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In this paper, the atomic layer deposition (ALD) of ultra-thin films (80 ALD cycles, corresponding to 3.6 nm $Al_{2}O_{3}$ and 3.1 nm $HfO_{2}$. Current mapping by C-AFM showed, for the same applied bias, a uniform insulating behavior of $Al_{2}O_{3}$ and the occurrence of few localized breakdown spots in the case of $HfO_{2}$, associated to less compact films regions. Finally, an increase of the 1L-$MoS_{2}$ tensile strain was observed by Raman mapping after encapsulation with both high-k films, accompanied by a reduction in the PL intensity., 26 pages, 9 figures

The appearance of large, none-Gaussian cumulants of the baryon number distribution is commonly discussed as a signal for the QCD critical point. We review the status of the Taylor expansion of cumulant ratios of baryon number fluctuations along the freeze-out line and also compare QCD results with the corresponding proton number fluctuations as measured by the STAR Collaboration at RHIC. To further constrain the location of a possible QCD critical point we discuss poles of the baryon number fluctuations in the complex plane. Here we use not only the Taylor coefficients obtained at zero chemical potential but perform also calculations of Taylor expansion coefficients of the pressure at purely imaginary chemical potentials., Comment: 10 pages, 5 figures, talk presented at the Workshop "Criticality in QCD and the Hadron Resonance Gas", 29-31 July 2020, Online

We report on the first detection of very high-energy (VHE) gamma-ray emission from the Crab Nebula by a Cherenkov telescope in dual-mirror Schwarzschild-Couder (SC) configuration. The result has been achieved by means of the 4 m size ASTRI-Horn telescope, operated on Mt. Etna (Italy) and developed in the context of the Cherenkov Telescope Array Observatory preparatory phase. The dual-mirror SC design is aplanatic and characterized by a small plate scale, allowing us to implement large field of view cameras with small-size pixel sensors and a high compactness. The curved focal plane of the ASTRI camera is covered by silicon photo-multipliers (SiPMs), managed by an unconventional front-end electronics based on a customized peak-sensing detector mode. The system includes internal and external calibration systems, hardware and software for control and acquisition, and the complete data archiving and processing chain. The observations of the Crab Nebula were carried out in December 2018, during the telescope verification phase, for a total observation time (after data selection) of 24.4 h, equally divided into on- and off-axis source exposure. The camera system was still under commissioning and its functionality was not yet completely exploited. Furthermore, due to recent eruptions of the Etna Volcano, the mirror reflection efficiency was reduced. Nevertheless, the observations led to the detection of the source with a statistical significance of 5.4 sigma above an energy threshold of ~3 TeV. This result provides an important step towards the use of dual-mirror systems in Cherenkov gamma-ray astronomy. A pathfinder mini-array based on nine large field-of-view ASTRI-like telescopes is under implementation., 6 pages, 2 figures

The fct L10-FeNi alloy is a promising candidate for the development of high performance critical-elements-free magnetic materials. Among the different materials, the Au-Cu-Ni alloy has resulted very promising; however, a detailed investigation of the effect of the buffer-layer composition on the formation of the hard FeNi phase is still missing. To accelerate the search of the best Au-Cu-Ni composition, a combinatorial approach based on High-Throughput (HT) experimental methods has been exploited in this paper. HT magnetic characterization methods revealed the presence of a hard magnetic phase with an out-of-plane easy-axis, whose coercivity increases from 0.49 kOe up to 1.30 kOe as the Au content of the Cu-Au-Ni buffer-layer decreases. Similarly, the out-of-plane magneto-crystalline anisotropy energy density increases from 0.12 to 0.35 MJ/m3. This anisotropy is attributed to the partial formation of the L10 FeNi phase induced by the buffer-layer. In the range of compositions we investigated, the buffer-layer structure does not change significantly and the modulation of the magnetic properties with the Au content in the combinatorial layer is mainly related to the different nature and extent of interlayer diffusion processes, which have a great impact on the formation and order degree of the L10 FeNi phase.

