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The Seebeck coefficient is the most widely measured property specific to thermoelectric materials. There is currently no consensus on measurement protocols, and researchers employ a variety of techniques to measure the Seebeck coefficient. The implementation of standardized measurement protocols and the use of reliable Seebeck Coefficient Standard Reference Materials (SRMs® ) will allow the accurate interlaboratory comparison and validation of materials data, thereby accelerating the development and commercialization of more efficient thermoelectric materials and devices. To enable members of the thermoelectric materials community the means to calibrate Seebeck coefficient measurement equipment, NIST certified SRM® 3451 "Low Temperature Seebeck Coefficient Standard (10K to 390 K)". Due to different practical requirements in instrumentation, sample contact methodology, and thermal stability, a complementary SRM® is required for the high temperature regime (300K to 900 K). The principal requirement of a SRM® for the Seebeck coefficient at high temperature is thermocyclic stability. We therefore characterized the thermocyclic behavior of the Seebeck coefficient for a series of candidate materials: constantan, p-type single crystal SiGe, and p-type polycrystalline SiGe, by measuring the temperature dependence of the Seebeck coefficient as a function of 10 sequential thermal cycles, between 300K and 900 K. We employed multiple regression analysis to interpolate and analyze the thermocyclic variability in the measurement curves. © 2014 AIP Publishing LLC. [ABSTRACT FROM AUTHOR]

We generalize in this work the constitutive model for silicon crystals of Alexander and Haasen. Strain-rate and temperature dependency of the mechanical behavior of intrinsic crystals are correctly accounted for into stage I of hardening. We show that the steady-state of deformation in stage I is very well reproduced in a wide range of temperature and strain rate. The case of extrinsic crystals containing high levels of dissolved oxygen is examined. The introduction of an effective density of mobile dislocations dependent on the unlocking stress created by oxygen atoms gathered at the dislocation cores is combined to an alteration of the dislocation multiplication rate, due to pinning of the dislocation line by oxygen atoms. This increases the upper yield stress with the bulk oxygen concentration in agreement with experimental observations. The fraction of effectively mobile dislocations is found to decay exponentially with the unlocking stress. Finally, the influence of oxygen migration back onto the dislocations from the bulk on the stress distribution in silicon bars is investigated. [ABSTRACT FROM AUTHOR]

The mechanical strength of bulk single crystal wurtzite ZnO was investigated at elevated temperatures by means of compressive deformation. The yield stress of ZnO in the temperature range of 650–850 °C was found to be around 10–20 MPa, i.e., extremely lower than that of GaN, a typical wide band-gap semiconductor. On the basis of the observed temperature dependence of yield stress, the activation energy for dislocation motion at elevated temperatures in ZnO is deduced to be 0.7–1.2 eV, which follows the relation of activation energy for dislocation motion versus band-gap energy known in a variety of semiconductors. [ABSTRACT FROM AUTHOR]

Heavily impurity-doped single crystals of SixGe1-x alloy with the composition 0.84

Focuses on a study which investigated the alpha and beta dislocations' dynamic behavior in undoped and impurity-doped InAs crystals, using the etch pit technique. Structure of the III-V compound semiconductor crystals; Details on the dislocation velocity; Expression of the measurement of the velocities; Results of the study.

Abstract: A high purity Si x Ge1−x alloy (x 0=0.89) 48mm in length with a maximum diameter of 25mm was grown by the Czochralski method. Development of the cellular structures was evaluated by observing growth striations in the crystal by means of X-ray topography and optical microscopy. Temporary and fatal cellular structures were detected. Two possible factors were distinguished as being responsible for the origin of the cell formations: an enhancement of the effective growth velocity and a gradual reduction of Si composition. Both factors lead to the occurrence of constitutional supercooling beyond the critical relation between growth velocity and alloy composition. [Copyright &y& Elsevier]

The Vickers hardnesses of 15 semiconductors, namely Si, Ge, SiC, AlN, GaN, GaP, GaAs, GaSb, InP, InAs, InSb, ZnO, ZnSe, ZnTe and CdTe, have been investigated from room temperature to their melting points. The temperature dependences of the Vickers hardness HV of 11 of these semiconductors, namely those with a cubic structure, obey a universal relationship when HV and the temperature T are scaled respectively by the shear modulus G and by Gb3/ kB, with b being the magnitude of the Burgers vector. The scaling rule is the same as that found for the temperature dependence of the critical shear stress τc for the {111}<110> slip system, satisfying the relationship HV = (70-100)τc . [ABSTRACT FROM AUTHOR]

Abstract: The mechanical strengths and dislocation activities in wide band-gap semiconductors SiC, AlN, GaN, ZnO and ZnSe at elevated temperatures are summarized. From investigations by indentation hardness test and compressive deformation, activation energies for dislocation motion are evaluated to be 2–2.7, 0.7–1.2 and 0.5–0.7eV in GaN, ZnO and ZnSe, respectively. Dislocations in II–VI compounds ZnO and ZnSe are essentially mobile. [Copyright &y& Elsevier]

Abstract: Dynamic interaction between dislocations and impurities in Si is investigated by using X-ray topography and the etch-pit technique from the viewpoint of Czochralski growth of Si crystals. Dislocation generation is effectively suppressed by doping of B and co-doping of B and Ge, which is originating in the immobilization of dislocations by preferential segregation of impurities. Dislocation velocity in motion is enhanced by increasing the concentration in B impurities. Change of the lattice parameter due to the impurity doping leads to the generation of misfit dislocations at the seed/crystal interface. [Copyright &y& Elsevier]