Indirect Characterization Research Articles

Electronic structure evolution in dilute carbide Ge1−xCx alloys and implications for device applications

We present a theoretical analysis of electronic structure evolution in the highly-mismatched dilute carbide group-IV alloy Ge1−xCx. For ordered alloy supercells, we demonstrate that C incorporation strongly perturbs the conduction band (CB) structure by driving the hybridization of A1-symmetric linear combinations of Ge states lying close in energy to the CB edge. This leads, in the ultradilute limit, to the alloy CB edge being formed primarily of an A1-symmetric linear combination of the L-point CB edge states of the Ge host matrix semiconductor. Our calculations describe the emergence of a “quasidirect” alloy bandgap, which retains a significant admixture of indirect Ge L-point CB edge character. We then analyze the evolution of the electronic structure of realistic (large, disordered) Ge1−xCx alloy supercells for C compositions up to x=2%. We show that short-range alloy disorder introduces a distribution of localized states at energies below the Ge CB edge, with these states acquiring minimal direct (Γ) character. Our calculations demonstrate strong intrinsic inhomogeneous energy broadening of the CB edge Bloch character, driven by hybridization between Ge host matrix and C-related localized states. The trends identified by our calculations are markedly different to those expected based on a recently proposed interpretation of the CB structure based on the band anticrossing model. The implications of our findings for device applications are discussed.

Tunable electronic structure in gallium chalcogenide van der Waals compounds

Transition metal monochalcogenides comprise a class of two-dimensional materials with electronic band gaps that are highly sensitive to material thickness and chemical composition. Here, we explore the tunability of the electronic excitation spectrum in GaSe using angle-resolved photoemission spectroscopy. The electronic structure of the material is modified by $\textit{in-situ}$ potassium deposition as well as by forming GaS$_{x}$Se$_{1-x}$ alloy compounds. We find that potassium decouples the top-most tetra-layer of the GaSe unit cell, leading to a substantial change of the dispersion around the valence band maximum (VBM). The observed band dispersion of a single tetralayer is consistent with a transition from the direct gap character of the bulk to the indirect gap character expected for monolayer GaSe. Upon alloying with sulfur, we observe a phase transition from AB to $\text{AA}^{\prime}$ stacking. Alloying also results in a rigid energy shift of the VBM towards higher binding energies which correlates with a blue shift in the luminescence. The increase of the band gap upon sulfur alloying does not appear to change the dispersion or character of the VBM appreciably, implying that it is possible to engineer the gap of these materials while maintaining their salient electronic properties.

The Intricate Dynamics of the Si(3P) + OH(X2Π) Reaction.

The dynamics of the Si(3P) + OH(X2Π) → SiO(X1Σ+,v',j') + H(2S) reaction is investigated by means of the quasi-classical trajectory method on the electronic ground state X2A' potential energy surface in the 10-2-1 eV collision energy range. Although the reaction involves the formation of a long-lived intermediate complex, a high probability for back-dissociation to the reactants is found because of inefficient intravibrational redistribution of energy among the complex modes. At low collision energies, the reactive events are governed by a dynamics with mixed direct/indirect features. As the collision energy increases, the intermediate complex lifetime increases and final state distributions are found to be in reasonable agreement with statistical predictions obtained using the mean potential phase space theory, thus highlighting the indirect character of the process. These rich and puzzling dynamical features are in line with what has been previously observed for the S(3P) + OH(X2Π) reaction.

Interactive Component in Oral Narratives of Preschool Children: on the Formulation of Hypothesis

The article presents an effort to elaborate the hypothesis for the experimental research devoted to interactive component in the oral narratives of preschool children. It is vital for psycholinguistics to reach a close approach to understanding of the essence of narrative processes which have in ontogenesis their own specifics, and according to some researches, these specifics are presented in indirect character of the process of narrative creation by child in the form of his verbal interaction with an adult.
 We assume that in order to reveal the ontogenetic cognitive discursive mechanisms involved in the process of narration, it is necessary to correlate the regularities of the verbal interaction of the participants in the narrative situation with the overall narrative tasks coming up in narrative process.
 Mеthodology, purpose and tasks of the research are determined by experimentally-genetic method (L.S. Vygotsky) put forward as main requirements «differentiation of the analysis of a thing and analysis of the process», «genetic restoration of all moments of the process development». The following of these requirements means a close following of the process of narrative development in its dynamics and the peculiarities of its formation at different stages of child’s development, paying attention to frequency facts as well as facts overcoming the limits of «narrow» phenomenon – narrative text.
 To work out the hypothesis the narrative material of the earlier made experiment with a group of 3 to 7 age children was used in which an adult took a passive part. The task was to tell the story. The material was not subjected to any analysis for the reason of the adult’s presence during the storytelling. The analysis of oral histories with interactive component included the following tasks: a) choose regular sequences of utterances in the dialogic interaction of child and adult; b) define the functional purpose of the adult’s utterance in the course in the child’s storytelling.
 The obtained results show that the adult practically at every step of the child’s age is oriented on the child’s comprehension and analyzing episodes of the history, that is on child’s formation of his mental image of structural and event sequence in history. The results of the analysis enabled us to propose a hypothesis for the next research step in the field. Along the line of this hypothesis, in the verbal ontogenesis the very nature of oral story as a multifaceted phenomenon of the discursive activity of man brings up to the surface the inner mechanisms of narration which have dialogue basis.

