Effect of gallium termination on InGaAs wetting layer properties in droplet epitaxy InGaAs quantum dots

Self-assembled quantum dots based on III-V semiconductors have excellent properties for applications in quantum optics. However, the presence of a 2D wetting layer which forms during the Stranski-Krastanov growth of quantum dots can limit their performance. Here, we investigate wetting layer formation during quantum dot growth by the alternative droplet epitaxy technique. We use a combination of photoluminescence excitation spectroscopy, lifetime measurements, and transmission electron microscopy to identify the presence of an InGaAs wetting layer in these droplet epitaxy quantum dots, even in the absence of distinguishable wetting layer photoluminescence. We observe that increasing the amount of Ga deposited on a GaAs (100) surface prior to the growth of InGaAs quantum dots leads to a significant reduction in the emission wavelength of the wetting layer to the point where it can no longer be distinguished from the GaAs acceptor peak emission in photoluminescence measurements

In-plane magnetic field-driven symmetry breaking in topological insulator-based three-terminal junctions

Topological surface states of three-dimensional topological insulator nanoribbons and their distinct magnetoconductance properties are promising for topoelectronic applications and topological quantum computation. A crucial building block for nanoribbon-based circuits are three-terminal junctions. While the transport of topological surface states on a planar boundary is not directly affected by an in-plane magnetic field, the orbital effect cannot be neglected when the surface states are confined to the boundary of a nanoribbon geometry. Here, we report on the magnetotransport properties of such three-terminal junctions. We observe a dependence of the current on the in-plane magnetic field, with a distinct steering pattern of the surface state current towards a preferred output terminal for different magnetic field orientations. We demonstrate that this steering effect originates from the orbital effect, trapping the phase-coherent surface states in the different legs of the junction on opposite sides of the nanoribbon and breaking the left-right symmetry of the transmission across the junction. The reported magnetotransport properties demonstrate that an in-plane magnetic field is not only relevant but also very useful for the characterization and manipulation of transport in three-dimensional topological insulator nanoribbon-based junctions and circuits, acting as a topoelectric current switch.Comment: Main Text (8 pages, 5 figures) + Supplemental Material (13 pages, 10 figures

Níveis de lisina digestível em rações, em que se manteve ou não a relação aminoacídica, para frangos de corte de 1 a 21 dias de idade, mantidos em estresse por calor

