140.3390) Lasers and laser optics : Laser materials processing; (160.5690) Materials : Rare-earth-doped materials; (250.5230) Optoelectronics : Photoluminescence (160.4236) Materials : Nanomaterials (250.5590) Optoelectronics : Quantum-well, -wire and -dot devices., The potential of Ge nanoparticles (NPs) embedded in Al2O 3 with tunable effective optical bandgap values in the range of 1.0-3.3 eV to induce enhanced Er3+ light emission is investigated. We demonstrate nonresonant indirect excitation of the Er3+ ions mediated by the Ge NPs at room temperature. Efficient Er3+ light emission enhancement is obtained for Ge NPs with large effective optical bandgaps in the range of 1.85 to 2.8 eV. The coupled Ge NP-Er emission shows a negligible thermal quenching from 10 K to room temperature that is related to Er3+ de-excitation through thermally activated defect states. © 2014 Optical Society of America., This work has been financially supported by projects TEC2012-38901-C02-01, TEC2011-29120-C05-04, MAT2011-13333E, and P2009/ESP-1503 (Spain). J. M.-S. acknowledges support through the JAE-DOC-070/01 CSIC grant cofunded by FSE and J. T. from JCI grant JCI2009-05098.

3 pages, 3 figures., We report on the production of ordered assemblies of silicon nanostructures by means of irradiation of a Si (100) substrate with 1.2 keV Ar + ions at normal incidence. Atomic force and high-resolution transmission electron microscopies show that the silicon structures are crystalline, display homogeneous height, and spontaneously arrange into short-range hexagonal ordering. Under prolonged irradiation (up to 16 h) all dot characteristics remain largely unchanged and a small corrugation develops at long wavelengths. We interpret the formation of the dots as a result of an instability due to the sputtering yield dependence on the local surface curvature., This work has been partially supported by DGES (Spain) Grant Nos. MAT1999-0830-C03-01, MAT2000-0375-C02-02, and BFM2000-0006.

The structure of c-axis oriented [YBa2Cu3O7−(YBCO) N / PrBa2Cu3O7 (PBCO)M/1000Å superlattices with N ranging between 1 and 12 and M=5 unit cells, grown by high oxygen pressure sputtering on (100) SrTiO3 substrates, is analyzed by x-ray diffraction (XRD) and highresolution transmission electron microscopy (HREM). The XRD spectra refinement shows epitaxial strain for YBCO thickness below 4 unit cells. For larger YBCO layer thickness, stress relaxes and step disorder builds up. HREM observations show sharp and flat interfaces between substrate and superlattice stack. The only observable defects are isolated steps or a-axis oriented domains in relaxed samples. The results of both structural tools are compared.

Two amorphous compositions of the Co-B system, which present quite different magnetic behaviour, have been studied in the as-cast state and after low temperature annealings. The Co 80 B 20 amorphous alloy submitted to thermal treatments undergoes a primary crystallisation which transforms the material into a two phase system composed of nanocrystals of cobalt embedded in a Co-B amorphous matrix. The role of the cobalt grains on the magnetisation processes and the coercive field is analysed for temperature ranging from 77 to 300 K. It is found that the hardening effect of the grains diminishes on increasing the temperature. The large crystalline anisotropy of the Co grains as well as the magnetic state of the grain boundary which transmits the exchange interaction, are mainly responsible for the observed behaviour.

The use of Ga-Au alloys of different compositions as metal catalysts for the growth of abrupt SiGe/Si nanowire axial heterostructures has been investigated. The heterostructures grown in a continuous process by just switching the gas precursors, show uniform nanowire diameters, almost abrupt compositional changes and no defects between the different sections. These features represent significant improvements over the results obtained using pure Au.

SiGeO films were deposited by LPCVD using Si2H6, GeH4 and O2 as reactive gases and furnace annealed to segregate the excess of Ge in the form of nanocrystals embedded in a SiO2 matrix in a low temperature budget process fully compatible with current processing technologies. For low GeH4 partial pressures (4.8 mTorr) and a deposition temperature of 450 ?C, the deposited film consists of a SiO2 matrix incorporating Ge atoms, and no Ge oxides are detected. After annealing of the sample at a temperature of 600 ?C, quasi-spherical isolated Ge nanocrystals homogeneously distributed throughout the whole film thickness, with diameters ranging from 4.5 to 9 nm and an areal density of around 7 ? 1011 cm?2, are formed while the SiO2 matrix holds its original composition. Increasing the GeH4 partial pressure results in only a slight increase in the density of nanoparticles with no significant changes in their diameters and a matrix is formed by a mixture of Si and Ge oxides. A decrease in the deposition temperature results in very slow growth rates. Finally, increasing the annealing temperature causes no improvement in the sample characteristics, but a transformation of the matrix into a mixture of Si and Ge oxides takes place and Ge diffusion processes start to appear.

