Variations of paramagnetic defects and dopants in geo-MoS2 from diverse localities probed by ESR.

Exfoliated flakes from molybdenite crystals often still serve as benchmark substrates for two-dimensional MoS2 fundamental and device-oriented research. In this article, results are reported of a multi-frequency electron paramagnetic resonance (EPR) study on a series of natural 2H MoS2 crystals taken from various (seven) geological sites with the intent to explore the variations in quality and properties in terms of occurring paramagnetic point defects, with particular focus on the assessment of the predominant type of impurity dopant. The sample set covers three types of overall doping regimes, i.e., p-type, n-type, and mixed (n-type and p-type parts in one sample). The doping type appears primarily governed by substitutional impurities as evidenced by the observed As and N acceptor (both substituting for S) and Re donor (substituting for Mo) signals. For all p-type specimens, doping is found to be ruled by As where, however, a strong variation is revealed in doping uniformity, which appears not directly correlated with the As dopant density. Without specific precautions taken, surface contamination related EPR signals are observed in virtually all As-excavated geo-MoS2 specimens. While several of these signals are of unassigned origin, two prominent ones are identified, one as concerning oxo-Mo5+ compounds and the other Mn2+ centers. The geo-MoS2 sample with the foremost n-type doping shows, besides the prime Re donor EPR signal, an intense powder-pattern signal, tentatively typified by g∥ = 2.076, g⊥ = 2.253, which is suggested to originate from intercalation-related defects. The results bear out the necessity of rigorous surface cleaning, even including invasive removal of surface layers, to obtain pristine MoS2 parent crystals suitable for enabling exfoliation of high quality flakes.

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.

Control of TiN oxidation upon atomic layer deposition of oxides.

The interfaces of a physical-vapor deposited (PVD)-TiN electrode with atomic-layer deposited (ALD) HfO2 layers were studied using photoelectron spectroscopy with high kinetic energies of photoelectrons enabling nondestructive in-depth chemical profiling and phase analysis. Our results reveal the presence of only TiNxOy at the TiN/ALD-HfO2 interface with no measurable traces of the TiO2 phase. By contrast, the interface formed by ALD of HfO2 on top of PVD TiN contains both TiO2 and TiNxOy compounds and may be compared to an HfO2/TiN interface with intentional ALD TiO2 interlayer (IL) formation prior to HfO2 growth. Pre-growth of ALD Al2O3 IL drastically reduces the TiO2 and TiNxOy amounts present at the HfO2/TiN interface, which can be ascribed to oxygen scavenging from the initially oxidized TiN surface by energetically more favorable Al-O bonds. The present study demonstrates that the amount of TiO2 phase can be effectively controlled, i.e., increased or decreased, during the ALD process enabling engineering of vacancy-mediated processes.

Re-distribution of oxygen at the interface between γ-Al2O3 and TiN.

Interface of TiN electrode with γ-Al2O3 layers was studied using near edge X-ray absorption fine structure, conventional X-ray photoelectron spectroscopy and photoelectron spectroscopy with high energies. Despite the atomic-layer deposited Al2O3 being converted into thermodynamically-stable polycrystalline cubic γ-phase by high-temperature (1000 or 1100 °C) anneal, our results reveal formation of a thin TiNxOy (≈1-nm thick) interlayer at the interface between γ-Al2O3 film and TiN electrode due to oxygen scavenging from γ-Al2O3 film. Formation of the TiO2 was not observed at this interface. As environmental effect, a strong oxidation resulting in formation of a TiO2(1.4 nm)/TiNxOy(0.9 nm) overlayers on the top of the TiN electrode is traced. Development of O-deficiency of γ-Al2O3 is observed and related to the polarization anisotropy due to the preferential orientation of spin states involved in the X-ray absorption in the plane parallel to the surface. Investigation of the TiN electrode reveals the predominantly "stretched" octahedra in its structure with the preferential orientation relative the interface with γ-Al2O3. This anisotropy can be correlated with ≈200 meV electron barrier height increase at the O-deficient TiN/γ-Al2O3 interface as compared to the TiN/γ-Al2O3 barrier formed under abundant oxidant supply condition as revealed by internal photoemission of electrons from TiN into the oxide.

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.

Intrinsic point defects in buckled and puckered arsenene: a first-principles study.