Designing a Novel Monolayer β-CSe for High Performance Photovoltaic Device: An Isoelectronic Counterpart of Blue Phosphorene.

Using the first-principles method, an unmanufactured structure of blue-phosphorus-like monolayer CSe (β-CSe) was predicted to be stable. Slightly anisotropic mechanical characteristics in β-CSe sheet were discovered: it can endure an ultimate stress of 5.6 N/m at 0.1 along an armchair direction, and 5.9 N/m at 0.14 along a zigzag direction. A strain-sensitive transport direction was found in β-CSe, since β-CSe, as an isoelectronic counterpart of blue phosphorene (β-P), also possesses a wide indirect bandgap that is sensitive to the in-plane strain, and its carrier effective mass is strain-dependent. Its indirect bandgap character is robust, except that armchair-dominant strain can drive the indirect-direct transition. We designed a heterojunction by the β-CSe sheet covering α-CSe sheet. The band alignment of the α-CSe/β-CSe interface is a type-II van der Waals p-n heterojunction. An appreciable built-in electric field across the interface, which is caused by the charges transfering from β-CSe slab to α-CSe, renders energy bands bending, and it makes photo-generated carriers spatially well-separated. Accordingly, as a metal-free photocatalyst, α-CSe/β-CSe heterojunction was endued an enhanced solar-driven redox ability for photocatalytic water splitting via lessening the electron-hole-pair recombination. This study provides a fundamental insight regarding the designing of the novel structural phase for high-performance light-emitting devices, and it bodes well for application in photocatalysis.

Why is it so rare and random to find pyre sites?

The cremation rite is well-defined in space and time as it is the central part of a series of complex ritual events. Although it is one of the most significant and representative elements of the funeral, yet we know very little about it due to its destructive nature, the scarcity of pyre sites and the indirect character of cremated bones and artefacts found in graves. The two experimental cremations presented in this article, on the one hand, address this rare occurrence of pyre sites. On the other hand, by the detailed documentation of the cremation process and the formation of pyre sites, it is possible to examine in detail several new issues related to the pyre sites. Thus, the shape, orientation, dimension, and structure of the funeral pyre, as well as some moments of the cremation are discussed in detail. Furthermore, the representation of the body and pyre goods after the pyre’s burndown, the movement of artefacts during burning, and the watering of pyre remains, as well as the problem of the mixture are also examined. At the same time, the experimental observations also draw attention, besides the investigational possibilities, to the archaeological limitations of pyre sites.

PATRIOTIC EDUCATION OF YOUTH AS A SOCIO-PEDAGOGICAL PROCESS

The article is devoted to the study of peculiarities of patriotic education of youth as a social-pedagogical process. The special role of socio-pedagogical foundations of patriotic education in the formation of a person as a citizen is highlighted. The focus is on patriotic education of young people, as in the organized, planned and purposeful process of assimilating the personality of national values and norms of culture aimed at the formation of her civic consciousness. The essence of the socio-pedagogical process, the main purpose of which is the rational organization of educational work aimed at the comprehensive development of the child in the context of a specific society, is revealed. Due to the fact that the socio-pedagogical process is carried out in order to solve the problems of socialization, in its content reflects the specificity of this phenomenon. Socialization can be directly (less meaningful, more uncontrollable) and indirect (meaningful, more manageable) character. It has been found out that the social and pedagogical component of patriotic education of young people helps achieve two goals: the success of socialization of younger generations as patriots and self-development as a subject of activity and as an individual. It is noted that the determinants of external influence on the upbringing of the patriotic qualities of the child's personality are the macro-, mesa- and micro-factors of socialization. It is established that the goal of patriotic education is intertwined with the tasks of socialization and individualization of the personality, which consists in developing the positive human qualities of a young person and promoting its adaptation in public life. It is concluded that the patriotic education of youth as a socio-pedagogical process is one of the important factors of the stabilization of society. The patriotic upbringing of youth can be seen as a process of socially controlling socialization, which is carried out in specially created educational organizations that help develop the capacity of a young person, including her abilities, knowledge, patterns of behavior, values, relationships that are positively valuable to the society in which she lives.

