Molecular Dynamics Studies of Dislocations in CdTe Crystals from a New Bond Order Potential

Cd1-xZnxTe (CZT) crystals are the leading semiconductors for radiation detection, but their application is limited by the high cost of detector-grade materials. High crystal costs primarily result from property non-uniformity that causes low manufacturing yield. While tremendous efforts have been made in the past to reduce Te inclusions / precipitates in CZT, this has not resulted in an anticipated improvement in material property uniformity. Moreover, it is recognized that in addition to Te particles, dislocation cells can also cause electric field perturbation and the associated property non-uniformity. Further improvement of the material, therefore, requires that dislocations in CZT crystals be understood and controlled. Here we use a recently developed CZT bond order potential to perform representative molecular dynamics simulations to study configurations, energies, and mobilities of 29 different types of possible dislocations in CdTe (i.e., x = 1) crystals. An efficient method to derive activation free energies and activation volumes of thermally activated dislocation motion will be explored. Our focus gives insight into understanding important dislocations in the material, and gives guidance toward experimental efforts for improving dislocation network structures in CZT crystals

On the influence of indium addition on the mechanical properties of gallium arsenide at room temperature

Indentations have been performed on (001) faces of indium alloyed GaAs crystals in darkness and under infrared illumination. The Vickers hardness was measured and the dislocation microstructure around the indents observed by high voltage transmission electron microscopy. A softening effect of indium is evidenced by comparison with the Vickers hardness obtained in the same conditions on undoped GaAs. No significant influence of indium on the dislocation microstructure resulting from indentation in darkness is noted. Indentation under infrared illumination does not reveal any macroscopic photoplastic effect; however, a modification of dislocation microstructure is observed. Whatever the experimental conditions, dislocations appear to experience strong lattice friction. The softening effect of indium addition and the enhanced dislocation mobilities under infrared illumination are discussed in the framework of dislocation glide governed by the Peierls mechanism

EXCITATION-ENHANCED DISLOCATION MOBILITY IN SEMICONDUCTORS

Quantitative features of the enhancement effect by either laser light illumination or electron irradiation on the dislocation motion in semiconductors are surveyed. The experiments show that moving dislocations experience a lattice friction which is lowered under excitation. Theoretical analysis based on the kink diffusion model for dislocation motion indicates that the observed reduction in activation energy corresponds to the electronic energy level in the band gap associated with the straight dislocation sites

Peiling biologie in de eerste graad secundair onderwijs (A-stroom) - Eindrapport

see also http://www.ond.vlaanderen.be/dvo/peilingen/secundair/brochure_peiling_biologie.pdfstatus: publishe

In situ TEM study of dislocation mobility in semiconducting materials

In situ straining experiments have been conducted in Toulouse and Grenoble on elemental semiconductors, III-V and II-VI compounds. This article gives a common interpretation of the results obtained, which allows us to discuss the effect of the strength of covalent bonding on the mobility of dislocations under different conditions.Des expériences de déformation in situ de semiconducteurs élémentaires, et de composés III-V et II-VI, ont été réalisées à Toulouse et Grenoble. Cet article donne une interprétation commune des résultats obtenus, ce qui permet de discuter l'effet de la force des liaisons covalentes sur les mobilités des dislocations dans divers cas de figure