Dois ensaios foram conduzidos para avaliar os efeitos de níveis de lisina digestível em rações em que se manteve ou não a relação aminoacídica sobre o desempenho de frangos de corte machos de 1 a 21 dias de idade, criados em alta temperatura. O delineamento experimental utilizado em ambos os ensaios foi o inteiramente casualizado. As aves, no ensaio 1, foram distribuídas em cinco tratamentos (0,92; 0,98; 1,04; 1,10 e 1,16% de lisina digestível em ração convencional), oito repetições e dez aves por repetição. No ensaio 2, os frangos foram distribuídos em quatro tratamentos (1,04; 1,10; 1,16 e 1,22% de lisina digestível em rações mantendo a relação aminoacídica), oito repetições e dez aves por repetição. No ensaio 1, os tratamentos influenciaram quadraticamente o ganho de peso e o consumo de ração, que aumentaram até os níveis de 1,14 e 1,09% de lisina, respectivamente. Embora a conversão alimentar tenha melhorado de forma linear, o modelo LRP foi o que melhor se ajustou aos dados, estimando em 1,097% o nível de lisina a partir do qual ocorreu um platô. Não houve efeito dos tratamentos sobre os pesos absolutos do coração, fígado e intestinos, enquanto o peso absoluto da moela aumentou linearmente. O peso absoluto da carcaça aumentou, enquanto os pesos relativos do coração e do fígado reduziram quadraticamente com os tratamentos. No ensaio 2, os tratamentos influenciaram de forma linear crescente o ganho de peso e a conversão alimentar, enquanto o consumo de ração não variou. Os tratamentos influenciaram linearmente o peso absoluto da carcaça, enquanto os pesos absoluto e relativo das vísceras não variaram. Concluiu-se que frangos de corte machos, de 1 a 21 dias de idade, mantidos em estresse por calor, exigem, no mínimo, 1,14 e 1,22% de lisina digestível em ração convencional e em ração em que se manteve a relação aminoacídica, respectivamente.Two trials were conducted to evaluate the effects of digestible lysine levels in diets maintaining or not the relationship of amino acids, on performance of broilers from 1 to 21 days, kept under heat stress. A completely randomized experimental design was used in both trials. In the trial 1, the broilers were allotted in five treatments (0.92; 0.98; 1.04; 1.10 and 1.16% of lysine in conventional diets), eight replicates and ten broilers per replicate. In the trial 2, the broilers were allotted in four treatments (1.04; 1.10; 1.16 and 1.22% of lysine in diet maintaining the relationship of amino acids), eight replicates and ten broilers per replicate. In the trial 1, the digestible lysine levels influenced quadraticly the weight gain and the feed intake that increased up to 1.14 and 1.09%, respectively. Although feed:gain ratio had changed by linear way, the LRP model adjusted better to the data, estimating in 1.097% the lysine level where occurred a "plateau". There was no effect of treatments on absolute weights of heart, liver and intestines, while the absolute weight of gizzard increased linearly. The absolute weight of carcass increased while the relative weights of heart and liver reduced quadraticly. In the trial 2, the treatments influenced in a crescent linear way the weight gain and the feed:gain ratio while the feed intake was not influenced. The treatments influenced linearly the absolute weight of carcass while the absolute and relative weights of the organs were not influenced. It was concluded that male broilers, in the period from 1 to 21 days of age, kept under heat stress, require at least 1.14 and 1.22% of digestible lysine in conventional diet and in diet maintaining the relationship of amino acid, respectively

Filtered EBSD data set of listvenites from Oman Drilling Project Hole BT1B

The dataset contains electron backscattered diffraction (EBSD) filtered data acquired on samples collected on cores from Oman Drilling Project Hole BT1B (International Continental Drilling Project Expedition 5057‐4B). A suite of 7 samples in foliated listvenites was analyzed through 11 EBSD maps of variable area width at specific sites of interest. The scanning resolution varies from 0.5 µm to 3 µm. Raw pixel data was filtered with the Channel 5 analysis suite from HKL Technology (Oxford Instruments) and consists in noise reduction followed by a wild spikes extrapolation (level 6; in few cases level 5). Datafiles are provided as channel text files (CTF), which can be processed and viewed with Channel 5 or MTEX

Ductile deformation during carbonation of serpentinized peridotite

Carbonated serpentinites (listvenites) in the Samail Ophiolite, Oman, record mineralization of 1–2 Gt of CO2, but the mechanisms providing permeability for continued reactive fluid flow are unclear. Based on samples of the Oman Drilling Project, here we show that listvenites with a penetrative foliation have abundant microstructures indicating that the carbonation reaction occurred during deformation. Folded magnesite veins mark the onset of carbonation, followed by deformation during carbonate growth. Undeformed magnesite and quartz overgrowths indicate that deformation stopped before the reaction was completed. We propose deformation by dilatant granular flow and dissolution-precipitation assisted the reaction, while deformation in turn was localized in the weak reacting mass. Lithostatic pore pressures promoted this process, creating dilatant porosity for CO2 transport and solid volume increase. This feedback mechanism may be common in serpentinite-bearing fault zones and the mantle wedge overlying subduction zones, allowing massive carbonation of mantle rocks

A Novel Gate-Normal Tunneling Field-Effect Transistor With Dual-Metal Gate

In this combined experiment and simulation study we investigate a SiGe/Si based gatenormal tunneling field-effect transistor (TFET) with a pillar shaped contact to the tunneling junction which brings forth two significant advantages. The first, is improved electrostatics at the boundary of the tunneling junction which helps to diminish the influence of adverse tunneling paths, and thus, substantially sharpens the device turn on. The second, is a simplified fabrication of a dual-metal gate using a selfaligned process. We demonstrate the feasibility of the process and show the positive effect of a dual-metal gate in experiment. Overall the paper provides general guidelines for the improvement of the subthreshold swing in gate-normal TFETs which are not restrained to the material system