Anisotropic optical properties induced by uniaxial strain of monolayer C3N: a first-principles study.

The optical properties, structural properties and electronic properties of a new two-dimensional (2D) monolayer C3N under different strains are studied in this paper by using first-principles calculations. The applied strain includes in-layer biaxial strain and uniaxial strain. The monolayer C3N is composed of a number of hexagonal C rings with N atoms connecting them. It is a stable indirect band gap 2D semiconductor when the strain is 0%. It could maintain indirect semiconductive character under different biaxial and uniaxial strains from ε = −10% to ε = 10%. As for its optical properties, when the uniaxial strain is applied, the absorption and reflectivity along the armchair and zigzag directions exhibit an anisotropic property. However, an isotropic property is presented when the biaxial strain is applied. Most importantly, both uniaxial tensile strain and biaxial tensile strain could cause the high absorption coefficient of monolayer C3N to be in the deep ultraviolet region. This study implies that strain engineering is an effective approach to alter the electronic and optical properties of monolayer C3N. We suggest that monolayer C3N could be suitable for applications in optoelectronics and nanoelectronics.

Multifunctional two-dimensional semiconductors SnP3: universal mechanism of layer-dependent electronic phase transition

Two-dimensional (2D) semiconductors SnP3 are predicted, from first-principles calculations, to host moderate band gaps (0.72 eV for monolayer and 1.07 eV for bilayer), ultrahigh carrier mobility (∼104 cm2 V−1 s−1 for bilayer), strong absorption coefficients (∼105 cm−1) and good stability. Moreover, the band gap can be modulated from an indirect character into a direct one via strain engineering. For experimental accessibility, the calculated exfoliation energies of monolayer and bilayer SnP3 are smaller than those of the common arsenic-type honeycomb structures GeP3 and InP3. More importantly, a semiconductor-to-metal transition is discovered with the layer number N > 2. We demonstrate, in remarkable contrast to the previous understandings, that such phase transition is largely driven by the correlation between lone-pair electrons of interlayer Sn and P atoms. This mechanism is universal for analogues phase transitions in arsenic-type honeycomb structures (GeP3, InP3 and SnP3).

Spontaneous Direct Band Gap, High Hole Mobility, and Huge Exciton Energy in Atomic-Thin TiO2Nanosheet

The quasi-particle band structure, carrier mobility, and optical response of atomic-thin TiO2 nanosheets were accurately predicted with the many-body perturbation theory of G0W0+BSE calculations. The lepidocrocite-type TiO2 exhibits an unexpected direct band gap of 5.3 eV, different from the retaining indirect band gap character in anatase-type TiO2 nanosheet. Because of the dispersive valence band maxima from the strong overlap between O-2p orbitals, an extremely high hole mobility of 1069 cm2 V–1 s–1 was proposed for the lepidocrocite-type TiO2 nanosheet. Including the electron–hole exchange of excitonic effect, our simulations well reproduce the experimental absorption spectra implying a huge exciton binding energy. The strong anisotropic exciton originates from the crystal dependent effective mass in the lepidocrocite-type TiO2 nanosheet due to the asymmetric orbital overlaps. The strongly bound exciton still renders a sufficiently high potential for hydrogen production from aqueous solution, although...

Layer-dependent band alignment of few layers of blue phosphorus and their van der Waals heterostructures with graphene

The structural and electronic properties of few layers of blue phosphorus and their van der Waals heterostructures with graphene were investigated by means of first-principles electronic structure calculations. We study the four energetically most stable stacking configurations for multilayers of blue phosphorus. For all of them, the indirect band-gap semiconductor character, are preserved. We show that the properties of monolayer graphene and single-layer (bilayer) blue phosphorus are preserved in the van der Waals heterostructures. Further, our results reveal that under a perpendicular applied electric field, the position of the band structure of blue phosphorus with respect to that of graphene is tunable, enabling the effective control of the Schottky barrier height. Indeed, for the bilayer blue phosphorene on top of graphene, it is possible to even move the system into an Ohmic contact and induce a doping level of the blue phosphorene. All of these features are fundamental for the design of new nanodevices based on van der Waals heterostructures.

