188 research outputs found
Characterization of Fe-N nanocrystals and nitrogen–containing inclusions in (Ga,Fe)N thin films using transmission electron microscopy
Nanometric inclusions filled with nitrogen, located adjacent to FenN (nÂĽ3 or 4) nanocrystals
within (Ga,Fe)N layers, are identified and characterized using scanning transmission electron
microscopy (STEM) and electron energy-loss spectroscopy (EELS). High-resolution STEM images reveal a truncation of the Fe-N nanocrystals at their boundaries with the nitrogen-containing inclusions. A controlled electron beam hole drilling experiment is used to release nitrogen gas from an inclusion in situ in the electron microscope. The density of nitrogen in an individual inclusion is measured to be 1.460.3 g/cm3. These observations provide an explanation for the location of surplus nitrogen in the (Ga,Fe)N layers, which is liberated by the nucleation of FenN (n>1) nanocrystals during growth
Recommended from our members
On the feasibility to investigate point defects by advanced electron microscopy
Transmission Electron Microscopy evolves rapidly as a primary tool to investigate nano structures on a truly atomic level. Its resolution reaches into the sub Angstrom region by now. Together with a better correction of lens aberrations, sensitivities are drastically enhanced. Utilizing advanced electron microscopes, it is feasible to promote experiments that aim to detect single atoms. This enables local investigations of non-stoichiometry. This paper reviews the current state-of-the-art
Recommended from our members
KLaF4 nanocrystallisation in oxyfluoride glass-ceramics
Nanocrystallisation of the cubic and hexagonal polymorphs of KLaF 4 in a 70SiO2-7Al2O3-16K 2O-7LaF3 (mol%) glass has been achieved by heat treatment above the glass transition temperature. For treatment at 580°C, only the cubic structure crystallises, with a maximum crystallite size of ~9 nm. At higher temperatures, crystallisation of the hexagonal structure also takes place. The crystallisation process has been analysed using several thermal and structural techniques and is revealed to occur from a constant number of nuclei. The formation of a viscous barrier which inhibits further crystal growth and limits the crystal size to the nanometric range is observed. The title materials doped with lanthanide ions may be good candidates for optical applications
KLaF4 nanocrystallisation in oxyfluoride glass-ceramics
Nanocrystallisation of the cubic and hexagonal polymorphs of KLaF 4 in a 70SiO2-7Al2O3-16K 2O-7LaF3 (mol%) glass has been achieved by heat treatment above the glass transition temperature. For treatment at 580°C, only the cubic structure crystallises, with a maximum crystallite size of ~9 nm. At higher temperatures, crystallisation of the hexagonal structure also takes place. The crystallisation process has been analysed using several thermal and structural techniques and is revealed to occur from a constant number of nuclei. The formation of a viscous barrier which inhibits further crystal growth and limits the crystal size to the nanometric range is observed. The title materials doped with lanthanide ions may be good candidates for optical applications
Making sense of nanocrystal lattice fringes
The orientation-dependence of thin-crystal lattice fringes can be gracefully
quantified using fringe-visibility maps, a direct-space analog of Kikuchi maps.
As in navigation of reciprocal space with the aid of Kikuchi lines,
fringe-visibility maps facilitate acquisition of 3D crystallographic
information in lattice images. In particular, these maps can help researchers
to determine the 3D lattice parameters of individual nano-crystals, to ``fringe
fingerprint'' collections of randomly-oriented particles, and to measure local
specimen-thickness with only modest tilt. Since the number of fringes in an
image increases with maximum spatial-frequency squared, these strategies (with
help from more precise goniometers) will be more useful as
aberration-correction moves resolutions into the subangstrom range.Comment: 12 pages, 15 figures, 2 tables, 60 refs, RevTex4, notes
http://www.umsl.edu/~fraundor/help/imagnxtl.ht
Production of large graphene sheets by exfoliation of graphite under high power ultrasound in the presence of tiopronin
- …