In system photoelectron spectroscopy study of tin oxide layers produced from tetrakis dimethylamino tin by plasma enhanced atomic layer deposition

Tin oxide SnO2 layers were deposited using plasma enhanced atomic layer deposition with tetrakis dimethylamino tin precursor and oxygen plasma. The deposited layers were analyzed by spectral ellipsometry, conductivity measurements, and in system photoelectron spectroscopy. Within a deposition temperature range of 90 210 amp; 8201; C, the resistivity of the SnO2 layers decreases by 5 orders of magnitude with increasing deposition temperature. At the same time, the refractive index at 632.8 amp; 8201;nm increases from 1.7 to 1.9. These changes in bulk layer properties are connected to results from photoelectron spectroscopy. It is found that decreasing carbon and nitrogen contaminations in the tin oxide layers lead to decreasing optical band gaps and increasing refractive index. Additionally, for the deposited SnO2 layers, a shoulder in the O 1s core level spectrum is observed that decreases with the deposition temperature and thus is proposed to be related to hydroxyl group

Low Temperature Atomic Layer Deposited Magnesium Oxide as a Passivating Electron Contact for c Si Based Solar Cells

In this article, we explore magnesium oxide MgO as electron selective contact layer in silicon heterojunction solar cells. We report on the successful deposition of MgO layers by atomic layer deposition at low temperatures amp; 8804;200 C using bis ethylcyclopentadienyl magnesium Mg CpEt 2 and H2O as precursors. Depositions were carried out on bare crystalline silicon c Si wafers and c Si wafers with an intrinsic amorphous hydrogenated silicon i aSi H passivation layer. The resulting interfacial properties, surface passivation quality, and contact resistivity were investigated. Upon initial deposition of MgO on an i aSi H c Si stack, the c Si surface passivation degrades drastically. However, with an additional annealing step of 5 min at 200 250 C, it is possible to reverse the degradation and even to achieve charge carrier lifetimes in excess of those achieved with an i aSi H alone. Furthermore, we show that MgO forms an ohmic contact with both MgO i aSi H c Si and MgO c Si stacks, and we demonstrate solar cells using both types of stacks as electron contact layer

Stability and Dark Hysteresis Correlate in NiO-Based Perovskite Solar Cells

© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim In perovskite solar cells (PSCs), the interfaces are a weak link with respect to degradation. Electrochemical reactivity of the perovskite's halides has been reported for both molecular and polymeric hole selective layers (HSLs), and here it is shown that also NiO brings about this decomposition mechanism. Employing NiO as an HSL in p–i–n PSCs with power conversion efficiency (PCE) of 16.8%, noncapacitive hysteresis is found in the dark, which is attributable to the bias-induced degradation of perovskite/NiO interface. The possibility of electrochemically decoupling NiO from the perovskite via the introduction of a buffer layer is explored. Employing a hybrid magnesium-organic interlayer, the noncapacitive hysteresis is entirely suppressed and the device's electrical stability is improved. At the same time, the PCE is improved up to 18% thanks to reduced interfacial charge recombination, which enables more efficient hole collection resulting in higher Voc and FF

Endothelial function, regulation of angiogenesis and embryonic central hemodynamics in ART-conceived pregnancies

This study was undertaken to compare the concentrations of pro- and anti-angiogenic growth factors, nitric oxide (NO) stable metabolites in maternal serum and embryonic left ventricular (LV) isovolumic relaxation time (IRT, ms) during the first trimester in two groups of women: with pregnancy conceived by assisted reproductive technologies (ART, nј39) and normally conceived (control group, nј68) pregnancy. The concentration of vasoconstrictor endothelin 1 was 45.5 times more in ART than in control group. On the contrary, the concentrations of NO stable metabolites in ART were 1.9 times less than in control women. The assessment of angiogenic suppressors in ART women demonstrates the decrease in s-endoglin concentration was 1.6 times and in soluble receptor to vascular endothelial growth factor concentration was 2.0 times in comparison with control group. There was a significant increase in LV IRT in ART embryos in comparison to control ones. These data suggest significant changes in pro-antiangiogenic factors balance and increase in vascular impedance in ART-conceived embryos

