Effect of growth conditions on incorporation of Si into Ga and As sublattices of GaAs during molecular-beam epitaxy

The effect of dopant concentration and growth-surface crystallographic orientation on the incorporation of Si into Ga and As sublattices was investigated during GaAs molecular-beam epitaxy. The epitaxial layers (epilayers) were grown on GaAs substrates with (100), 2°(100), 4°(100), and 8°(100) orientations at a temperature of 520°C and with (111)A, 2°(111)A, 2°(111)A, 5°(111)A, 6°(111)A, and 8°(111)A (where A = Ga) orientations at a temperature of 480°C. The Sidopant concentration was varied within 10¹⁷–10¹⁹ cm^?3. Through electrical and photoluminescent methods of investigation, the Si impurity was found to occur at the sites of both GaAs-layer sublattices not only as simple donors and acceptors (Si_Ga and Si_As), but also as Si_Ga-Si_As, Si_Ga-V_Ga, and Si_As-V_As complexes. The concentration of Si impurity in various forms depends on the doping level of the layers and on the growth-surface orientation. Amphoteric properties of Si manifest themselves more prominently on the (111)A face than on the (100) one. It is shown that impurity defects form at the stage of layer crystallization and depend on the growth-surface structure.     

Metal protection by anticorrosion papers in humid tropical climate

Results of 3-year full-scale field climatic tests on application of five types of inhibiting papers for anticorrosion protection of ferrous and nonferrous metals during storage in a humid tropical climate have been carried out by the Joint Russian and Vietnamese Tropical Research and Technology Center and presented here. It has been shown that the inhibiting paper IPCAS-118 can be recommended for anticorrosion protection of equipment made of steel, copper, and aluminum during 3-year storage in sheds in humid tropical climate conditions     

Theoretical and experimental studies of surface processes in the course of molecular-beam epitaxy of gallium nitride

Semiconductors - The method of atomic-force microscopy has been used to experimentally study the effect of growth conditions on the structure of the surface of epitaxial GaN layers grown by...     

Determination of the fractal dimension for the epitaxial <Emphasis Type="Italic">n</Emphasis>-GaAs surface in the local limit

Atomic-force microscopy studies of epitaxial n-GaAs surfaces prepared to deposit barrier contacts showed that major relief for such surfaces is characterized by a roughness within 3–15 nm, although “surges” up to 30–70 nm are observed. Using three independent methods for determining the spatial dimension of the surface, based on the fractal analysis for the surface (triangulation method), its section contours in the horizontal plane, and the vertical section (surface profile), it was shown that the active surface for epitaxial n-GaAs obeys all main features of behavior for fractal Brownian surfaces and, in the local approximation, can be characterized by the fractal dimension D _f slightly differing for various measuring scales. The most accurate triangulation method showed that the fractal dimensions for the studied surface of epitaxial n-GaAs for measurement scales from 0.692 to 0.0186 μm are in the range D _f = 2.490?2.664. The real surface area S _real for n-GaAs epitaxial layers was estimated using a graphical method in the approximation δ → 0 δ is the measurement scale parameter). It was shown that the real surface area for epitaxial n-GaAs can significantly (ten times and more) exceed the area of the visible contact window.     

Diffusion separation of hydrogen from gas mixtures

Experiments are described and a model is evaluated for the process of production of superpure hydrogen from mixtures with ammonia and nitrogen by selective diffusion through thin metallic membranes.Notation j_H, j_C molar fluxes of hydrogen and ballast gas - k effective permeability coefficient (product of hydrogen solubility coefficient times diffusion coefficient, divided by membrane thickness) - l, L coordinate measured along supply channel and maximum value thereof (channel length) - M molecular weight of hydrogen - P working perimeter of diffusion cell - p, p pressure in supply and output channels - Q, Q_H mixture flow rate and hydrogen output for one cell or entire unit - S area of working section of supply channel - v velocity in output channel - x, x_o molar fraction of hydrogen in mixture and value thereof at inlet - z, Z dimensionless coordinate and length of apparatus - , dimensional and dimensionless hydraulic resistance coefficients - , _* dimensionless pressure in output channel and value thereof at outlet - dimensionless pressure (concentration) of hydrogen in supply channel - hydrogen density in output channel - relative output Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 47, No. 1, pp. 100–108, July, 1984.     