We studied absorption, emission and lifetime of the coordination compound tris(2,2′-bipyridyl)ruthenium(II) fluorophore (Ru(bpy)32+) both dissolved in water solutions and dried. Lifetime measurements were carried out using a new detector, the Silicon Photomultiplier (SiPM), which is more sensitive and physically much smaller than conventional optical detectors, such as imager and scanner. Through these analyses and a morphological characterization with transmission electron microscopy, revealed its usability for sensor applications, in particular, as dye in optical DNA-chip technology, a viable alternative to the conventional CY5 fluorophore. The use of Ru(bpy)32+ would solve some of the typical disadvantages related to Cy5’s application, such as self-absorption of fluorescence and photobleaching. In addition, the Ru(bpy)32+ longer lifetime may play a key role in the definition of new optical DNA-chip. Keywords: Tris(2,2′-bipyridyl)ruthenium(II), Fluorophore, Spectroscopy, Lifetime measurements, SiPM, TEM

In this paper, the structural and electronic properties of epitaxial graphene (EG) grown on 8 degrees-off 4H-SiC (0001) by high temperature thermal processes have been extensively investigated by a combination of several high resolution characterization techniques. The increase in the number of graphene layers with the growth temperature (from 1600 to 1700 degrees C) was studied by microRaman spectroscopy and high resolution transmission electron microscopy (HRTEM) on cross sectioned samples. The few layers of graphene reside on a stepped SiC surface with alternating (0001) terraces and (11 - 2n) facets. Peculiar corrugations (wrinkles) in the graphene membrane preferentially oriented perpendicularly to the substrate steps were also observed. Motivated by recent atomic resolution studies of the EG/SiC interface revealing a local delamination of the interfacial C buffer from the (11 - 2n) facets, we searched for a correlation of these interfacial structural properties with the macroscopic electronic transport in EG field effect transistors (FETs). In particular, electrical characterization of EG Lop gated FETs fabricated with the channel length parallel or perpendicular to the substrate steps revealed a peculiar anisotropy of the channel conductance with respect to the steps orientation. This effect was explained in terms of a local enhancement of EG resistance on the (11-2n) facets with respect to the (0001) basal plane, which is consistent with a reduced doping due to the local buffer layer delamination from those facets. Furthermore, scanning probe microscopy-based local electron mean free path measurements on EG showed a similar to 3 x enhancement of mean free path On the buffer-layer-free (11-2n) facets with respect to (0001) terraces, probably associated to a strong reduction of Coulomb scattering effects on graphene's electrons. (C) 2013 Elsevier B.V. All rights reserved.

In this paper, the electronic transport in few layer graphene epitaxially grown on the Si face of 8 degrees off-axis 4H-SiC has been investigated using conductive atomic force microscopy (CAFM). The comparison between the two dimensional morphology and current maps in epitaxial graphene (EG) residing over the stepped SiC surface revealed a local resistance increase of EG over the (11 - 2n) facets with respect to the(0001) basal plane. This is consistent with a significant reduction of the carrier concentration, possibly approaching to the neutrality, in EG residing on facets with respect to the high n-type doping (similar to 10(13) cm(-2)) commonly found in EG on the basal plane. The observed difference can be ascribed to a different interfacestructure between EG and SiC on the two faces. The results of these nanoscale measurements allow us to explain the typically observed macroscopic anisotropy in EG conductivity with respect to the substrate steps orientation. (C) 2013 Elsevier B. V. All rights reserved.