The luminescence emission of structures containing Ge nanocrystals embedded in a dielectric matrix obtained by dry and wet oxidation of polycrystalline SiGe layers has been studied as a function of the oxidation time and initial SiGe layer thickness. A clear relationship between the intensity of the luminescence, the structure of the sample, the formation of Ge nanocrystals and the oxidation process parameters that allows us to select the appropriate process conditions to get the most efficient emission has been established. The evolution of the composition and thickness of the growing oxides and the remaining SiGe layer during the oxidation processes has been characterized using Raman spectroscopy, x-ray diffraction, Fourier-transform infrared spectroscopy, Rutherford backscattering spectrometry and transmission electron microscopy. For dry oxidation, the luminescence appears suddenly, regardless of the initial SiGe layer thickness, when all the Si of the SiGe has been oxidized and the remaining layer of the segregated Ge starts to be oxidized forming Ge nanocrystals. Luminescence is observed as long as Ge nanocrystals are present. For wet oxidation, the luminescence appears from the first stages of the oxidation, and is related to the formation of Ge-rich nanoclusters trapped in the mixed (Si and Ge) growing oxide. A sharp increase of the luminescence intensity for long oxidation times is also observed, due to the formation of Ge nanocrystals by the oxidation of the layer of segregated Ge. For both processes the luminescence is quenched when the oxidation time is long enough to cause the full oxidation of the Ge nanocrystals. The intensity of the luminescence in the dry oxidized samples is about ten times higher than in the wet oxidized ones for equal initial thickness of the SiGe layer.

Co-decomposition of gaseous mixtures of silacyclopent-3-ene and Fe(CO)5 by irradiation at (9 + 10) and (9 + 10 + 5) µm from two CO2 lasers is reported. In a one-step process, this produced nanosized (α-Fe)-based particles that consist of both superparamagnetic and ferromagnetic phases. They were enveloped within a thin graphitic shell and embedded in an organosilicon polymer matrix. Properties of the nanocomposites, examined by infrared and Raman spectroscopies, high resolution transmission electron microscopy and magnetization studies, are shown to differ for the 2λ and 3λ irradiations. The latter consist of smaller Fe-based nanoparticles, display less graphitic carbon, possess more abundant Si/C/H phases and have their cores richer in Fe and superparamagnetic phase.

Erratum to ‘‘Tribological study of vanadium-based alloys ion implanted at low energy and high temperature’’ [Vacuum 67 (2002) 543–550] J.A. Garcia*, R. Rodriguez, R. Sanchez, R. Martinez, J.P. Riviere, P. Meheust, M. Varela, D. Caceres, A. Munoz, C. Ballesteros AIN-Centro de Ingenieria Avanzada de Superficies, C/San Cosme y San Damian s/n, Cordovilla, Pamplona 31191, Spain Laboratoire de Metallurgie Physique, UMR 6630 CNRS, Universite de Poitiers, Batiment SP2 MI, Boulevard Marie et Pierre Curie, B.P. 30179, F-86962 Futuroscope-Chasseneuil Cedex, France Universidad Carlos III, Dept. Fisica, Avda. Univerisdad 30, 28911 Leganes, Madrid, Spain

In the epitaxial growth of superlattice (SL) structures composed of non lattice-matched materials a large difference in the lattice constants of the components could result in the formation of misfit dislocations at the interfaces. However, high quality structures can be obtained when the thickness of the layers are kept below a critical value and the difference is elastically accomodated by strain. In particular GaAs-GaP short period superlattices (3.7% mismatch) constitute an interesting case of strained SLS because the stress related shifts of the electronic levels can result in novel optical and electronic properties. In the present work the quality of GaAs-GaP SLS is studied by STEM.Short period GaAs-GaP superlattices were grown on SI (001) GaAs substrates by Atomic Layer Molecular Beam Epitaxy a new modification of the MBE technique capable of a sharp modulation of both group III and group V sources. To study the possibility of using the GaAs-GaP system for SL and Quantum Well structures a 18 monolayer thick GaAs quantum well was confined by two GaAs-GaP superlattices.

