High-Throughput Micro-Combinatorial TEM Phase Mapping of the DC Magnetron Sputtered YxTi1-xOy Thin Layer System.

High-throughput methods are extremely important in today's materials science, especially in the case of thin film characterization. The micro-combinatorial method enables the deposition and characterization of entire multicomponent thin film systems within a single sample. In this paper, we report the application of this method for the comprehensive TEM characterization of the Y-Ti-O layer system. Variable composition samples (YxTi1-xOy) were prepared by dual DC magnetron sputtering, covering the entire (0 ≤ x ≤ 1) concentration range. The structure and morphology of phases formed in both as-deposited and annealed samples at 600, 700, and 800 °C were revealed as a function of Y-Ti composition (x). A comprehensive map showing the appropriate amorphous and crystalline phases, and their occurrence regions of the whole Y-Ti-O layer system, was revealed. Thanks to the applied method, it was shown with ease that at the given experimental conditions, the Y2Ti2O7 phase with a pyrochlore structure forms already at 700 °C without the TiO2 and Y2O3 by-phases, which is remarkably lower than the required temperature for most physical preparation methods, demonstrating the importance and benefits of creating phase maps in materials science and technology.

Interface Properties of MoS2 van der Waals Heterojunctions with GaN.

The combination of the unique physical properties of molybdenum disulfide (MoS2) with those of gallium nitride (GaN) and related group-III nitride semiconductors have recently attracted increasing scientific interest for the realization of innovative electronic and optoelectronic devices. A deep understanding of MoS2/GaN interface properties represents the key to properly tailor the electronic and optical behavior of devices based on this heterostructure. In this study, monolayer (1L) MoS2 was grown on GaN-on-sapphire substrates by chemical vapor deposition (CVD) at 700 °C. The structural, chemical, vibrational, and light emission properties of the MoS2/GaN heterostructure were investigated in detail by the combination of microscopic/spectroscopic techniques and ab initio calculations. XPS analyses on as-grown samples showed the formation of stoichiometric MoS2. According to micro-Raman spectroscopy, monolayer MoS2 domains on GaN exhibit an average n-type doping of (0.11 ± 0.12) × 1013 cm-2 and a small tensile strain (ε ≈ 0.25%), whereas an intense light emission at 1.87 eV was revealed by PL analyses. Furthermore, a gap at the interface was shown by cross-sectional TEM analysis, confirming the van der Waals (vdW) bond between MoS2 and GaN. Finally, density functional theory (DFT) calculations of the heterostructure were carried out, considering three different configurations of the interface, i.e., (i) an ideal Ga-terminated GaN surface, (ii) the passivation of Ga surface by a monolayer of oxygen (O), and (iii) the presence of an ultrathin Ga2O3 layer. This latter model predicts the formation of a vdW interface and a strong n-type doping of MoS2, in closer agreement with the experimental observations.

Photocatalytic H2 Production by Visible Light on Cd0.5Zn0.5S Photocatalysts Modified with Ni(OH)2 by Impregnation Method.

Nowadays, the study of environmentally friendly ways of producing hydrogen as a green energy source is an increasingly important challenge. One of these potential processes is the heterogeneous photocatalytic splitting of water or other hydrogen sources such as H2S or its alkaline solution. The most common catalysts used for H2 production from Na2S solution are the CdS-ZnS type catalysts, whose efficiency can be further enhanced by Ni-modification. In this work, the surface of Cd0.5Zn0.5S composite was modified with Ni(II) compound for photocatalytic H2 generation. Besides two conventional methods, impregnation was also applied, which is a simple but unconventional modification technique for the CdS-type catalysts. Among the catalysts modified with 1% Ni(II), the impregnation method resulted in the highest activity, for which a quantum efficiency of 15.8% was achieved by using a 415 nm LED and Na2S-Na2SO3 sacrificial solution. This corresponded to an outstanding rate of 170 mmol H2/h/g under the given experimental conditions. The catalysts were characterized by DRS, XRD, TEM, STEM-EDS, and XPS analyses, which confirmed that Ni(II) is mainly present as Ni(OH)2 on the surface of the CdS-ZnS composite. The observations from the illumination experiments indicated that Ni(OH)2 was oxidized during the reaction, and that it therefore played a hole-trapping role.

The composition and structure of the ubiquitous hydrocarbon contamination on van der Waals materials.

The behavior of single layer van der Waals (vdW) materials is profoundly influenced by the immediate atomic environment at their surface, a prime example being the myriad of emergent properties in artificial heterostructures. Equally significant are adsorbates deposited onto their surface from ambient. While vdW interfaces are well understood, our knowledge regarding atmospheric contamination is severely limited. Here we show that the common ambient contamination on the surface of: graphene, graphite, hBN and MoS2 is composed of a self-organized molecular layer, which forms during a few days of ambient exposure. Using low-temperature STM measurements we image the atomic structure of this adlayer and in combination with infrared spectroscopy identify the contaminant molecules as normal alkanes with lengths of 20-26 carbon atoms. Through its ability to self-organize, the alkane layer displaces the manifold other airborne contaminant species, capping the surface of vdW materials and possibly dominating their interaction with the environment.

Multiscale Investigation of the Structural, Electrical and Photoluminescence Properties of MoS2 Obtained by MoO3 Sulfurization.

