Impact of MoS2 layer transfer on electrostatics of MoS2/SiO2 interface.

Using internal photoemission of electrons from few-monolayer thin MoS2 films into SiO2 we found that the MoS2 layer transfer processing perturbs electroneutrality of the interface, leading to an increase of the electron barrier height by ≈0.5-1 eV as compared to the case of the same films synthesized directly on SiO2. This effect is associated with the formation of an interface dipole, tentatively ascribed to interaction of H2O molecules with the SiO2 surface resulting in the incorporation of silanol (SiOH) groups. This violation of the interface electroneutrality may account for additional electron scattering in ultrathin transferred films and threshold voltage instabilities. Post-transfer annealing in H2S is shown to reduce the transfer-induced interface degradation.

A systematic study of various 2D materials in the light of defect formation and oxidation.

The thermodynamic aspects of various 2D materials are explored using Density Functional Theory (DFT). Various metal chalcogenides (MX2, M = metal, chalcogen X = S, Se, Te) are investigated with respect to their interaction and stability under different ambient conditions met in the integration process of a transistor device. Their interaction with high-κ dielectrics is also addressed, in order to assess their possible integration in Complementary Metal Oxide Semiconductor (CMOS) field effect transistors. 2D materials show promise for high performance nanoelectronic devices, but the presence of defects (vacancies, grain boundaries,…) can significantly impact their electronic properties. To assess the impact of defects, their enthalpies of formation and their signature levels in the density of states have been studied. We find, consistently with literature reports, that chalcogen vacancies are the most likely source of defects. It is shown that while pristine 2D materials are in general stable whenever set in contact with different ambient atmospheres, the presence of defective sites affects the electronic properties of the 2D materials to varying degrees. We observe that all the 2D materials studied in the present work show strong reactivity towards radical oxygen plasma treatments while reactivity towards other common gas phase chemical such as O2 and H2O and groups present at the high-κ surface varies significantly between species. While energy band-gaps, effective masses and contact resistivities are key criteria in selection of 2D materials for scaled CMOS and tunneling based devices, the phase and ambient stabilities might also play a very important role in the development of reliable nanoelectronic applications.

Paramagnetic Intrinsic Defects in Polycrystalline Large-Area 2D MoS2 Films Grown on SiO2 by Mo Sulfurization.

A low-temperature electron spin resonance study has been carried out on large-area high-purity polycrystalline two-dimensional few monolayer (ML) 2H MoS2 films synthesized by sulfurization of Mo layers, with intent to atomically assess mobility-degrading detrimental point defects. This reveals the presence of a distinct previously unreported anisotropic defect of axial symmetry about the c-axis characterized by g // = 2.00145 and g ⊥ = 2.0027, with corresponding density (spin S = ½) ~3 × 1012 cm-2 for a 4 ML thick film. Inverse correlation of the defect density with grain size points to a domain boundary associated defect, inherently incorporated during sample growth. Based on the analysis of ESR signal features in combination with literature data, the signal is tentatively ascribed to the a (di)sulfur antisite defect (S or S2 substituting for a Mo atom). Beset by these defects, the grain boundaries thus emerge as an intolerable threat for the carrier mobility and layer functionality.

Nucleation and growth mechanisms of Al2O3 atomic layerdeposition on synthetic polycrystalline MoS2.

Two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs) are of great interest for applications in nano-electronic devices. Their incorporation requires the deposition of nm-thin and continuous high-k dielectric layers on the 2D TMDs. Atomic layer deposition (ALD) of high-k dielectric layers is well established on Si surfaces: the importance of a high nucleation density for rapid layer closure is well known and the nucleation mechanisms have been thoroughly investigated. In contrast, the nucleation of ALD on 2D TMD surfaces is less well understood and a quantitative analysis of the deposition process is lacking. Therefore, in this work, we investigate the growth of Al2O3 (using Al(CH3)3/H2O ALD) on MoS2 whereby we attempt to provide a complete insight into the use of several complementary characterization techniques, including X-ray photo-electron spectroscopy, elastic recoil detection analysis, scanning electron microscopy, and time-of-flight secondary ion mass spectrometry. To reveal the inherent reactivity of MoS2, we exclude the impact of surface contamination from a transfer process by direct Al2O3 deposition on synthetic MoS2 layers obtained by a high temperature sulfurization process. It is shown that Al2O3 ALD on the MoS2 surface is strongly inhibited at temperatures between 125°C and 300°C, with no growth occurring on MoS2 crystal basal planes and selective nucleation only at line defects or grain boundaries at MoS2 top surface. During further deposition, the as-formed Al2O3 nano-ribbons grow in both vertical and lateral directions. Eventually, a continuous Al2O3 film is obtained by lateral growth over the MoS2 crystal basal plane, with the point of layer closure determined by the grain size at the MoS2 top surface and the lateral growth rate. The created Al2O3/MoS2 interface consists mainly of van der Waals interactions. The nucleation is improved by contributions of reversible adsorption on the MoS2 basal planes by using low deposition temperature in combination with short purge times. While this results in a more two-dimensional growth, additional H and C impurities are incorporated in the Al2O3 layers. To conclude, our growth study reveals that the inherent reactivity of the MoS2 basal plane for ALD is extremely low, and this confirms the need for functionalization methods of the TMD surface to enable ALD nucleation.

