Slip band formation during bending of gap wafers

{001} LEC-GaP:S wafers were deformed between 470 °C and 640 °C. {111} slip planes of maximum resolved shear stress were activated. Heights and densities of slip steps have been measured by optical and electron microscopy. At lower temperatures deformation proceeds mainly by growth of step heights whereas at higher temperatures bending is accomplished by the increase of slip band density rather than of height.     

Defect Structure in Te-doped GaAs Single Crystals after Plastic Deformation (II). Dislocation Slip and Cell Formation

At temperatures above the brittle-to-ductile transition (490 °C) in Te-doped GaAs three types of predominant defect configurations have been observed after uniaxial compression along a [001] direction: (i) twins and stacking faults (500 … 520 °C), (ii) slip zones of dislocations (≈550 °C) and (iii) dislocation cells (580 … 590 °C). In Part II quantitative details of the appearance of slip and cell formation are given. Leading segments of gliding half loops are mainly of 60° type. Cell walls were formed by multiple slip of perfect dislocations.     

Gleitbanduntersuchungen während und nach Verformung der intermetallischen Verbindung MgZn2

Measurements of densities, lengths, offsets and velocities of slip bands have been performed by optical microscopy of surfaces of the single crystalline intermetallic compound MgZn₂ plastically deformed at temperatures from 245 to 427°C. From their shear strain dependence conclusions have been drawn concerning the behaviour of dislocations during deformation of this compound completely brittle at room temperature.     

Defect Structure of Strained Heteroepitaxial In(1—x)Al(x)P Layers Deposited by MOVPE on (001) GaAs Substrates

Weak-beam, large angle convergent beam electron diffraction and high resolution transmission electron microscope experiments have revealed, that after strain relaxation due to plastic deformation dislocation networks can be observed in In_(1—x)Al_(x)P heteroepitaxial layers grown on (001) GaAs substrates under compressive stress. The 60° slip dislocations are mostly dissociated into partials of Shockley type whereas in the particular case of layers grown under tension twins are predominantly formed by successive nucleation and slip of 90° Shockley partials on adjacent {111} glide planes lying inclined to the (001) surface. When a few 90° Shockley partials pile up during extension of twins, then planar incoherent twin boundaries with {112} coincidence planes have been formed during strain relaxation. Due to the space group symmetry ((InAl)P belongs to the space group F4-3m) there is a striking asymmetry in defect formation, i.e. defect nucleation and slip on the planes (111) and (1-1-1) slip of the [1-10] zone are preferred to nucleation and slip on the {111} planes of the [110] zone. Apparently, the occupacy of the atomic sites in the dislocation core with either group-III or group-V atoms is responsible for this behaviour. The nature of the defects implies that their spontaneous nucleation should have taken place at the growing surface. Under tensile strain the 90° Shockley partial is nucleated first and the 30° one trails. Under compressive strain this sequence is reversed. It is evident, for dissociated dislocations lying at the interface always the 30° partial, i.e. the partial with less mobility or with higher friction force, is detained near or directly in the interface. Thus, in layers grown under tension the stacking fault associated with the dissociated 60° dislocation lies inside the GaAs substrate. For layers grown under compression it is located inside the ternary layer.     

Application of X-ray diffraction topography for the study of Al single crystals plastically deformed at low temperatures

The Lang method has been used to investigate regularities and peculiarities of formation of Al single crystal dislocation structure in various stages of the stress-strain curve at 77.3 and 4.2°K up to high strains. The low temperature deformation of crystals has been found to cause a sharp localization of the deformation into slip bands that correspond to different glide systems. A comparison with metallography is added.     

Lang method applied to investigation of Al single crystal initial structure and of its effect on the eventual development of plastic strain

The land method was used to study the structure of Al single crystals (99.9997% pure) grown from the melt, the thermal stability and the character of changes in different subgrain structures during work hardening. The method has proved to permit observation of slip development both in the early strain region (where occurs “levelling” of the structure of the bulk under strain), and during concert dislocation movement in specific slip planes up to large strains at 4.2°K.     

Synchrotron X-ray diffraction study of the structure of oral stratum corneum model lipid membranes

Membranes modeling the lipid fraction of the mucous membrane of the human oral cavity have been studied by X-ray synchrotron diffraction. Ternary systems, composed of a mixture of sphingomyelin, dipalmitoylphosphatidylcholine, and dipalmitoylphosphatidylethanolamine with component weight ratios of 1: 2: 2 and 1: 2: 1, have lamellar structures in the gel phase at the physiological temperature (37°C). An inverted hexagonal phase is formed in the system with 40% dipalmitoylphosphatidylethanolamine in the temperature range of 60–70°C. This phase coexists with the liquid-crystalline lamellar phase in a narrow temperature range and completely surpresses the lamellar phase with an increase in temperature to 80°C. Multi-component oral stratum corneum membranes are characterized by several lamellar phases at 20–37°C and the coexistence of one or several lamellar phases with inverted hexagonal phase at 80–90°C.     

