Multiple length scale growth spirals on metamorphic graphite {001} surfaces studied by atomic force microscopy
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Abstract
The microtopography of {001} surfaces on single crystals of graphite from a Neoproterozoic marble of the Swakop group, near Wlotzkas Baken, western Namibia, has been studied using differential interference contrast (DIC) microscopy and atomic force microscopy (AFM). A unique aspect of the observed surface microtopography is the presence of growth spirals and hillocks on three different length scales. The largest spirals are polygonized and can be seen without magnification. Steps on this feature are roughly 4 μm high and 90 μm apart. The second-order features are hexagonal growth hillocks with an average step height of 1.5 nm and total lateral dimensions of 5-40 μm. The apex of these hillocks coincides directly with the apex of reentrants in the macrosteps of the large spiral. Morphology suggests the formation of these polygonized hillocks by some mechanism other than simple spiral growth. We speculate that these features may be due to pinning of the macrostep by impurities and subsequent formation of the second-order hillocks. The third length-scale features are spirals found on terraces forming the vicinal faces of the second-order hillocks. These spirals have steps that are 6.7 Å high (unit-cell length along [001]) and an average step spacing of 900 Å. These double-layer steps also show some regions with partial step separation into 3.3 Å high monolayer steps. The observed microtopographic features give us insight into the conditions in, and mechanisms by which these graphite crystals formed during carbonate metamorphism. Crystal growth, unrestricted by the surrounding calcite, was from a fluid phase at low graphite supersaturation and was dominated by the spiral growth mechanism. Comparison with theoretical and simulation studies suggests a critical radius for two-dimensional nucleation on the (001) surface on the order of 100 Å.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Study on adsorption of submicrometer gold on kaolinite by quantum chemistry calculations
- Image distortion in scanning probe microscopy
- Multiple length scale growth spirals on metamorphic graphite {001} surfaces studied by atomic force microscopy
- 29Si MAS NMR study of diopside–Ca-Tschermak clinopyroxenes: Detecting both tetrahedral and octahedral Al substitution
- Electron paramagnetic resonance spectroscopic study of synthetic fluorapatite: Part I. Local structural environment and substitution mechanism of Gd3+ at the Ca2 site
- Electron paramagnetic resonance spectroscopic study of synthetic fluorapatite: Part II. Gd3+ at the Ca1 site, with a neighboring Ca2 vacancy
- Determination of the H3BO3 concentration in fluid and melt inclusions in granite pegmatites by laser Raman microprobe spectroscopy
- Analysis of natural H2O + CO2 + NaCl fluid inclusions in the hydrothermal diamond anvil cell
- Thermodynamics of the amphiboles: Ca-Mg-Fe2+ quadrilateral
- Phase boundary between rutile-type and CaCl2-type germanium dioxide determined by in situ X-ray observations
- The nature, formation, and stability of end-member illite: A hypothesis
- Determination of melanterite-rozenite and chalcanthite-bonattite equilibria by humidity measurements at 0.1 MPa
- Pressure-temperature paths from garnet-zoning: Evidence for multiple episodes of thrust burial in the hinterland of the Sevier orogenic belt
- Mineralogical and Mössbauer spectroscopic study of a diopside occurring in the marbles of Andranondambo, southern Madagascar
- Correlations of octahedral cations with OH–, O2–, Cl–, and F– in biotite from volcanic rocks and xenoliths
- H positions in leucophoenicite, Mn7Si3O12(OH)2: A close relative of the hydrous B phases
- Ominelite, (Fe,Mg)Al3BSiO9 (Fe2+ analogue of grandidierite), a new mineral from porphyritic granite in Japan
- Closure in crystal size distributions (CSD), verification of CSD calculations, and the significance of CSD fans
- Icosahedral domain structure of framboidal pyrite