Unconscious emotions: quantifying and logging something we are not aware of

Lifelogging tools aim to precisely capture daily experiences of people from the first-person perspective. Although there have been numerous lifelogging tools developed for users to record the external environment around them, the internal part of experience characterized by emotions seems to be neglected in the lifelogging field. However, the internal experiences of people are important and, therefore, lifelogging tools should be able to capture not only the environmental data, but also emotional experiences, thereby providing a more complete archive of past events. Moreover, there are implicit emotions that cannot be consciously experienced, but still influence human behaviors and memories. It has been proven that conscious emotions can be recognized from physiological signals of the human body. This fact may be used to enhance life-logs with information about unconscious emotions, which otherwise would remain hidden. On the other hand, it is not clear if unconscious emotions can be recognized from physiological signals and differentiated from conscious emotions. Therefore, an experiment was designed to elicit emotions (both conscious and unconscious) with visual and auditory stimuli and to record cardiovascular responses of 34 participants. The experimental results showed that heart rate responses to the presentation of the stimuli are unique for every category of the emotional stimuli and allow differentiation between various emotional experiences of the participants.     

Study of protective properties of polymeric coatings for portable solarcell arrays of the BSA-R type in tropical climate conditions

The influence of factors of the tropical climate of Vietnam on a variation of functional properties of polymeric coatings for portable solarcell arrays has been studied by 12-month-long tests on the base of the Russian-Vietnamese Tropical Research and Technology Center. As a whole, full-scale environmental tests have shown that the new modifications of film materials proposed for face and rear protective coatings are superior in climatic resistance characteristics and parameter stability to the materials applied for these purposes earlier. The adhesive film Radeva-2AM and the film BSP are recommended for application in moist, tropical climates. Original Russian Text ? A.A. Polisan, I.S. Persits, V.N. Ivonin, Chin’ Kuok Kkhan’, V.A. Karpov, 2008, published in Korroziya: Materialy, Zashchita, 2007, No. 4, pp. 30–37.     

Study of the properties of the surface of gallium arsenide by scanning atomic force microscopy

Using the method of atomic force microscopy, complex studies of the profile, potential distribution φ(x,y), and distributions of the phase contrast of the surface of n-GaAs subjected to various types of chemical treatment are carried out. The distribution of the potential and phase contrast at a microlevel, in general, correlates with the profile character. The surface treated in the solution H₂SO₄: H₂O = 1: 10 is characterized by a high degree of nonuniformity with an average roughness of the main profile Δh≈ 10 nm. A considerable part of the surface is covered by hills 20–60 nm in height and 100–500 nm in diameter forming a specific substructure, which correspond to potential jumps as large as 50–60 mV against a general background of 0.77–0.80 V. At a nanolevel, correlation between the profile and phase contrast is clearly pronounced, but no correlation is found between the profile and potential distribution. Treatment of the surface of n-GaAs in a concentrated aqueous NH₄OH solution leads to a decrease in the value of φ(x,y) by ～0.2 V, and in its roughness by more than an order of magnitude (～0.75 nm). The distribution of the profile and phase contrast over the surface is close to the ideal Gaussian distribution for relatively small areas of the surface (200 × 200 nm²). As the area increases, deviation from the Gaussian distribution becomes substantial because of smooth variation in the potential over the contact area. Conservation of the Gaussian character of the surface profile and a simultaneous rise in the average level of the roughness with an increase in the analyzed area indicates the fractal mechanism of formation of the surface profile.     

Submicron free-chromate chemical conversion coatings on AMg-3 aluminum alloy

Coatings obtained in solutions of permanganates are known alternatives to thin chromate conversion coatings on aluminum alloys. However, permanganate ion is an insufficiently effective corrosion inhibitor for aluminum in the acidic medium, and, therefore, modified additives are introduced into converting solutions based on it. The present research is devoted to studying the corrosive characteristics of coatings produced by chemical oxidation in the IFKhANAL-2 permanganate composition and its modifications on AMg-3 aluminum alloy. It is shown that iron and nickel salts are most effective as modified additives and subsequent filling of produced coatings in corrosion inhibitor solutions increases their protective properties up to the level of standard chromate coatings. The researched coatings provide protection for 1.5 years under conditions of a humid tropical climate.     

Enacting archetypes in movies: grounding the unconscious mind in emotion-driven media

Abstract

The concept of emotion-driven media integrates affective computing into developing new types of digital media by including the human spectator as an essential part of the whole system. Enactive media, as a landmark in this direction, provides a theoretical basis that is rooted in the enactivist approach in cognitive science. Based on this thesis, it is required to establish a practical procedure for developing the media content through integrating psychological approaches. We demonstrate a systematic approach for developing the content for emotion-driven media. The theory of archetypes, one of the psychoanalytical approaches, was applied for editing movie clips as the media content, and coupled the content with emotional responses by using experimental psychological methodologies. The results showed that it is promising to utilise archetypal movie clips as the content of emotion-driven media and archetypal symbolism can be a useful resource for developing the content of media systems.