Influence of substrate temperature on the structure of ZnO:Al thin films

ZnO: Al films were prepared using low cost spray pyrolysis technique. The dependence of the physical properties on the substrate temperature was studied. The best films obtained at 500°C substrate temperature with preferred [002] orientation. The sheet resistance decreases with increased substrate temperature, and values as low as R_sh = 207 Ω/cm² are reached for substrate temperature of 500°C. The optical transmittance of films increased by increasing the substrate temperature and received to 75% at 500°C. (© 2007 WILEY ‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Dislocation energy levels in deformed silicon

Abstract-Energy levels in deformed silicon have been directly measured by transient junction capacitance techniques. If complex slip band formation is not suppressed, a large variety of states are observed after deformation with a prominent state at E_v − 0.68 ev. After annealing at 900°C the complex defect spectra simplify to two dominant states at E_v + 0.35 ev and E_c − 0.38 ev. In more homogeneously deformed silicon where slip band formation is suppressed, the dominant state at E_c − 0.68 ev is not observed after deformation and the spectra resembles that obtained after annealing the complex spectra at 900°C.     

Defect Structure in Te-doped GaAs single Crystals after Plastic Deformation (I). Twins and Stacking Faults

At temperatures above the brittle-to-ductile transition (490 °C) in Te-doped GaAs three types of predominant defect configurations have been observed after uniaxial compression along a [001] direction: (i) twins and stacking faults (500 … 520 °C), (ii) slip zones of dislocations (≈ 550 °C) and (iii) dislocation cells (580 … 590 °C). In Part I quantitative details of the appearance of twins and stacking faults are given. Most frequently found were 30° partials in twins and stacking faults.     

The recovery of Quenched-in Vacancies in Fe–Al (6.3 to 28.3 at.%) Alloys studied by Positron Annihilation

Measurements of the peak height of the 2γ-angular correlation curve were carried out during constant rate heating of Fe–Al alloys with an Al-content between 6.3 and 28.3 at.%. The samples had been quenched form 1000°C into water at room temperature. Two recovery stages are observed. The first stage at 100 to 200°C shows a small decrease of the peak height. The main stage at 300 to 400°C is attributed to the migration and disappearance of monovacancies. From isothermal measurements the migration enthalpy of vacancies is estimated to (1.15 ± 0.1) eV in Fe–Al (19.9 at.%) and to (1.31 ± 0.1) eV in Fe–Al (24.4 at.%). – In samples with an Al-content between 13.8 and 28.3 at.% a minimum in the peak height at 400°C is found. Obviously a particular stage is formed in these samples during migration of quenched-in vacancies. Possible causes of the effect are discussed.     

Structural and Electrical Properties of Cd Doped InSe Thin Films

Polycrystalline Cd doped InSe thin films were obtained by thermal co‐evaporation of alpha‐In₂Se₃ lumps and Cd onto glass substrates at a temperature of 150°C. The films were annealed at 150°C and 200°C. The films were found to contain around 46% In, 47% Se and 7% Cd in weight. The films exhibited p‐type conductivity. The results of conductivity measurements have revealed that thermionic emission and variable range hopping are the two dominant conduction mechanisms, in the temperature ranges of 320‐160 K and 150‐40 K respectively. It was observed that above 240 K mobility is limited by the scattering at the grain boundaries. As the temperature decreases, thermal lattice scattering followed by the ionized impurity scattering dominate as the two main mechanisms controlling the mobility. Acceptor to donor concentration ratio was found to be slightly increasing due to annealing.     

Re-determination of the temperature of the coherent spinodal curve in an-Al-15 at.% Zn alloy by transmission electron microscopic and hardness investigations

The character of the coarsening of the concentration modulations is studied in an Al-15 at. % Zn alloy applying TEM investigations (TEM micrographs and diffraction patterns) and hardness measurements in the temperature range from 40 °C to 130 °C. From the TEM investigations the temperature of the coherent spinodal curve is estimated to be (93 ± 7)°C. This value agrees fairly well with the result obtained by means of hardness measurements (kink in the TTT-curve occurring at about (84 ± 3) °C). The TEM observations of structure revealed in the T_a-range below the coherent spinodal a periodic structure relevant to spinodal decomposition. The periodicity of modulations is confirmed by electron diffraction patterns where a clear effect of sidebands near the matrix spots is observed.     