Under the terms of the Creative Commons Attribution License 3.0 (CC-BY).-- et al., We report first-principles GW results on the dispersion of the bulk band-gap edges in the three-dimensional topological insulator Sb2Te3. We find that, independently of the reference density-functional-theory band structure and the crystal-lattice parameters used, the one-shot GW corrections enlarge the fundamental band gap, bringing its value in close agreement with experiment. We conclude that the GW corrections cause the displacement of the valence-band maximum (VBM) to the Γ point, ensuring that the surface-state Dirac point lies above the VBM. We extend our study to the analysis of the electron-energy-loss spectrum (EELS) of bulk Sb2Te3. In particular, we perform energy-filtered transmission electron microscopy and reflection EELS measurements. We show that the random-phase approximation with the GW quasiparticle energies and taking into account virtual excitations from the semicore states leads to good agreement with our experimental data., We acknowledge funding from the University of Basque Country UPV/EHU (IT-756-13), the Departamento de Educacion del Gobierno Vasco, the Tomsk State University Competitiveness Improvement Program, the Spanish Ministry of Economy and Competitiveness MINECO (Grant No. FIS2013-48286-C2-1-P), the Science Development Foundation under the President of the Republic of Azerbaijan [Grant No. EIF-2011-1(3)-82/69/4-M-50], and Saint Petersburg State University (Project No. 11.50.202.2015). The energy-filtered TEM experiment was performed at Beyond-Nano (PON a3-00363). The EELS experiment was performed at UNIMORE, and acknowledges partial support from PRIN GRAF 20105ZZTSE-008. The work was also supported by the Alexander von Humboldt Foundation through a postdoctoral fellowship, and by the Helmholtz Association through the Virtual Institute for Topological Insulators (VITI).

An innovative multilayer growth of InAs quantum dots on GaAs(100) is demonstrated to lead to self-aggregation of correlated quantum dot chains over mesoscopic distances. The fundamental idea is that at critical growth conditions is possible to drive the dot nucleation only at precise locations corresponding to the local minima of the Indium chemical potential. Differently from the known dot multilayers, where nucleation of new dots on top of the buried ones is driven by the surface strain originating from the dots below, here the spatial correlations and nucleation of additional dots are mostly dictated by a self-engineering of the surface occurring during the growth, close to the critical conditions for dot formation under the fixed oblique direction of the incoming As flux, that drives the In surface diffusion.

""In this paper we present a detailed study of the intersubband absorption occurring between electron states confined in strained Ge multi-quantum wells as a function of the temperature. The high structural quality of the samples is reflected by the very narrow absorption line-shape constant with temperature. We observe a temperature driven charge transfer occurring between the ground and the first excited subband which, in turn, induces a change in the depolarization shift and consequently in the energy of the absorbance peak. The experimental observations are well accounted for by a multi-valley k center dot p model.""

In this paper, silicon nanoparticles dispersed into a silica phase by sol–gel processing has been investigated by structural and nonlinear-optical characterization. The structural characterization has been performed by energy filtered and scanning transmission electron microscopy. A silicon nanoparticles mean radius of about 49 nm and a nanoparticle density of about 1.62 × 108 dots/cm2 have been obtained. Regarding nonlinear optics characterization, the observation of stimulated Raman scattering and the realization of a Raman amplifier based on silicon nanocomposites are described. Using a 1427 nm cw pump laser, amplification of Stokes signal, at 1542.2 nm, up to 1.4 dB/cm is demonstrated. A preliminary valuation of approximately a fivefold enhancement of the gain coefficient a significant reduction of threshold power are reported. Our findings have a potential interest for silicon-based Raman lasers.

Different physical and chemical methods can produce Si nanocomposite films, and most of them start with the deposition of silicon rich oxide (SRO) followed by hightemperature annealing [1].