Rapid scalable processing of tin oxide transport layers for perovskite solar cells

The development of scalable deposition methods for perovskite solar cell materials is critical to enable the commercialization of this nascent technology. Herein, we investigate the use and processing of nanoparticle SnO2 films as electron transport layers in perovskite solar cells and develop deposition methods for ultrasonic spray coating and slot-die coating, leading to photovoltaic device efficiencies over 19%. The effects of postprocessing treatments (thermal annealing, UV ozone, and O2 plasma) are then probed using structural and spectroscopic techniques to characterize the nature of the np-SnO2/perovskite interface. We show that a brief “hot air flow” method can be used to replace extended thermal annealing, confirming that this approach is compatible with high-throughput processing. Our results highlight the importance of interface management to minimize nonradiative losses and provide a deeper understanding of the processing requirements for large-area deposition of nanoparticle metal oxides

Nonspecific synaptic plasticity improves the recognition of sparse patterns degraded by local noise

Safaryan, K. et al. Nonspecific synaptic plasticity improves the recognition of sparse patterns degraded by local noise. Sci. Rep. 7, 46550; doi: 10.1038/srep46550 (2017). This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ © The Author(s) 2017.Many forms of synaptic plasticity require the local production of volatile or rapidly diffusing substances such as nitric oxide. The nonspecific plasticity these neuromodulators may induce at neighboring non-active synapses is thought to be detrimental for the specificity of memory storage. We show here that memory retrieval may benefit from this non-specific plasticity when the applied sparse binary input patterns are degraded by local noise. Simulations of a biophysically realistic model of a cerebellar Purkinje cell in a pattern recognition task show that, in the absence of noise, leakage of plasticity to adjacent synapses degrades the recognition of sparse static patterns. However, above a local noise level of 20 %, the model with nonspecific plasticity outperforms the standard, specific model. The gain in performance is greatest when the spatial distribution of noise in the input matches the range of diffusion-induced plasticity. Hence non-specific plasticity may offer a benefit in noisy environments or when the pressure to generalize is strong.Peer reviewe

Heterosynaptic plasticity in the neocortex

Ongoing learning continuously shapes the distribution of neurons’ synaptic weights in a system with plastic synapses. Plasticity may change the weights of synapses that were active during the induction—homosynaptic changes, but also may change synapses not active during the induction—heterosynaptic changes. Here we will argue, that heterosynaptic and homosynaptic plasticity are complementary processes, and that heterosynaptic plasticity might accompany homosynaptic plasticity induced by typical pairing protocols. Synapses are not uniform in their susceptibility for plastic changes, but have predispositions to undergo potentiation or depression, or not to change. Predisposition is one of the factors determining the direction and magnitude of homo- and heterosynaptic changes. Heterosynaptic changes which take place according to predispositions for plasticity may provide a useful mechanism(s) for homeostasis of neurons’ synaptic weights and extending the lifetime of memory traces during ongoing learning in neuronal networks

Search for Production of Invisible Final States in Single-Photon Decays of Υ(1S)Υ(1S)

We search for single-photon decays of the $Υ(1S)$ resonance, $Υ→γ+$ invisible, where the invisible state is either a particle of definite mass, such as a light Higgs boson $A^0$, or a pair of dark matter particles, $χ\overline{χ}$. Both $A^0$ and χ are assumed to have zero spin. We tag $Υ(1S)$ decays with a dipion transition $Υ(2S)→π^{+}π^{−}Υ(1S)$ and look for events with a single energetic photon and significant missing energy. We find no evidence for such processes in the mass range $m_{A^{0}}≤9.2 GeV$ and $m_{χ}≤4.5 GeV$ in the sample of $98×10^{6} Υ(2S)$ decays collected with the BABAR detector and set stringent limits on new physics models that contain light dark matter states.Physic

The Physics of the B Factories

This work is on the Physics of the B Factories. Part A of this book contains a brief description of the SLAC and KEK B Factories as well as their detectors, BaBar and Belle, and data taking related issues. Part B discusses tools and methods used by the experiments in order to obtain results. The results themselves can be found in Part C