Differential signaling networks of Bcr-Abl p210 and p190 kinases in leukemia cells defined by functional proteomics.

The two major isoforms of the oncogenic Bcr-Abl tyrosine kinase, p210 and p190, are expressed upon the Philadelphia chromosome translocation. p210 is the hallmark of chronic myelogenous leukemia, whereas p190 occurs in the majority of B-cell acute lymphoblastic leukemia. Differences in protein interactions and activated signaling pathways that may be associated with the different diseases driven by p210 and p190 are unknown. We have performed a quantitative comparative proteomics study of p210 and p190. Strong differences in the interactome and tyrosine phosphoproteome were found and validated. Whereas the AP2 adaptor complex that regulates clathrin-mediated endocytosis interacts preferentially with p190, the phosphatase Sts1 is enriched with p210. Stronger activation of the Stat5 transcription factor and the Erk1/2 kinases is observed with p210, whereas Lyn kinase is activated by p190. Our findings provide a more coherent understanding of Bcr-Abl signaling, mechanisms of leukemic transformation, resulting disease pathobiology and responses to kinase inhibitors.

Nucleation and temperature-driven phase transitions of silicene superstructures on Ag(1 1 1).

Silicene grown on Ag(1 1 1) is characterized by several critical parameters. Among them, the substrate temperature plays a key role in determining the morphology during growth. However, an unexpected important role is also equally played by the post-deposition annealing temperature which determines the self-organization of silicene domains even in the submonolayer coverage regime and consecutive transitions between silicene with different periodicity. These temperature-driven phase transitions can be exploited to select the desired majority silicene phase, thus allowing for the manipulation of silicene properties.

Magnetism of TbPc2 SMMs on ferromagnetic electrodes used in organic spintronics.

Structural features and magnetic behaviour of TbPc2 thin films sublimated on LSMO and on cobalt surfaces have been investigated by synchrotron-based XNLD and XMCD techniques. Different orientation of the molecules is observed for the two substrates. No significant magnetic interaction with the ferromagnetic substrates is detected.

Self-organized broadband light trapping in thin film amorphous silicon solar cells.

Nanostructured glass substrates endowed with high aspect ratio one-dimensional corrugations are prepared by defocused ion beam erosion through a self-organized gold (Au) stencil mask. The shielding action of the stencil mask is amplified by co-deposition of gold atoms during ion bombardment. The resulting glass nanostructures enable broadband anti-reflection functionality and at the same time ensure a high efficiency for diffuse light scattering (Haze). It is demonstrated that the patterned glass substrates exhibit a better photon harvesting than the flat glass substrate in p-i-n type thin film a-Si:H solar cells.

Circular dichroism in the optical second-harmonic emission of curved gold metal nanowires.

Here we report the experimental observation of circular dichroism in the second-harmonic field (800-400 nm conversion) generated by self-organized gold nanowire arrays with subwavelength periodicity (160 nm). Such circular dichroism, raised by a nonlinear optical extrinsic chirality, is the evident signature of the sample morphology. It arises from the curvature of the self-assembled wires, producing a lack of symmetry at oblique incidence. The results were compared, both in the optical linear and nonlinear regime, with a reference sample composed of straight wires. Despite the weak extrinsic optical chirality of our samples (not observable by our optical linear measurements), high visibility (more than 50%) was obtained in the second-harmonic generated field.

The mouse SWISS-2D PAGE database: a tool for proteomics study of diabetes and obesity.