Nowadays, the majority of the world’s most important oil and gas provinces have reached a mature stage. A proper exploitation and recovery maximisation primarily rely on the ability to foresee the consequences of different reservoir management decisions and production scenarios. Because of the inherent non-uniqueness of the history match process, using only one data-conditioned reservoir model to forecast hydrocarbon production may lead to erroneous interpretations and discrepancies with reality. A possible solution to this inverse problem and the related uncertainty quantification has been recently introduced by a novel methodology based on a stochastic search technique, called the Neighbourhood Algorithm (NA). The above methodology consists of two main steps: an optimization phase and an uncertainty assessment phase carried out in a Bayesian framework (NA-Bayes). After sampling acceptable data-fit regions of the parameter space, the posterior probabilities are calculated and a quantitative inference is performed. In this paper the NA-NAB approach was firstly evaluated by means of four analytical test functions (Branin, Six-Hump Camel Back, Goldstein and Price, Levy) with the aim of assessing its efficiency in searching and sampling the parameters space, verifying its stability and robustness and examining the effects of the algorithm control parameters. Two case studies are reported in order to investigate the suitability of the methodology for real fields. The hydrocarbon production, the pressure and the water cut were selected as match variables for the considered oil and gas reservoirs. The approach was promising and the results obtained were similar to those of the manually history matched model though achieved with a significant time reduction. In addition to the increased speed of history matching, the procedure allowed a proper uncertainty quantification by means of multiple production forecasts that better quantify risk and uncertainty in reservoir performance, which is crucial for economical evaluation and decision making.

Non volatile memories based on Si nanocrystals (Si-ncs) offer an important alternative to conventional floating gate devices, for the numerous potential advantages associated with the discrete-trap structures [1]. Isolated Si-ncs can be obtained by chemical vapor deposition (CVD) through a fully compatible CMOS process. So far, the main limitation for scaling the CVD Si-nc memories at sub-90 nm node is related to the expected fluctuation, from bit to bit, in the device threshold voltage (VTH), due to the spread in the sur- face fraction (Rdot) covered with Si dots [2]. The reason is the assumption that the dot position and the relative distance are fully random. It will be shown that the nucleation proc- ess is not purely random and the dot formation evolves with partial self-ordering. The relative dispersion of Rdot is nu- merically evaluated as a function of gate size, for random and partially self-ordered nucleation processes. The result is compared to data on VTH distribution and extrapolated to small gate areas.

We have studied the anatomic organization of corticopontine neurons in the monkey cytoarchitectonic areas 3a, 3b, 1, and 2. The purpose was to provide information about the composition of somatosensory cortical influence on cerebellar operations. Large tracer injections were made in the pontine nuclei. Retrogradely labeled neurons were confined to cortical layer 5, with the largest cell bodies located in area 3a and the smallest in area 3b. The distribution of labeled cells was quantitatively recorded and displayed in three-dimensional reconstructions and in flat maps. We have: (1) compared the average densities of labeled cells among the cytoarchitectonic areas, and (2) outlined the distribution of labeled cells within the cortical map of the body surface representation. The average density of labeled cells was considerably higher in areas 3a, 1, and 2, compared to area 3b. This finding suggests that areas 3a, 1, and 2 are more engaged in cerebellar operations than area 3b. We found marked density gradients of labeled cells within areas 3b, 1, and 2, but not within area 3a. When the density maps from areas 3b, 1, and 2 were superimposed on previously published somatotopic maps, we found higher average densities of corticopontine neurons in regions representing the trunk and proximal limbs, than in regions representing the distal forelimb. Thus, the distal forelimb representation, which is known to be strongly emphasized in terms of cortical volume, appears not to be correspondingly emphasized in the corticopontine projection.

Background While the haemodynamic benefits of DDDR pacing compared with DDD pacing in patients with brady– tachy syndrome and chronotropic incompetence (CI) are well demonstrated, the antiarrhythmic advantage is controversial and so far not clearly demonstrated. Aim We have performed a prospective, randomized, multicentre study to evaluate the efficacy of DDDR and DDD pacing modes in preventing paroxysmal atrial fibrillation (PAF) episodes in patients with brady–tachy syndrome and CI. Methods and Results Seventy-eight patients were included in the study. All patients had a dual chamber pacemaker implanted and were randomly programmed to DDD or DDDR with a cross over (DDD DDDR or vice versa) at 3 months. The final evaluation was performed at 6 months by means of two self-administered symptom questionnaires to evaluate activity. Symptoms of palpitations were analysed and scored. The patients were less symptomatic with the DDDR mode. The number of modeswitch activations compared with symptomatic episodes of PAF confirmed the high rate of asymptomatic PAF episodes in patients with brady–tachy syndrome. We conclude that in a small but well defined population of patients affected by sick sinus syndrome with CI and severely symptomatic PAF, DDDR pacing compared with DDD pacing may offer an additional antiarrhythmic benefit and should be considered the primary mode of pacing. (Europace 1999; 1: 220–225)

