Dislocations around precipitates in AlGaN epilayers

2002 ◽  
Vol 17 (8) ◽  
pp. 2007-2011 ◽  
Author(s):  
Junyong Kang ◽  
Shin Tsunekawa ◽  
Atsuo Kasuya
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Shear Stress ◽  
Dislocation Loop ◽  
Edge Dislocation ◽  
Concentration Change ◽  
Homogeneous Shear ◽  
Transmission Electron ◽  
Shape And Size ◽  
Chemical Force

Dislocations around precipitates in undoped AlGaN were investigated by transmission electron microscopy. The dislocation images were taken under different diffraction conditions. The dislocations are classified into two types, a pure edge dislocation loop and a close-;coiled helical dislocation. Both types of dislocations were found to depend on the shape and size of the precipitate sources. It is suggested that the pure edge dislocation loop results from homogeneous shear stress and the close-;coiled helical dislocation is caused by spherically symmetrical stress concentration at round ends of the precipitates and chemical force due to defect concentration change.

scholarly journals Noncovalent Functionalization of Graphene in Suspension

2013 ◽  
Vol 2013 ◽  
pp. 1-7
Author(s):  
Wenzhi Yang ◽  
Sultan Akhtar ◽  
Klaus Leifer ◽  
Helena Grennberg
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Polar Solvent ◽  
Graphite Foil ◽  
Solid Supports ◽  
Absorption And Fluorescence Spectroscopy ◽  
Transmission Electron ◽  
Noncovalent Functionalization ◽  
Pyrene Derivatives ◽  
Shape And Size

Suspensions of graphene, prepared from graphite foil by sonochemical exfoliation, have been treated with new nonpolar pyrenebutyric amides. The assemblies, in suspension and after deposition on solid supports, were characterized by NMR, absorption, and fluorescence spectroscopy and by transmission electron microscopy, where the well-defined shape and size of an appended [60]fulleropyrrolidine unit facilitates TEM detection of the nonstationary molecules. The accumulated evidence, also including direct comparisons of carbon nanotubes treated with pyrene amides under the same conditions, proves the successful noncovalent functionalization of graphene suspended in non-polar solvent with non-polar pyrene derivatives.

On temperature dependence of deformation mechanism and the brittle–ductile transition in semiconductors

1999 ◽  
Vol 14 (7) ◽  
pp. 2783-2793 ◽  
Author(s):  
P. Pirouz ◽  
A. V. Samant ◽  
M. H. Hong ◽  
A. Moulin ◽  
L. P. Kubin
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Shear Stress ◽  
Deformation Mechanism ◽  
Low Temperatures ◽  
Partial Dislocations ◽  
Brittle Ductile Transition ◽  
Transmission Electron ◽  
Literature Evidence ◽  
Critical Resolved Shear Stress

Recent deformation experiments on semiconductors have shown the occurrence of a break in the variation of the critical resolved shear stress of the crystal as a function of temperature. These and many other examples in the literature evidence a critical temperature at which a transition occurs in the deformation mechanism of the crystal. In this paper, the occurrence of a similar transition in two polytypes of SiC is reported and correlated to the microstructure of the deformed crystals investigated by transmission electron microscopy, which shows evidence for partial dislocations carrying the deformation at high stresses and low temperatures. Based on these results and data in the literature, the explanation is generalized to other semiconductors and a possible relationship to their brittle–ductile transition is proposed.

Epitaxial Growth of NiSi2 on (011)Si

1983 ◽  
Vol 25 ◽  
Author(s):  
L.J. Chen ◽  
W.T. Lin ◽  
M.B. Chang
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Shear Stress ◽  
Epitaxial Growth ◽  
Expected Value ◽  
Edge Type ◽  
Average Spacing ◽  
Transmission Electron ◽  
Interfacial Dislocations ◽  
Critical Resolved Shear Stress

ABSTRACTEpitaxial growth of NiSi2 on (011)Si was investigated by the transmission electron microscopy. Both epitaxial and twin related NiSi2 were formed, with the former being predominant, in samples annealed at 850°C for 1/2 h. The silicides were faceted with {111} interfaces being more prominent than {100} interfaces. Interfacial dislocations were found to be of edge type with 1/6<112> Burgers vectors. The average spacing is about 700 Å which is very close to the theoretically expected value 670 Å.The absence of twins formed on (111) and (111) planes for (011) samples as well as the results obtained for (001) and (111) specimens suggest that there exists a critical resolved shear stress at the interface for the initiation of the formation of twin related NiSi2.

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