A number of two-dimensional electrophoresis (2-DE) reference maps from mouse samples have been established and could be accessed through the internet. An up-to-date list can be found in WORLD-2D PAGE (http://www.expasy.ch/ch2d/2d- index.html), an index of 2-DE databases and services. None of them were established from mouse white and brown adipose tissues, pancreatic islets, liver nuclei and skeletal muscle. This publication describes the mouse SWISS-2D PAGE database. Proteins present in samples of mouse (C57BI/6J) liver, liver nuclei, muscle, white and brown adipose tissue and pancreatic islets are assembled and described in an accessible uniform format. SWISS-2D PAGE can be accessed through the World Wide Web (WWW) network on the ExPASy molecular biology server (http://www.expasy.ch/ ch2d/).

Speech perception, lexicality, and reading skill.

This study examined the interaction between speech perception and lexical information among a group of 7-year-old children, of which 26 were poor readers and 36 were good readers. The children's performance was examined on tasks assessing reading skill, phonological awareness, pseudoword repetition, and phoneme identification. Although good readers showed clearly defined categorical perception in the phoneme identification task for both the /bif/-/pif/ and the /bis/-/pis/ continua, the category boundary for /bif/-/pif/ was at longer VOTs than the boundary for /bis/-/pis/, which characterizes the classic lexicality effect. Poor readers showed less sharply defined categorical perception on both continua. Although poor readers did not show the classic lexicality effect, lexicality did affect the overall rate with which phonemes were identified as /b/ or /p/ at each VOT. These findings suggest that the lexicon may operate as a compensatory mechanism for resolving ambiguities in speech perception. Furthermore, statistical correction for group differences in phoneme identification made group differences in phoneme deletion disappear, suggesting that deficits in speech perception may play a causal role in the phonological core deficit associated with reading failure.

The establishment of a human liver nuclei two-dimensional electrophoresis reference map.

This short communication describes the establishment of a two-dimensional electrophoresis (2-DE) reference map of nuclear proteins isolated from human liver. The human liver nuclei 2-DE reference map contains 1497 spots. In an initial identification study using peptide mass fingerprinting as a means of protein identification we were able to identify 26 spots corresponding to 15 different proteins. The human liver nuclei 2-DE reference map is now included in the SWISS-2DPAGE database, which can be accessed through the ExPASy server (http://www.expasy.ch/ch2d/).

Are metaphors elliptical similes?

What is the relation between metaphors and similes? Aristotle's "comparison theory" holds that metaphors are elliptical similes: "Sam is a pig" is simply a short form of "Sam is like a pig." In contrast, it has been suggested that metaphors cannot be elliptical similes because metaphors are "stronger" than similes. We know metaphors are stronger, it is argued, because of examples involving corrections, such as "Peter is not just like a rock, he is a rock." The argument from corrections can be challenged on logical and empirical grounds. The ability to correct a simile with a metaphor does not entail that metaphors are stronger than similes when used on their own, which is likely to be the most frequent case. Although four experiments indicate that when corrections are involved, metaphors are indeed stronger than similes in several respects, alas a further four experiments indicate that these differences are largely eliminated when metaphors and similes are used on their own. We note that this pattern of results is consistent with the comparison theory, and we offer an explanation of the effects of corrections.

Aptness predicts preference for metaphors or similes, as well as recall bias.

Why might we sometimes prefer a metaphor such as "genes are blueprints" to a simile such as "genes are like blueprints"? One possibility is that metaphors are preferred when the comparison between a tenor (e.g., genes) and a vehicle (e.g., blueprints) seems especially apt. That is, metaphors might be used when the comparison captures many salient features of the tenor in question. The present experiments examined the relation between the aptness of comparisons and people's preferences for expressing those comparisons as metaphors or as similes. In Experiment 1, it was found that there is consensus on how to express particular comparisons. In Experiment 2, it was found that this preference can be predicted from the aptness of a comparison. It was also found that aptness can predict errors in the recall of comparisons. These findings have implications for theories of metaphor.

Negative priming is not task bound: A consistent pattern across naming and categorization tasks.

When a word that was a to-be-ignored flanker on an initial prime trial becomes the target on the subsequent probe trial, responding to that word on the probe trial is slowed, a phenomenon callednegative priming. Virtually all prior studies have required subjects to perform the same task on both the prime and the probe trials. Thus, the extent to which negative priming is task bound is uncertain. We manipulated task factorially on the prime and probe trials, resulting in four groups: name-name, name-categorize, categorize-name, and categorize-categorize. The results showed equivalent negative priming of about 22 msec both within and between tasks for identical words, but no negative priming for semantically related words from the same category. These findings suggest (1) that negative priming for identical words can readily cross task types; and (2) that semantic negative priming does not occur for words, at least when categorical relatedness alone determines the semantic relation.