Idiopathic left ventricular aneurysm (LVA) is a very rare clinical condition. This article describes a patient with idiopathic LVA associated with episodes of ventricular tachycardia and ventricular fibrillation. Clinical and instrumental examinations did not reveal the pathogenesis of the aneurysm. The malignant clinical course suggests that an aggressive antiarrhythmic treatment, including ICD implantation, may be warranted.

Introduction Vascular endothelial growth factor (VEGF) is an endothelial cell mitogen. The objective of this study was to verify the proregenerative effects of VEGF in an experimental model of acute liver failure. Materials and methods Sixty four rats that underwent intraperitoneal injection of carbon tetrachloride (CCl 4 ) were randomly divided into two groups: group B animals received intravenous injection of VEGF 164 1 hour following CCl 4 poisoning. Group A hosts were untreated. To obtain daily liver function tests (LFTs) and histological samples, on each day up to 8 days we sacrificed four rats in each group. Results The laboratory examinations showed notable alteration of LFTs in group A, while group B revealed only slight changes. The histological examination showed greater liver damage in group A compared with group B. Conclusion Our results suggest that administration of exogenous VEGF protects the liver from CCl 4 -induced acute hepatic failure. Further studies are underway to assess whether exogenous VEGF is effective in other liver injuries.

On the basis of recent results, concerning the quantitative determination of the clustered silicon concentration in substoichiometric silicon oxide layer and based on electron energy loss spectroscopy (EELS) and energy-filtered transmission electron microscopy, in this paper we demonstrate that the structural properties of Si nanoclusters (Si ncs) strongly depend on the technique used for specimen preparation. In particular here we report on annealed SiOx films prepared by plasma enhanced chemical vapour deposition (PECVD) and magnetron sputtering, showing that their structural properties are very different. It is shown that in PECVD films only around 30% of the Si excess agglomerates in clusters while an almost complete agglomeration occurs in sputtered films. These data are explained on the basis of the different initial structural properties of the as-deposited films which become crucial for the subsequent evolution.

Previous investigations have shown that the transplant of fetal nervous tissue in adult, formerly injured, brain induces an improvement of the neurological deficits. The process underlying this finding is not yet known. It has been proposed that this process is favourably supported by the reconstruction of the damaged circuitry, replacing the injured neurons with the transplanted fetal cells. In the present study we have investigated the relation between the improvement of the neurological deficits and the anatomical integration of the transplanted neurons within the host brain. The plan of the investigation included two steps: the first step consisted of inducing neurological deficits by kainic acid lesion of the motor cortex and then studying the changes in the motor learning following a homotopic transplant of fetal cortex in the side of the lesion. The second step consisted of studying the anatomical integration of the transplanted cortex with the thalamus of the host. The results showed that the rats with injury of the motor cortex followed by solid transplant of fetal cortex (E 17) had a significantly greater recovery of the motor learning with respect to non-transplanted rats with a lesioned motor cortex. In the same rats, the connections between the transplanted cerebral cortex and the thalamus of the host has been investigated. WGA-HRP solution was injected in the thalamus and both labeled fiber terminals and labeled cells were searched for in the transplants. The results showed that: 1) the host thalamus projects to the transplanted cortex with a lower density than to the host cortex surrounding the transplant; 2) the thalamic projection to the host cortex is topographically organized, whereas the projection to the transplant is arranged in patches without any topographical organization; 3) the transplant does not send a significant projection to the thalamus of the host. In conclusion, the experimental findings demonstrate that the reconstruction of an injured thalamo-cortical circuitry of adult rats transplanting fetal neurons is not possible. The improvement of the functional deficits by the transplant of fetal tissue may be referred to aspecific factors enhancing the functional activity of the host cortex undamaged by the initial injury. The identification of the nature of the hypothesized factors requires further investigation.

