Fundamental Differences in Mechanical Behavior between Two Types of Crystals at the Nanoscale

We present differences in the mechanical behavior of nanoscale gold and molybdenum single crystals. A significant strength increase is observed as the size is reduced to 100 nm. Both nanocrystals exhibit discrete strain bursts during plastic deformation. We postulate that they arise from significant differences in the dislocation behavior. Dislocation starvation is the predominant mechanism of plasticity in nanoscale fcc crystals, while junction formation and hardening characterize bcc plasticity. A statistical analysis of strain bursts is performed as a function of size and compared with stochastic models

Electrical properties of fast cooled InSe single crystals

Influence of fast cooling on electrical properties of n-InSe single crystals is investigated for an ingot grown by the Bridgman method. Electrical characteristics and their anisotropy are investigated in the temperature range 80 to 410 K. It is found that fast cooling, as soon as crystallization is completed, of the ingot leads to an increase of the free electron concentration, conductivity along layers, and conductivity anisotropy, as well as to a decrease of the Hall mobility of carriers along layers. The theoretical analysis of the mobility of carriers has shown that space-charge regions underlie the effective mechanism of their scattering

Electrical properties of fast cooled inse single crystals

Influence of fast cooling on electrical properties of n-InSe single crystals is investigated for an ingot grown by the Bridgman method. Electrical characteristics and their anisotropy are investigated in the temperature range 80 to 410 K. It is found that fast cooling, as soon as crystallization is completed, of the ingot leads to an increase of the free electron concentration, conductivity along layers, and conductivity anisotropy, as well as to a decrease of the Hall mobility of carriers along layers. The theoretical analysis of the mobility of carriers has shown that space-charge regions underlie the effective mechanism of their scattering

Um museu de grandes novidades : as relações de trabalho rural e o agronegócio

O presente trabalho visa investigar qual é a extensão da proteção legislativa conferida aos trabalhadores rurais inseridos no agronegócio e os seus limites. Para tanto, inicialmente, investigou-se a lógica de reprodução do capital, sua derivação na forma jurídica e a estruturação do direito do trabalho. Após, buscou-se a origem e a estrutura das relações de trabalho rural, por meio de o arcabouço histórico, econômico e sociológico, analisando as condições estruturais da inserção econômica do campo no Brasil enquanto país dependente exportador, a luz da teoria marxista da dependência. Em um segundo momento, cotejou-se a produção com o contexto social e econômico no qual estava inserida, traçando paralelo com o desenvolvimento do capitalismo no campo, que redundou no que atualmente se conhece como “agronegócio”. O método empregado é o hipotético-dedutivo, utilizando-se como técnica de pesquisa a documentação indireta em fontes primárias e secundárias bibliográficas.The aim of this work was to examine the extent of legal protection enjoyed by rural workers in agribusiness. Therefore, at first, the logic of the reproduction of capital, the derivation of its legal form, and the structuring of labor law were examined. Then, the origin and the structure of rural labor relations were researched by using the historical, economic, and sociological framework, and the structural conditions of agriculture’s integration in Brazil as a commodity export dependent country were analyzed in the light of the Marxist dependency theory. Subsequently, the production was compared to the social and economic context within which it took place, paralleling it to the development of the capitalism in rural areas, which resulted in what it is currently known as “agribusiness”. The method employed was the hypothetico deductive one and the research technique used was indirect documentation in primary and secondary sources

From villains to victims: experiencing illness in Siberian exile

This essay presents the subjective experience of life and sickness for the punished in late Imperial Siberia, and the distinctions the punished made between legitimate and illegitimate forms of punishment. The essay also explores state policies towards the sick punished, and explores how different levels of the Tsarist administration and local Siberian society dealt with the challenge of sick and decrepit exiles. It argues that conditions in Siberian prisons were, in general, worse than those in European Russian prisons in the post-1906 period, and that the experience of exile in eastern Siberia placed it among the most difficult locations for exile. Though neither the state nor the punished regarded illness as an integral part of their punishment, the prevalence of illness and disease compounded the cruelty of sentences