The effect of annealing of the cathodoluminescence (CL) from deformed MgO single crystals has been investigated. Annealing at 1200 °C for a short time changes the bright slip bands into dark bands and also produces CL rosettes in indented crystals. The behaviour is attributed to annihilation and diffusion of point defects responsible for the CL emission. Es wird der Einflus der thermischen Behandlung auf die Kathodolumineszenz von verformten MgO-Einkristallen untersucht. Kurzes Anlassen bei 1200°C andert die Leuchtgleitbander in Dunkelgleitbander um und cryzeugt dunkle KL-Rosetten um Mikroharteeindrucke herum. Die Ergebnisse weisen darauf hin, das wahrend des Anlassens Vernichtung und Diffusion der Punktfehler, die KL erzeugen, stattfinden.

Undoped and Fe-doped MgAl2O4 spinel crystals have been studied using optical absorption and transmission electron microscopy. When thermochemically reduced at elevated temperatures, these crystals contained anion vacancies and exhibited a dark colouration that is attributed to Mie scattering from precipitates. Analytical electron-microscopy techniques reveal the presence of coherent metallic precipitates of Fe3Al. The precipitate distribution is inhomogeneous and their average size larger in the Fe-doped crystals.

Scanning electron microscopy (SEM), cathodoluminescence (CL), and optical absorption are used to investigate the effect of quenching on MgO single crystals. In order to separate the contribution of the plastic deformation, produced during quenching, the results are compared with those relative to deformed crystals. Mittels Rasterelektronemikroskopie, Kathodolumineszenz und optischer Absorption wird der Effekt des Abschreckens auf MgO-Einkristalle untersucht. Um den Beitrag der plastischen Ver-formung, die wahrend der Abschreckbehandlung stattfindet, vom totalen Effekt des Abschreckens zu trennen, wird ein Vergleich mit dem Effekt der Verformung durchgefuhrt.

Cathodoluminescence studies of hydrogen-doped MgO crystals thermochemically reduced at high temperatures show that there is no direct correlation between the intensity of the cathodoluminescence and photoluminescence bands. These crystals contain anion vacancies and H− ions. Luminescence bands at 2·95 eV (420 nm) and 2·4 eV (520 nm) correspond to emission from the two charge states of the anion vacancies. In contrast to photoluminescence, the intensity of the latter cathodoluminescence band is much smaller than that of the former. The effect of indentation and subsequent electron irradiation on the cathodoluminescence and photoluminescence is described.

MgO crystals doped with Co, Cu, and V were thermochemically reduced at high temperatures. Changes in coloration were observed in all these crystals due to broad optical extinction bands in the visible region. These bands are impurity related. Analytical transmission-electron-microscopy techniques indicated the presence of metallic precipitates consisting of Co in the Co-doped sample, Cu with some precipitates of Fe in the Cu-doped sample, and a V-Fe-Cr alloy in the V-doped sample. Microdiffraction patterns indicated that the Co precipitates possessed the fcc (a/sub 0/ = 3.54 A) crystal structure and V-Fe-Cr alloy precipitates showed a bcc (a/sub 0/ = 2.89 A) crystal structure.

The Cathodoluminescence (CL) emission from SrO single crystals, deformed under different mechanical treatments is studied in the scanning electron microscope. The CL spectrum depends on the kinds of deformation applied to the crystal. The main deformation-induced bands appear at 510 and 570 nm. The latter is markedly influenced by the state of the surface. Es wird die Katodolumineszenz von SrO-Einkristallen nach verschiedenen Verformungsproze-duren mittels Rasterelektronenmikroskopie untersucht. Das Katodolumineszenzspektrum hangt von der Art der Verformung ab. Die Verformung erzeugt Emissionsbanden bei 510 und 570 nm. Die 570 nm-Bande wird von dem Zustand der Oberflache beeinflust.

The effect of an electron beam on the cathodoluminescence from indented MgO single crystals has been studied in the scanning electron microscope. It has been found that the luminescence intensity and spectrum vary with irradiation time. The behavior is attributed to changes in impurities and vacancies defects.