Structure, Morphology, and Crystal Growth of Bacterial Magnetite

Bacterial magnetite particles of anisotropic morphology have been studied by high-resolution transmission electron microscopy. Lattice images of individual crystals are consistent with a well-ordered magnetite cubic inverse spinel structure. The idealized morphology of the biogenic crystals is based on an elongated cubo-octahedral form comprising a hexagonal prism of {111} and {100} faces capped by (1̄1̄1) and (111̄) faces with associated {111} and {100} truncations. Analysis of many particles of diverse size suggests that crystal growth takes place in two stages. The first stage is associated with the formation of well-ordered, isotropic, single-domain crystals of cubo-octahedral morphology. In this stage the crystal length and width develop concurrently up to a size of 20 nm. The second stage involves the anisotropic growth of the isotropic particles along the [112̄] direction. A crystal growth mechanism is postulated which involves the specific nucleation of the (1̄1̄1) face on a surrounding organic membrane. Unidirectional growth then occurs by selective suppression of certain crystallographic axes through spatial and chemical constraints induced by the adjacent organic boundary.

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Sillenites: composition, structure, morphology, crystal growth

Acta Crystallographica Section A Foundations of Crystallography ◽

10.1107/s0108767311081773 ◽

2011 ◽

Vol 67 (a1) ◽

pp. C721-C722

Author(s):

T. I. Mel'nikova ◽

G. M. Kuz'micheva ◽

V. B. Rybakov ◽

N. B. Bolotina ◽

A. Cousson

Keyword(s):

Crystal Growth ◽

Structure Morphology ◽

Composition Structure

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Montmorillonite Dendrites

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100052286 ◽

1974 ◽

Vol 32 ◽

pp. 454-455

Author(s):

Necip Güven ◽

Rodney W. Pease

Keyword(s):

Crystal Growth ◽

Growth Mechanism ◽

Growth Front ◽

Morphological Features ◽

Dendritic Crystal ◽

Crystal Growth Mechanism

Morphological features of montmorillonite aggregates in a large number of samples suggest that they may be formed by a dendritic crystal growth mechanism (i.e., tree-like growth by branching of a growth front).

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TEM and cathodoluminescence of precipitates in II-VI semiconductors

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100104509 ◽

1988 ◽

Vol 46 ◽

pp. 488-489

Author(s):

Joanna L. Batstone

Keyword(s):

Crystal Growth ◽

Band Gap ◽

Local Strain ◽

Wide Band ◽

Optoelectronic Device ◽

Wide Band Gap ◽

Bulk Crystal Growth ◽

Transmission Electron ◽

Device Applications ◽

Stoichiometry Control

Interest in II-VI semiconductors centres around optoelectronic device applications. The wide band gap II-VI semiconductors such as ZnS, ZnSe and ZnTe have been used in lasers and electroluminescent displays yielding room temperature blue luminescence. The narrow gap II-VI semiconductors such as CdTe and HgxCd1-x Te are currently used for infrared detectors, where the band gap can be varied continuously by changing the alloy composition x.Two major sources of precipitation can be identified in II-VI materials; (i) dopant introduction leading to local variations in concentration and subsequent precipitation and (ii) Te precipitation in ZnTe, CdTe and HgCdTe due to native point defects which arise from problems associated with stoichiometry control during crystal growth. Precipitation is observed in both bulk crystal growth and epitaxial growth and is frequently associated with segregation and precipitation at dislocations and grain boundaries. Precipitation has been observed using transmission electron microscopy (TEM) which is sensitive to local strain fields around inclusions.

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STM studies of crystal growth

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100086179 ◽

1991 ◽

Vol 49 ◽

pp. 374-375

Author(s):

M. G. Lagally

Keyword(s):

Crystal Growth ◽

Molecular Beam ◽

Chemical Vapor ◽

Sputter Deposition ◽

Field Of View ◽

Scanning Tunneling ◽

Wide Field ◽

Tunneling Microscopy ◽

Wide Field Of View ◽

The One

It has been recognized since the earliest days of crystal growth that kinetic processes of all Kinds control the nature of the growth. As the technology of crystal growth has become ever more refined, with the advent of such atomistic processes as molecular beam epitaxy, chemical vapor deposition, sputter deposition, and plasma enhanced techniques for the creation of “crystals” as little as one or a few atomic layers thick, multilayer structures, and novel materials combinations, the need to understand the mechanisms controlling the growth process is becoming more critical. Unfortunately, available techniques have not lent themselves well to obtaining a truly microscopic picture of such processes. Because of its atomic resolution on the one hand, and the achievable wide field of view on the other (of the order of micrometers) scanning tunneling microscopy (STM) gives us this opportunity. In this talk, we briefly review the types of growth kinetics measurements that can be made using STM. The use of STM for studies of kinetics is one of the more recent applications of what is itself still a very young field.

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Cristal-growth dynamics of n-doped gaAs

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100132352 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1544-1545

Author(s):

Pham V. Huong ◽

Stéphanie Bouchet ◽

Jean-Claude Launay

Keyword(s):

Crystal Growth ◽

Spatial Resolution ◽

Epitaxial Layer ◽

Outer Surface ◽

Gaas Substrate ◽

Structural Modification ◽

Growth Dynamics ◽

Argon Laser ◽

High Anisotropy ◽

Crystal Gaas

Microstructure of epitaxial layers of doped GaAs and its crystal growth dynamics on single crystal GaAs substrate were studied by Raman microspectroscopy with a Dilor OMARS instrument equipped with a 1024 photodiode multichannel detector and a ion-argon laser Spectra-Physics emitting at 514.5 nm.The spatial resolution of this technique, less than 1 μm2, allows the recording of Raman spectra at several spots in function of thickness, from the substrate to the outer deposit, including areas around the interface (Fig.l).The high anisotropy of the LO and TO Raman bands is indicative of the orientation of the epitaxial layer as well as of the structural modification in the deposit and in the substrate at the interface.With Sn doped, the epitaxial layer also presents plasmon in Raman scattering. This fact is already very well known, but we additionally observed that its frequency increases with the thickness of the deposit. For a sample with electron density 1020 cm-3, the plasmon L+ appears at 930 and 790 cm-1 near the outer surface.

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