Thickness dependence of the resistivity of Platinum group metal thin films

We report on the thin film resistivity of several platinum-group metals (Ru, Pd, Ir, Pt). Platinum-group thin films show comparable or lower resistivities than Cu for film thicknesses below about 5\,nm due to a weaker thickness dependence of the resistivity. Based on experimentally determined mean linear distances between grain boundaries as well as ab initio calculations of the electron mean free path, the data for Ru, Ir, and Cu were modeled within the semiclassical Mayadas--Shatzkes model [Phys. Rev. B 1, 1382 (1970)] to assess the combined contributions of surface and grain boundary scattering to the resistivity. For Ru, the modeling results indicated that surface scattering was strongly dependent on the surrounding material with nearly specular scattering at interfaces with SiO2 or air but with diffuse scattering at interfaces with TaN. The dependence of the thin film resistivity on the mean free path is also discussed within the Mayadas--Shatzkes model in consideration of the experimental findings.Comment: 28 pages, 9 figure

The influence of transition metal solutes on dislocation core structure and values of Peierls stress and barrier in tungsten

Several transition metals were examined to evaluate their potential for improving the ductility of tungsten. The dislocation core structure and Peierls stress and barrier of $1/2$ screw dislocations in binary tungsten-transition metal alloys (W$_{1-x}$TM$_{x}$) were investigated using first principles electronic structure calculations. The periodic quadrupole approach was applied to model the structure of $1/2$ dislocation. Alloying with transition metals was modeled using the virtual crystal approximation and the applicability of this approach was assessed by calculating the equilibrium lattice parameter and elastic constants of the tungsten alloys. Reasonable agreement was obtained with experimental data and with results obtained from the conventional supercell approach. Increasing the concentration of a transition metal from the VIIIA group, i.e. the elements in columns headed by Fe, Co and Ni, leads to reduction of the $C^\prime$ elastic constant and increase of elastic anisotropy A=$C_{44}/C^\prime$. Alloying W with a group VIIIA transition metal changes the structure of the dislocation core from symmetric to asymmetric, similar to results obtained for W$_{1-x}$Re$_{x}$ alloys in the earlier work of Romaner {\it et al} (Phys. Rev. Lett. 104, 195503 (2010))\comments{\cite{WRECORE}}. In addition to a change in the core symmetry, the values of the Peierls stress and barrier are reduced. The latter effect could lead to increased ductility in a tungsten-based alloy\comments{\cite{WRECORE}}. Our results demonstrate that alloying with any of the transition metals from the VIIIA group should have similar effect as alloying with Re.Comment: 12 pages, 8 figures, 3 table

Electron Transport in n-Type InSe van der Waals Crystals with Co Impurities

Intercalation and doping are promising routes to tune properties of van der Waals (vdW) semiconductors and pave the way for their applications in digital electronics beyond Moore’s law, sensors and spintronics. The indium selenide (InSe) vdW crystal shows great promise for use in next-generation semiconductor technologies. For these applications to be realized, the effects of impurities on properties of InSe must be understood. Here, we present a comparative experimental study of electron transport in n-type InSe semiconductor doped and electrochemically intercalated with magnetic cobalt (Co) impurities. It is shown that the presence of Co decreases the free electron density, the Hall mobility along layers and the conductivity anisotropy σ⊥C/σ‖C. Furthermore, this leads to a change of the behavior of σ⊥C(T) dependence from a metallic one in pristine samples to a semiconducting one in samples with Co. We also demonstrate that the interaction of electrons with space-charge regions is an effective scattering mechanism, which should be taken into account in doped and intercalated crystals. The present work is important for the basic physics knowledge of the effect of Co impurities on physical properties of InSe, which is needed to tailor the parameters of this semiconductor for applications in electronics and spintronics

Charge Carrier Transport in Van Der Waals Semiconductor InSe Intercalated with RbNO3 Probed by Direct Current Methods

Layered van der Waals (vdW) semiconductors show great promise to overcome limitations imposed by traditional semiconductor materials. The synergistic combination of vdW semiconductors with other functional materials can offer novel working principles and device concepts for future nano- and optoelectronics. Herein, we investigate the influence of the intercalation of semiconducting n-type InSe vdW crystals with ferroelectric rubidium nitrate (RbNO3) on the transport of charge carriers along and across the layers. The apparent maxima in the temperature dependences of the Hall coefficient are explained in the framework of a model that predicts, along with three-dimensional carriers, the existence of two-dimensional ones contributing only to the conductivity along the layers. The revealed increase of the conductivity anisotropy and its activation variation with temperature, which is mainly due to a decrease of the conductivity across the layers, confirm a two-dimensionalization of electron gas in n-InSe after insertion of the ferroelectric. From the numerical analysis, we determined the densities of carriers of both types, concentrations of donors and acceptors, as well as the value of the interlayer barrier