Thermal Analysis of LiGaO2 and NaGaO2

The high-temperature thermal properties of the ternary oxides LiGaO₂ and NaGaO₂ are studied by simultaneous differential thermal analysis and thermogravimetry between room temperature and about 1700 °C. For the melting temperature of LiGaO₂ a value of 1595 ± 10 °C is determined. NaGaO₂ undergoes a solid state phase transition at 1280 ± 10 °C and melts at 1395 ± 10 °C.     

The Description of the Isothermal Decomposition Processes in Al?Sc Alloys by means of Electric Resistivity Measurements and TEM Investigations

The decomposition behaviour of two AlSc alloys (c_Sc = 0.18; 0.36 at.%) after direct quench to room temperature and subsequent ageing at temperatures in the range 200 °C ≦ T_a ≦ 550 °C was investigated by means of isothermal resistivity measurements and TEM. In the temperature range 325 °C ≦ T_a ≦ 400 °C both alloys show independent of the Sc content an “inversion” of the decomposition kinetics, obviously caused by the transition of the coherent into the incoherent Al₃Sc phase.     

Investigations of phase relations and eutectic directional solidification on the NiAl-V join

The NiAl-V join was investigated out to 45 at % vanaduim and the two-phase nature of the alloys formed indicates that a true binary exist with a eutectic at 40 ± 2% vanadium. The eutectic temperature was determined by optical methods to be 1350°C (1360°C was indicated by DTA). Directional solidification of the NiAl-V eutectic composition produced a structure which is lamellar, with interlamellar sapcing of λ = 4.2 μm at a solidification rate R = 1.5 cm/h.     

Study of dielectric permeability and dielectric loss angle tangent of triglycine selenate depending on the conditions of growing

Triglycine selenate (TGSe) monocrystals were grown at constant temperature and constant supersaturation. Dielectric permeability and the dielectric loss (angle tangent) of TGSe were studied both in weak and in strong electric fields with growing conditions. It was stated that the Curie temperature is 22,5° ± 0,1°C. The Curie-Weiss temperature differs by 2–3,5° from the temperature corresponding to the maximum value of dielectric permeability. Nonlinearity of TGSe is determined.     

Addition effects of bismuth oxide on Samaria-doped ceria based lithium carbonate composite electrolytes for intermediate temperature-solid oxide fuel cells

ABSTRACT

The effect of amounts (3, 5, 10, 20 wt%) of Bi₂O₃ on the sintering characteristics and porosity of Samaria-doped Ceria (SDC) based Lithium carbonate has been evaluated. The density had a maximum as high as 98.5% of theoretical density at 800°C with only 1wt%Li₂CO₃ and 3 wt%Bi₂O₃. The composite electrolytes showed high ion conductivity at evaluated temperatures. Composition and calcination temperature were found to affect the morphology and conductivity of the composite electrolytes greatly. The total conductivity closed to 3 orders of magnitude greater than pure SDC at operating temperature of 900°C and 3.5 orders of magnitude greater than pure SDC at operating temperature of 600°C. Especially, the best sample containing 3 wt% Bi₂O₃ sintered at 800°C for 2 h which had an ionic electrical conductivity of 0.17S cm^?1. According to fuel cell performance, these composite electrolytes are chemically stable, which is an attractive prospect in intermediate temperature solid oxide fuel cell applications.     

Properties of a-Si:H prepared by the photochemical decomposition of Si2H6

High quality a-Si:H films have been prepared by the direct photolysis of disilane at a substrate temperature below 350 °C. The growth rate is independent of substrate temperature for both undoped and phosphorus doped films, while it is thermally activated and dramatically enhanced by boron doping. The hydrogen content decreases from 7 to 2 at.%, as deposition temperature is varied from 200 to 300 °C. The photoconductivity as high as 3.7 × 10^?4 Ω^?1cm^?1 (AM1 100 mW/cm²) has been obtained and no light soak degradation was observed.     

Dielectric and thermal behaviour of holmium tartrate trihydrate crystals

Measurements on dielectric constant of holmium tartrate trihydrate crystals at frequencies of the applied a.c. in the range 1 kHz to 1 MHz and at temperature in the range 30°C to 330°C are reported. The dielectric constant ε′ increases with temperature at all frequencies, attains a peak near 250°C, and then decreases as the temperature goes beyond 250°C. The anomalous dielectric behaviour at near about 250°C is attributed to be as a result of crystallographic/polymorphic phase transition brought about in the material. The results on the dielectric behaviour of the material are supplemented by results of thermal analysis viz., TG and DTA. Thermogravimetric and differential thermal analytic techniques have been used to study thermal behaviour of the material. It is shown that the material is thermally stable up to 220°C beyond which it decomposes through three stages till the formation of holmium oxide at 1200°C. The non‐isothermal kinetic parameters e.g., activation energy and the frequency factor have been evaluated for first two stages of thermal decomposition by using the integral method of Coats and Redfern. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)