In this paper, we report a multiscale investigation of the compositional, morphological, structural, electrical, and optical emission properties of 2H-MoS2 obtained by sulfurization at 800 °C of very thin MoO3 films (with thickness ranging from ~2.8 nm to ~4.2 nm) on a SiO2/Si substrate. XPS analyses confirmed that the sulfurization was very effective in the reduction of the oxide to MoS2, with only a small percentage of residual MoO3 present in the final film. High-resolution TEM/STEM analyses revealed the formation of few (i.e., 2-3 layers) of MoS2 nearly aligned with the SiO2 surface in the case of the thinnest (~2.8 nm) MoO3 film, whereas multilayers of MoS2 partially standing up with respect to the substrate were observed for the ~4.2 nm one. Such different configurations indicate the prevalence of different mechanisms (i.e., vapour-solid surface reaction or S diffusion within the film) as a function of the thickness. The uniform thickness distribution of the few-layer and multilayer MoS2 was confirmed by Raman mapping. Furthermore, the correlative plot of the characteristic A1g-E2g Raman modes revealed a compressive strain (ε ≈ -0.78 ± 0.18%) and the coexistence of n- and p-type doped areas in the few-layer MoS2 on SiO2, where the p-type doping is probably due to the presence of residual MoO3. Nanoscale resolution current mapping by C-AFM showed local inhomogeneities in the conductivity of the few-layer MoS2, which are well correlated to the lateral changes in the strain detected by Raman. Finally, characteristic spectroscopic signatures of the defects/disorder in MoS2 films produced by sulfurization were identified by a comparative analysis of Raman and photoluminescence (PL) spectra with CVD grown MoS2 flakes.

[Prenatal diagnosis of central nervous system malformations]. / A központi idegrendszer fejlodési rendellenességeinek praenatalis diagnosztikája.

The prenatal diagnosis of fetal malformations have been the subject of numerous publications in the literature. This has dramatically increased in the last 15 years, mainly due to the advent of high-resolution ultrasound. In addition adequate guidelines issued by professional organizations have encouraged the universal approach to the imaging of fetal anatomy as well as malformations. One of the most significant groups of the fetal anomalies is the central nervous system malformation. Due to its prevalence and severity the praenatal diagnostics of central nervous system malformations got basic significance. In this review we attempted to summarize the recent informations concerning the prenatal diagnostics of the central nervous system anomalies.

[Cervical cancer screening in Hungary--epidemiologic, historical and methodologic aspects]. / Méhnyakszurés Magyarországon--epidemiológiai, történeti és módszertani vonatkozások.

The issue of cervical cancer has been raised again recently, as opposed to other states of the European Union our country shows a high incidence and mortality rate of cervical carcinoma. Although in the 21st century not a single woman should die of cervical cancer, cervical cancer claims the lives of approximately 500 women in Hungary annually until this day. The most typical point of development is where the columnar epithelium of the cervical canal and the squamous epithelium of the uterine cervix meet, the so called transformation zone (squamocolumnar junction). The disease is a several year long process of squamous epithelium metaplasia. This is what provides the opportunity for screening, as by recognizing the lesion in a precancerous state, treatment is possible prior to the development of a tumor. Authors review some epidemiological, historical and methodological issues related to cervical cancer screening.

Effect of a neuroprotective drug, eliprodil on cardiac repolarisation: importance of the decreased repolarisation reserve in the development of proarrhythmic risk.

1. The aim of this study was to analyse the effects of eliprodil, a noncardiac drug with neuroprotective properties, on the cardiac repolarisation under in vitro circumstances, under normal conditions and after the attenuation of the 'repolarisation reserve' by blocking the inward rectifier potassium current (I(K1)) current with BaCl(2). 2. In canine right ventricular papillary muscle by applying the conventional microelectrode technique, under normal conditions, eliprodil (1 microm) produced a moderate reverse rate-dependent prolongation of the action potential duration (7.4+/-1.5, 8.9+/-2.1 and 9.9+/-1.8% at cycle lengths of 300, 1000 and 5000 ms, respectively; n=9). 3. This effect was augmented in preparations where I(K1) was previously blocked by BaCl(2) (10 microm). BaCl(2) alone lengthened APD in a reverse frequency-dependent manner (7.0+/-1.3, 14.2+/-1.6 and 28.1+/-2.1% at cycle lengths of 300, 1000 and 5000 ms, respectively; n=8). When eliprodil (1 microm) was administered to these preparations, the drug induced a marked further lengthening relative to the APD values measured after the administration of BaCl(2) (12.5+/-1.0, 17.6+/-1.5 and 20.5+/-0.9% at cycle lengths of 300, 1000 and 5000 ms, respectively; n=8). 4. In the normal Langendorff-perfused rabbit heart, eliprodil (1 microm) produced a significant QT(c) prolongation at 1 Hz stimulation frequency (12.7+/-1.8%, n=9). After the attenuation of the 'repolarisation reserve' by the I(K1) blocker BaCl(2) (10 microm), the eliprodil-evoked QT(c) prolongation was greatly enhanced (28.5+/-7.9%, n=6). In two out of six Langendorff preparations, this QT(c) lengthening degenerated into torsade de pointes ventricular tachycardia. 5. Eliprodil significantly decreased the amplitude of rapid component of the delayed rectifier potassium current (I(Kr)), but slow component (I(Ks)), transient outward current (I(to)) and I(K1) were not considerably affected by the drug when measured in dog ventricular myocytes by applying the whole-cell configuration of the patch-clamp technique. 6. The results indicate that eliprodil, under normal conditions, moderately lengthens cardiac repolarisation by inhibition of I(Kr). However, after the attenuation of the normal 'repolarisation reserve', this drug can induce marked QT interval prolongation, which may result in proarrhythmic action.