Downshift of Raman peak in diamond powders

Zhao, Xu; Cherian, K.; Roy, Rustum; White, William Β.

doi:10.1557/jmr.1998.0277

Cited by 30 publications

(19 citation statements)

References 11 publications

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“…The first-order Raman band (F 2g ) of diamond occurs at wavenumber 1332 cm −1 and represents the main C-C bond vibration in diamond. A shift of this Raman peak to lower wavenumbers is a well-known effect occurring at very small crystallite sizes (Zhao et al 1998). It can also vary as a function of lattice stress, presence of lonsdaleite, or of temperature, which, in turn, depends on the incident laser power (Miyamoto 1998).…”

Section: Resultsmentioning

confidence: 99%

Experimental shock synthesis of diamonds in a graphite gneiss

Kenkmann

Hornemann

Stöffler

2005

Meteorit & Planetary Scien

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Experimental shock synthesis of diamonds in a graphite gneissAbstract-The occurrence of diamonds in terrestrial impact craters and meteorites is related to dynamic shock loading during hypervelocity impacts. To understand the mechanism of impact diamond formation in natural rocks, shock-recovery experiments with graphite gneiss were carried out at shock pressures between 35 and 79 GPa. This is the first report on the successful shock synthesis of microdiamonds in a natural rock. Micrometer-size diamonds and a wide range of intermediate, presently unclassified, amorphous, and disordered carbon phases were observed within vesiculated biotite melts in the vicinity of relic graphite grains using microRaman spectrometry. We explain these findings by jetting mechanisms of carbon and graphite clusters, originating at the edges of graphite grains, into the very hot and volatile rich biotitic melt veins during shock loading. This environment enabled the thermally activated crystallization of diamonds during shock compression in a period of less than 0.5 µsec. Regraphitization of diamonds during pressure release was widespread and caused the formation of the amorphous to disordered carbon phases recorded frequently with microRaman spectroscopy. The surviving diamonds must have cooled down to 2000 K during the compression phase at local thermal sinks and cooler interfaces to avoid regraphitization.

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Section: Resultsmentioning

confidence: 99%

Experimental shock synthesis of diamonds in a graphite gneiss

Kenkmann

Hornemann

Stöffler

2005

Meteorit & Planetary Scien

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“…34 Additionally, the peak shifts were observed due to the heating up of a measurement target by probing laser. 13,35,36 In our case, the typical sizes of the crystal grains are larger than 100 nm (see Fig. 2 (b)) which seems to be rather large to discuss the internal stress causing the observed relatively large peak shifts of around 10 cm -1 .…”

Section: Micro-raman Spectrum Of the Grown Particles At Various Condimentioning

confidence: 52%

Synthesis of diamond fine particles on levitated seed particles in a rf CH4/H2 plasma chamber equipped with a hot filament

Shimizu

Thomas

et al. 2012

Journal of Applied Physics

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The first successful growth of diamond layers on levitated seed particles in CH 4 /H 2 plasma is presented. The particles were grown in an rf CH 4 /H 2 plasma chamber equipped with a tungsten hot filament. The seed diamond particles injected in a plasma are negatively charged and levitated under the balance of several forces, and diamond chemical vapor deposition takes place on them. The SEM images show that the crystalline structures are formed after the coagulation of islands. The micro-Raman spectroscopy of the particle grown after several hours show the clear peak assigned to diamond.

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“…The wave number of the Raman-active mode can be shifted toward lower values (down to 1310 cm −1 ) if the laser power used for exciting the Raman effect is increased. Zhao et al [32] have shown that such a shift can also be achieved by decreasing the grain size of diamond crystallites down to a few tens of nanometers. But it is not the case in our experiments.…”

Section: Discussionmentioning

confidence: 99%

Discrimination of metamorphic diamond populations by Raman spectroscopy (Kokchetav, Kazakhstan)

Korsakov

Vandenabeele

Theunissen

2005

Spectrochimica Acta Part A: Molecular and Biomolecular Spectros

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Metamorphic diamond is a powerful but frequently debated indicator for ultrahigh-pressure metamorphic (UHPM) conditions. Because of their small size, their optical identification needs confirmation. Characteristics of chemically extracted microdiamonds from Kokchetav, identified by different analytical methods, are used here for unambiguous in situ identification by Raman microspectroscopy. Differences appear in the diamond spectra and the Raman analytical method is explored as a helpful tool in the discrimination between diamond populations from four different UHPM lithologies of Kokchetav. Not considering the graphite-coated diamond, out of the reach of the laser wavelength used here, the comparison of these Kokchetav Raman spectra may provide additional information in other UHPM studies.

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Downshift of Raman peak in diamond powders

Cited by 30 publications

References 11 publications

Experimental shock synthesis of diamonds in a graphite gneiss

Experimental shock synthesis of diamonds in a graphite gneiss

Synthesis of diamond fine particles on levitated seed particles in a rf CH4/H2 plasma chamber equipped with a hot filament

Discrimination of metamorphic diamond populations by Raman spectroscopy (Kokchetav, Kazakhstan)

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