Electronic and optical properties of Ba(1-x)Ca(x) TiO3 and Ba(1-x)Sr(x)TiO3

The effect of Ca and Sr-doping on the structural electronic and optical properties of the cubic Ba1-xCaxTiO3 and Ba1-xSrxTiO3 (x=0.4, 0.6) mixed crystals was investigated using first-principles calculations based on density functional theory (DFT). The calculated band structures based on the optimized geometry of the cell for the solid solutions show an indirect band gap character at M-points, with low energy dispersion along height symmetry directions in the Brillouin zone. The band gaps increase with Ca and Sr concentrations. The total and partial densities of states were analyzed to examine the contribution of different orbitals to the maximum of valence band and the minimum of the conduction band. The optical properties such as reflectivity, energy loss, refractive index and extinction coefficient were studied. #DFT_calculations #band_gap #density_of_states #optical_properties

Effects of hydrostatic pressure and biaxial strains on the elastic and electronic properties of t-C8B2N2

The effects of hydrostatic pressure and biaxial strains on the elastic and electronic properties of a superhard material t-C8B2N2 have been studied using first-principles calculations. The structure is proven to be mechanically and dynamically stable under the applied external forces. All the elastic constants (except C66) and elastic modulus increase (decrease) with increasing pressure and compressive (tensile) biaxial strain εxx. A microscopic model is used to calculate the Vicker's hardness of every single bond as well as the crystal. The hardness of t-C8B2N2 (64.7 GPa) exceeds that of c-BN (62 GPa) and increases obviously by employing pressure and compressive εxx. Furthermore, the Debye temperature and anisotropy of sound velocities for t-C8B2N2 have been discussed. t-C8B2N2 undergoes an indirect to direct bandgap transition when εxx > 2%; however, the indirect bandgap character of the material remains under pressure.

Effects of Biaxial Strains and High Pressure on the Structural, Electronic, and Vibrational Properties of DC‐HgM2Te4 (M = Al, In)

First‐principles calculations are performed to study the effects of biaxial strains and high pressure on the structural, electronic, and lattice dynamical properties of defect chalcopyrite HgM2Te4 (M = Al, In) semiconductors. The evolutions of optimized structural parameters, band‐gap energy, crystal‐field splitting energy, and ‐point phonon frequencies with the biaxial strain and pressure have been analyzed. The optimized lattice parameters are reasonable compared with the existing experimental results. Both compounds undergo an indirect to direct band gap transition under tensile , however, the semiconductors retain their indirect band gap character under pressure. The increasing pressure pushes the crystal‐field‐splitting hole (CH) band downwards; in contrast, the increasing biaxial strain makes the CH band shift upwards, which results in that the crystal‐field splitting energies decrease from positive to negative. The pressure‐induced softness of low‐frequency modes around the X point suggests that both compounds become dynamically instable. Atomic displacement patterns show that the high frequency modes are mainly determined by the vibrations of group‐III cations.

Особенности использования психологических методов для изучения политического восприятия

An article focuses on specific features of the use of psychological methods for the study of political objects. An focus is made on political perception. An author bases her conclusions on the literature as well as on her own studies’ experience. A distinctive feature of political perception is its indirect character. The mass distribution of new channels of political communication leads to the virtualization of politics and the separation of political images from the real interests and everyday practices of citizens. This is reflected in the process of perception, in which unconscious components play a significant role. In this regard, for the study of political images, both at the rational level and on the unconscious, it is necessary to use complex research methods. The following methods will be considered in this article: in-depth interview, projective test, open question survey and fixed association method. They have proved to be effective in studying political phenomena

The Role of Media Communication & Social Networks Influence on the Business Environment in Georgia

Nowadays modern media is very significant in the business success. At present, 90%of consumers always look forthe information on interesting companies (including Facebook or Instagram pages) before purchasing their products/services. Any company is able to be successful thanks to its properly planned marketing strategy. Modern media apply the outcomes of the scientific and technological progress to the maximum extent. This process is characterized by specific peculiarities: (1) the indirect character of media users and business operators; (2) the existence of feedback; (3) a simultaneous interaction of diverse audiences; (4) the message content universality; (5) the frequency information transfer; (6) the regularity; (7) a variety of technical capabilities. These days, the Georgian media are deemed as a powerful means of social activity and comprise a wide range of the latest technologies, viz. computers, video equipment, satellite television and Internet. Their influence on the society and business is the subject of mass media sociology. Currently, most companies communicate with consumers through the social media. In our case, they have chosen Facebook on the Georgian market.