The motor organization of the nucleus lateralis (NL) of the cerebellum of the rat was investigated by studying the motor effects following the electrical microstimulation. The movements evoked by the NL stimulation concerned prevalently the forelimb and the head segments. The movements of the hindlimb segments were evoked in only few cases. The NL is organized as a mosaic of zones without, or at least very little overlap. The various body segments are differently represented in the NL. Some of them are once represented (single representations). In other cases, the same movements were evoked by different NL regions (multiple representations). Finally, in a last lot of cases, various representations concerned the same body regions but from each representation a different type of movement was evoked (specific representations, i.e. displacement of an individual digit and flexion of all digits together). The topographical distribution of the representations in the NL cytological regions (magnicellularis, NLm; dorsolateral hump, DLH; subnucleus lateralis parvocellularis, slp) suggests the idea that each of them may be concerned in a specific motor activity: the NLm would control the position of the body, or of part of it, in the space; the DLH would be concerned in the oral (prevalently) and in the forelimb motor activity; the slp would be concerned in the exploration of the environment as well as in skilled movements of the distalmost forelimb segments.

The present research was planned to study the possibility to reconstruct a damaged neural circuitry by replacing the injured neurons with homotopic fetal cells. In adult rats the motor cortex was injured with intracortical injection of kainic acid solution. After a delay of 10-14 days, a block of cerebral cortex of fetal rats (E17) was transplanted in the cavity produced by the kainic acid in the motor cortex. After 2-3 months, WGA-HRP solution was injected in the thalamus of the host and both anterogradely labeled fiber terminals and retrogradely labeled somata cells were researched in the transplanted cortex. The results showed that: 1) the host thalamus projects to the transplanted cortex with less density compared to the host cortex surrounding the transplant; 2) the thalamic projection to the transplant is not topographically organized whereas the projection to the host cortex is; 3) the transplant was virtually void of a significant projection to the thalamus of the host. In conclusion, the results offer direct evidence that the reconstruction of an injured thalamocortical circuitry of adult rat is not possible by transplanting homotopic fetal neurons.

Holographic measurements to determine deviations of the 32m Noto antenna with respect to an ideal parabolic surface have been performed at 11.5 GHz. An 'ad hoc' system including a reference secondary antenna was built, and digital beacons coming from commercial TV satellites were used as signal sources. Results clearly showed significant deformations of the dish.

(1986). Hydrobiology and Fish biology. Bollettino di zoologia: Vol. 53, No. sup001, pp. 93-100.

HeI and HeII photoelectron spectra (UPS) of the following compounds are reported and discussed: R 3 Sn(S 2 CNR′ 2 ) (R,R′  CH 3 , C 2 H 5 ) (trialkyltin N,N -dialkyldithiocarbamates), R 2 Sn(S 2 CNR′ 2 ) 2 (R  CH 3 , n-C 4 H 9 , R  CH 3 ) (dialkyltin bis- N,N -dimethyldithiocarbamates), R 2 PS 2 R (R  C 2 H 5 ) (ethyldiethyldithiophosphinate), R 3 Sn(S 2 PR′ 2 ) (R, R′ CH 3 ) (trimethyltin dimethyldithiophosphinate), R 2 Sn(S 2 PR′ 2 ) 2 (R  CH 3 , n-C 4 H 9 , R′  C 2 H 5 ) (dialkyltin bis-diethyldithiophosphinates). The assignments are made by comparison with UP spectra of related molecules and the results of CNDO/2 calculations. A scheme for the energy levels of the valence shells is proposed.

