A mechanical-loading stage operating inside a scanning electron microscopy (SEM) was used to realize the sliding between nested shells of multiwalled carbon nanotubes (MWCNTs). A stick−slip motion and a smooth pullout motion were observed for the two separate MWCNTs studied. A model that includes the shear interaction, the “capillary” effect, and the edge effect, was used to explain the observed sliding between nested shells. The shear strength between shells was determined and the surface energy of the MWCNT shell estimated.

Controlled Sliding and Pullout of Nested Shells in Individual Multiwalled Carbon Nanotubes

Révélation métallographique des défauts cristallins dans InP

Non‐Radiative Transitions in Semiconductors

The elucidation of the effects of structurally extended defects on electronic properties of materials is especially important in view of the current advances in electronic device development that involve defect control and engineering at the nanometer level. This book surveys the properties, effects, roles and characterization of extended defects in semiconductors. The basic properties of extended defects (dislocations, stacking faults, grain boundaries, and precipitates) are outlined, and their effect on the electronic properties of semiconductors, their role in semiconductor devices, and techniques for their characterization are discussed. These topics are among the central issues in the investigation and applications of semiconductors and in the operation of semiconductor devices. The authors preface their treatment with an introduction to semiconductor materials and conclude with a chapter on point defect maldistributions. This text is suitable for advanced undergraduate and graduate students in materials science and engineering, and for those studying semiconductor physics.

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Extended Defects in Semiconductors: Electronic Properties, Device Effects and Structures

A review of etching and defect characterisation of gallium arsenide substrate material

A study was made of n‐type GaAs prepared by liquid‐phase epitaxy doped with Si, Ge, Sn, Te, and Se by photoluminescence and Te‐doped material by transmission‐electron microscopy. A broad emission band centered at 1.2 eV (band B) is observed in LPE materials doped with group VI elements. Band B increases in intensity relative to the bandgap radiation with increasing dopant concentration in the 1018 cm−3 range. It is suggested that the recombination centers responsible for band B are the neutral (VGa+3 Te) complexes postulated by Vieland and Kudman, and that these represent the solid solution of Ga2Te3 in GaAs. With increasing dopant content, the solubility limit is eventually exceeded, and precipitates of this compound are then formed. These have been observed and identified by transmission‐electron microscopy. The radiative efficiency falls off sharply with increasing dopant content beyond 2–3×1018 cm−3 in materials doped with Se and Te. It is suggested that this fall off is partly due to nonradiative rec...

Observations Concerning Radiative Efficiency and Deep‐Level Luminescence in n‐Type GaAs Prepared by Liquid‐Phase Epitaxy

A study was made of the correlation between substrate flaws and the performance of GaAs injection lasers fabricated by liquid‐phase epitaxy. These devices are p+/n structures where the p+ region is deposited epitaxially, followed by heat treatment to displace the p‐n junction about 1–2 μ into the n‐type substrate. The melt‐grown substrates were studied with the aid of transmission electron microscopy, infrared transmission, x‐ray topography, etching studies, and photoluminescence. It is concluded that the dislocation density of the substrate is not the controlling factor in laser performance unless it exceeds 105 cm−2. A dislocation density of 103–104 cm−2 is not excessive. Precipitates and impurity striations in the substrate are probably the most damaging imperfections. In Te‐doped GaAs the presence of Ga2Te3 precipitates is to be avoided. In the case of Si‐doped materials, the precipitation problem appears to be less severe. Nevertheless, small clusters have been detected by electron transmission micro...

C. J. Buiocchi

Papers

Observations Concerning Radiative Efficiency and Deep‐Level Luminescence in n‐Type GaAs Prepared by Liquid‐Phase Epitaxy

Effect of Substrate Imperfections on GaAs Injection Lasers Prepared by Liquid‐Phase Epitaxy