Using first-principles calculations, we study the structural, energetic, and electronic properties of various point defects in arsenene. Stone-Wales defects are found to be thermodynamically favorable and are predicted to be stable at room temperature. Defects are found to significantly influence the electronic properties in buckled phase. In particular, single vacancies generate gap states whereas strain induced states close to the valence and conduction band edges are observed for Stone-Wales and di-vacancy defects. The computed band structures of di-vacancy defects in puckered phase are less disturbed compared to the corresponding band structures in the buckled one. The influence of a hydrogen-rich atmosphere on the electronic properties of defective arsenene is also investigated. Hydrogen termination of mono/di-vacancies is an exothermic process which removes all defect induced gap states.

Correlation of Bandgap Reduction with Inversion Response in (Si)GeSn/High-k/Metal Stacks.

The bandgap tunability of (Si)GeSn group IV semiconductors opens a new era in Si-technology. Depending on the Si/Sn contents, direct and indirect bandgaps in the range of 0.4-0.8 eV can be obtained, offering a broad spectrum of both photonic and low power electronic applications. In this work, we systematically studied capacitance-voltage characteristics of high-k/metal gate stacks formed on GeSn and SiGeSn alloys with Sn-contents ranging from 0 to 14 at. % and Si-contents from 0 to 10 at. % particularly focusing on the minority carrier inversion response. A clear correlation between the Sn-induced shrinkage of the bandgap energy and enhanced minority carrier response was confirmed using temperature and frequency dependent capacitance voltage-measurements, in good agreement with k.p theory predictions and photoluminescence measurements of the analyzed epilayers as reported earlier. The enhanced minority generation rate for higher Sn-contents can be firmly linked to the bandgap reduction in the GeSn epilayer without significant influence of substrate/interface effects. It thus offers a unique possibility to analyze intrinsic defects in (Si)GeSn epilayers. The extracted dominant defect level for minority carrier inversion lies approximately 0.4 eV above the valence band edge in the studied Sn-content range (0-12.5 at. %). This finding is of critical importance since it shows that the presence of Sn by itself does not impair the minority carrier lifetime. Therefore, the continuous improvement of (Si)GeSn material quality should yield longer nonradiative recombination times which are required for the fabrication of efficient light detectors and to obtain room temperature lasing action.

The lead acceptor in p-type natural 2H-polytype MoS2 crystals evidenced by electron paramagnetic resonance.

A low-temperature (T = 1.5-8 K) electron paramagnetic resonance study of p-type 2H-polytype natural MoS2 crystals reveals a previously unreported anisotropic signal of corresponding defect density (spin S = ½) ~5 × 1014 cm-3. For the applied magnetic field B//c-axis, the response is comprised of a single central asymmetric Zeeman peak at zero-crossing g = 2.102(1), amid a symmetrically positioned hyperfine doublet of splitting 6.6(2) G. Field angular observations reveal a two-branch g pattern, indicative of a defect of lower than axial symmetry, likely orthorhombic (C 2v). Based on the signal specifics, it is ascribed to a system of decoupled Pb impurities substituting for Mo, the defect operating as an acceptor, with estimated thermal activation energy >10 meV. Supporting theoretical anticipation, the results pinpoint the conduct of the Pb impurity in layered MoS2.

Impact of point defects on the electronic and transport properties of silicene nanoribbons.

We study the impact of various point defects on the structural, electronic and ballistic transport properties of armchair silicene nanoribbons, using the density functional theory and the non equilibrium Green's function method. The effect of a Stone-Wales defect, an interior/edge vacancy and an edge dangling bond is examined. Our results show that structural imperfections can alter the electronic structure (energy band structure and density of states) of the nanoribbons and can either increase or decrease the ballistic current. The dependence of the transport properties on the position of the defects (sublattice A or B) and on their distance from the contact is also investigated.

[Shockwave lithotripsy in sialolithiasis patients].

Shockwave lithotripsy was performed by various appliances in sialolithiasis patients. The best results were obtained by means of miniature appliances. Lithotripsy proved to be useful safe alternative for sialolithiasis treatment.

[Treatment of significant parotid ducts deformities].

The paper summarizes authors experience in treatment of 14 patients with congenital parotid ducts deformities (megastenon type). The results showed reconstructive surgical treatment to be sufficiently effective in such cases. If restoration of parotid function is not possible one should consider interventions for secretion reduction and duct walls excision.