Phase Stability of Nanolaminated Epitaxial (Cr1–xFex)2AlC MAX Phase Thin Films on MgO(111) and Al2O3 (0001) for Use as Conductive Coatings

In this study, we model the chemical stability in the (Cr1–xFex)2AlC MAX phase system using density functional theory, predicting its phase stability for 0 < x < 0.2. Following the calculations, we have successfully synthesized nanolaminated (Cr1–xFex)2AlC MAX phase thin films with target Fe contents of x = 0.1 and x = 0.2 by pulsed laser deposition using elemental targets on MgO(111) and Al2O3(0001) substrates at 600 °C. Structural investigations by X-ray diffraction and transmission electron microscopy reveal MAX phase epitaxial films on both substrates with a coexisting (Fe,Cr)5Al8 intermetallic secondary phase. Experiments suggest an actual maximum Fe solubility of 3.4 at %, corresponding to (Cr0.932Fe0.068)2AlC, which is the highest Fe doping level achieved so far in volume materials and thin films. Residual Fe is continuously distributed in the (Fe,Cr)5Al8 intermetallic secondary phase. The incorporation of Fe results in the slight reduction of the c lattice parameter, while the a lattice parameter remains unchanged. The nanolaminated (Cr0.932Fe0.068)2AlC thin films show a metallic behavior and can serve as promising candidates for highly conductive coatings

Optical and structural characterization of orthorhombic LaLuO3 using extreme ultraviolet reflectometry

A thin orthorhombic LaLuO3 film, grown on SrTiO3 substrate by pulsed laser deposition, is characterized using multi-angle spectral extreme ultraviolet reflectometry (EUVR). Layer structure parameters and optical constants of LaLuO3 are determined simultaneously by fitting angular reflectivity curves in a wide spectral range (70–200 eV). From near-edge optical constant analysis, La:Lu stoichiometry ratio and the film density are derived. Sample structure is additionally analyzed using XRR, AFM and TEM methods. EUVR as a method of structural characterization is discussed in comparison with XRR. Correlation error analysis of the layer structure parameters, obtained from independent EUVR and XRR fits, is presented

Signatures of induced superconductivity in AlOx-capped topological heterostructures

In order to access exotic Dirac and Majorana states in (Bi,Sb)-based topological insulators (TIs), the physical surface of those crystals should not be exposed to air. 2–3 nm of in situ deposited Al on top of pristine TI thin films immediately oxidizes after taking the sample to ambient conditions. The native AlOx provides a favorable hard capping, which preserves the topological surface states during ex situ device fabrication. Here, we present a process on how to construct superconductor – topological insulator – superconductor (S-TI-S) junctions from in situ capped thin films comprised of 15 nm Sb2Te3 on top of 6 nm Bi2Te3. The thicknesses of the Sb2Te3 and the Bi2Te3 layer allow us to precisely tune the Fermi level of the upper surface of the Sb2Te3 layer. The challenge is to provide a transparent interface between Sb2Te3 and the superconductive Nb, while assuring an AlOx-capped weak link in between two closely separated Nb electrodes. Low temperature experiments on our junctions provide evidence for charge transport mediated by coherent Andreev states. Magnetic field dependent measurements yielded Fraunhofer-like patterns, whose periodicities are in good agreement with the effective areas of the respective junctions. Transmission electron micrographs of the narrowest junction confirm a crystalline and capped weak link. Our results provide the first reported signatures of induced superconductivity in S-TI-S junctions, which are capped by native AlOx. The presented process allows for accessing S-TI hybrid devices via magnetic flux, while assuring in situ conserved weak links. This makes as-prepared junctions a promising platform for proposed flux-controllable Majorana devices