Lateral and Vertical Heterostructures of h-GaN/h-AlN: Electron Confinement, Band Lineup, and Quantum Structures

Lateral and vertical heterostructures constructed of two-dimensional (2D) single-layer h-GaN and h-AlN display novel electronic and optical properties and diverse quantum structures to be utilized in 2D device applications. Lateral heterostructures formed by periodically repeating narrow h-GaN and h-AlN stripes, which are joined commensurately along their armchair edges, behave as composite semiconducting materials. Direct–indirect characters of the fundamental band gaps and their values vary with the widths of these stripes. However, for relatively wider stripes, electronic states are confined in different stripes and make a semiconductor–semiconductor junction with normal band alignment. This way one-dimensinonal multiple quantum well structures can be generated with electrons and holes confined to h-GaN stripes. Vertical heterostructures formed by thin stacks of h-GaN and h-AlN are composite semiconductors with a tunable fundamental band gap. However, depending on the stacking sequence and number of co...

Træbyggede korsgange ved danske klostre

Wooden cloisters at Danish monasteriesVarious studies have shown that most of the cloisters known at Danish monasteries were constructed in the Late Middle Ages. There are several reasons for this. One is that these brick-built cloisters replaced earlier structures of wooden or half-timbered construction. None of the latter cloister types have survived in Denmark, so they have either to be discovered by archaeological excavation or through indications evident on standing monastery buildings.Archaeological excavations have demonstrated the existence of wooden cloisters associated with the monasteries at Ring, Øm, Dalum and Sæby. Postholes were found in the first three instances, while at Sæby there was burnt daub from half-timbering. The latter monastery was founded quite late in the Middle Ages, at a time that saw extensive construction of brick-built cloisters, so perhaps the remains found here derive from a temporary construction phase.At monasteries such as Tvilum, Horsens Franciscan Friary, Vestervig, Ribe Franciscan Friary, Antvorskov, Asmild and Roskilde Our Lady, the archaeological traces suggest the presence of cloisters of wooden or half-timbered construction. These traces are, however, of either an indirect character or are uncertain due to the early dare of the excavations and absent or inadequate reports on the findings.At Skovkloster (Herlufsholm), Børg­lum, Vitskøl and Ribe Dominican Friary, conclusions have been drawn based on standing buildings. For example, in relation to the Romanesque eastern wings, where earlier cloisters, built in lighter materials and preceding a late medieval brick-built structure, could be expected.Wooden cloisters are also a rare occur­rence in other countries, even though it is quite certain that they have existed there to a major extent. As in Denmark, these have almost all become stone-built over time or have disappeared due to age and decay. The three non-Danish examples mentioned in the article have different constructional forms. They can therefore not contribute to elucidating the precise construction of the Danish cloisters. Presumably they were of approximately the same type of construction here in Denmark as that evident the late medieval half-timbered buildings, and furnished with magnificent carved work as on Apostelgården in Næstved.Hans Krongaard KristensenAfdeling for ArkæologiInstitut for Kultur og SamfundAarhus Universitet

Band gap of corundumlike α−Ga2O3 determined by absorption and ellipsometry

The electronic structure near the band gap of the corundumlike $\ensuremath{\alpha}$ phase of ${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ has been investigated by means of optical absorption and spectroscopic ellipsometry measurements in the ultraviolet (UV) range (400--190 nm). The absorption coefficient in the UV region and the imaginary part of the dielectric function exhibit two prominent absorption thresholds with wide but well-defined structures at 5.6 and 6.3 eV which have been ascribed to allowed direct transitions from crystal-field split valence bands to the conduction band. Excitonic effects with large Gaussian broadening are taken into account through the Elliott-Toyozawa model, which yields an exciton binding energy of 110 meV and direct band gaps of 5.61 and 6.44 eV. The large broadening of the absorption onset is related to the slightly indirect character of the material.

Bandgap nature of chalcopyrite ZnXP2 (X = Si, Ge, Sn)

The bandgap nature and near-edge band structure of the chalcopyrite ZnXP2 (X=Si, Ge, Sn) are investigated using the first-principles approaches. For these materials, whereas the valence band maximums are well defined, there are several competing near-extrema at the conduction band-edge. Moreover, the energetically near-degenerate conduction states are usually derived from different electron orbitals, which results in distinct optical properties and thus different bandgap types. A pseudo-direct bandgap, which is related to a weak optical absorption onset, can also be found beside the well-known direct and indirect bandgaps. In this work, we first investigate the fundamental properties of the band-edge electronic states using the density functional theory with the generalized gradient approximation. The origins of bandgap anomaly of the ZnXP2 systems are then analyzed. Finally, we perform the many-body electronic structure calculations for more reliable band orderings. The quasiparticle calculations indicate that whereas ZnSiP2 and ZnSnP2 have a pseudo-direct and a direct bandgap, respectively. However, ZnGeP2 has a bandgap with mixed pseudo-direct and indirect characters.