An electric field tunable energy band gap at silicene/(0001) ZnS interfaces.

The interaction of silicene, the silicon counterpart of graphene, with (0001) ZnS surfaces is investigated theoretically, using first-principles simulations. The charge transfer occurring at the silicene/(0001) ZnS interface leads to the opening of an indirect energy band gap of about 0.7 eV in silicene. Remarkably, the nature (indirect or direct) and magnitude of the energy band gap of silicene can be controlled by an external electric field: the energy gap is predicted to become direct for electric fields larger than about 0.5 V Å(-1), and the direct energy gap decreases approximately linearly with the applied electric field. The predicted electric field tunable energy band gap of the silicene/(0001) ZnS interface is very promising for its potential use in nanoelectronic devices.

[Ultrasound diagnostics in Kuttner syndrome].

The paper describes high-resolution ultrasonic picture of salivary glands in Kuttner syndrome before and after treatment. Ultrasound evaluation proved to be a useful tool for diagnostic, treatment results assessment and choosing adequate treatment option in these patients.

[Correlation of salivary and genital glands].

Based on the experimental data correlation of parotids and genital glands in 24 male rabbits 1.5 months after testectomy (full testectomy, unilateral partial resection and bilateral partial resection) was found out. The findings included hyperplasia, parenchyma atrophy, stromal and periductal sclerosis of the parotids. In the majority of cases in adjacent lymphatic notes hyperplasia of B-zones and devastation of T-zones may also be seen, confirming autoimmune reaction after genital glands injury.

[Antihomotoxic therapy in patients with inflammatory and dystrophic salivary gland diseases].

Traumeel S was used as monotherapy for salivary glands inflammatory and dystrophic disorders. The study showed the drug to be especially efficient by exacerbation of the recurrent disease but the results were poor by indolent disease and on the latter stages of dystrophic disorder. Traumel S may be recommended to be used in combined therapy for salivary glands inflammatory and dystrophic disorders treatment.

[Incidence and mortality of dental diseases in patients with hematological disorders].

The study was conducted in 102 patients with hematological disorders admitted to the Research Center of Hematology. It was concluded that more than 50% of them needed oral surgery procedures requiring multidisciplinary approach.

[Mildronat--treatment of cardio-neurologic pathology in ischemia and hypoxia].

Cerebrovascular pathology has long moved from the category of a single medical problem in the social problem. Progression of vascular lesions of the brain results in significant disability, and in the later stages interfere with the ability to self-service and significantly reduces the quality of life. The key link is ischemic brain damage, or glutamate cascade, which many researchers believe trigger excitotoxic damage and a major cause of neuronal death. One important component of effective control of the effects of ischemic disorders is complex neuro-cytoprotective therapy. To correct for the effects of both acute and chronic ischemia of the brain need to effectively act in several directions simultaneously, normalizing metabolic changes, eliminating the cytokine imbalance transcription violations, reducing the severity of oxidative stress and excitotoxicity.

[Correction of immunological reactivity dysregulation syndrome].

Factors, able to cause the second immunodeficit, are very various: sharp and chronic poisonings, protracted reception of some medicinal preparations, chronic stress and overstrain. The general line of the factors described higher is the complex negative affecting all systems of organism, including on the immune system. In addition, such factors as an ionizing radiation is also rendered electoral ingibiruyuschee operating on immunity, related to oppressing of the system of krovetvoreniya. Second immunodeficity carry coming character and treatment of second immunodeficitov much simpler and more effective as compared to treatment of primary parafunctions immune system. The restoration capabilities of the immune system are great, therefore the removal of reason of immunodeficit, as a rule, results in renewal of immune system.

[Reactive-dystrophic processes in salivary glands (sialoadenoses) running on the background of metabolic syndrome].

Basing upon comprehensive checkup of 82 patients with metabolic syndrome authors made diagnostics of different forms of sialoadenosis in them. The disease proceeded on the background of abdominal adiposity, lipid metabolism derangements, glucose toleration disturbances and diabetes mellitus of the 2nd type with reduction of tissue sensitivity to insulin (insulin resistivity). Results of the fulfilled patient treatment showed that it was necessary to include in the complex of therapeutic measures metformine (glukofagee) producing positive effect upon carbohydrate metabolism and also to normalize the work of glands increasing their secretory activity.