We present a calculation of the net baryon number density as a function of imaginary baryon number chemical potential, obtained with highly improved staggered quarks (HISQ) at temporal lattice extent of $N_\tau=4,6$. We construct various rational function approximations of the lattice data and discuss how poles in the complex plane can be determined from them. We compare our results of the singularities in the chemical potential plane to the theoretically expected positions of the Lee-Yang edge singularity in the vicinity of the Roberge-Weiss and chiral phase transitions. We find a temperature scaling that is in accordance with the expected power law behavior., Comment: 22 pages, 22 figures, published version

The Square Kilometer Array (SKA) project aims at building the world’s largest radio observatory to observe the sky with unprecedented sensitivity and collecting area. In the first phase of the project (SKA1), an array of dishes, SKA1-MID, will be built in South Africa. It will consist of 133 15m-dishes, which will include the MeerKAT array, for the 0.350-20 GHz frequency band observations. Each antenna will be provided with a local monitor and control system (LMC), enabling operations both to the Telescope Manager remote system, and to the engineers and maintenance staff; it provides different environment for the telescope control (positioning, pointing, observational bands), metadata collection for monitoring and database storaging, operational modes and functional states management for all the telescope capabilities. In this paper we present the LMC software architecture designed for the detailed design phase (DD), where we describe functional and physical interfaces with monitored and controlled sub-elements, and highlight the data flow between each LMC modules and its sub-element controllers from one side, and Telescope Manager on the other side. We also describe the complete Product Breakdown Structure (PBS) created in order to optimize resources allocation in terms of calculus and memory, able to perform required task for each element according to the proper requirements. Among them, time response and system reliability are the most important, considering the complexity of SKA dish network and its isolated placement. Performances obtained by software implementation using TANGO framework will be discussed, matching them with technical requirements derived by SKA science drivers.

The synthesis of photoluminescent nanomaterials based on halloysite nanotubes is described. The obtained hybrid was characterized by means of TGA, FT-IR, DLS and XPS measurements; in addition its morphology was imaged by TEM and HR-TEM. The HNT hybrid also exhibited photoluminescent properties, both in solution and in the solid state, and white-light emission (0.24, 0.36; CIE coordinates) was observed. This work could be pioneering as a new strategy for manufacturing both LEDs and fluorescent tags based on HNT nanomaterials. © 2018 The Royal Society of Chemistry.

We have used Raman spectroscopy, transmission electron microscopy, x-ray diffraction, and x-ray photoemission spectroscopy to investigate strain relaxation mechanism of Si(0.22)Ge(0.78) heteroepitaxial layer deposited on Si substrates in tensile, neutral, and compressive strain conditions. The three regimes have been obtained by interposing between the SiGe layer and the substrate a fully relaxed Ge layer, a partially relaxed Ge layer, or growing directly the alloy on Si. We found that the deposition of a Ge buffer layer prior to the growth of the SiGe is very promising in view of the realization of thin virtual substrates on silicon to be used for the deposition of strain-controlled high Ge content SiGe alloys. We demonstrate that this is mainly due to the strain relaxation mechanism in the Ge layer occurring via insertion of pure edge 90 degrees misfit dislocations (MDs) and to the confinement of threading arms in to the Ge layer due to a second MD network formed at the SiGe/Ge heterointerface.

Research on band-gap engineering of Silicon-Germanium heterostructures for the realization of Quantum Cascade (QC) structures emitting in the Terahertz (THz) spectral region has recently attracted a vast interest. While several successful attempts have been reported using hole-based (p-type) intersubband transitions, very few results have been published on systems exploiting electrons (n-type). In this work we present the optical and structural characterization of n-type heterostructures made either of tensely-strained Si (sSi) quantum well (QW) confined between low Ge content Si1-xGex barriers [0.2