Temporal and spatial evolution of C2 in laser induced plasma from graphite target

Harilal, S. S.; Issac, R. C.; Bindhu, C. V.; Nampoori, V. P. N.; Vallabhan, C. P. G.

doi:10.1063/1.363229

Cited by 79 publications

(48 citation statements)

References 38 publications

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“…The absorption due to inverse bremsstrahlung, negligibly small at low laser intensities increases exponentially with increasing laser intensity beyond threshold value [23]. The emission intensity of ionized species increases drastically above the threshold laser intensity [13,41]. Once ions and electrons are produced, one can have neutral carbon atoms by three body recombination process of the type C þ þ e þ e ¼ C þ e. However, in the vicinity of the target the temperature of the plume is high and it is the collision processes, C þ e ¼ C þ þ e þ e that predominate over the recombination and hence we see excited C 2 away from the target.…”

Section: Resultsmentioning

confidence: 99%

Interaction of ambient nitrogen gas and laser ablated carbon plume: Formation of CN

Thareja

Dwivedi

Ebihara

2002

Nuclear Instruments and Methods in Physics Research Section B:

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Pulsed laser ablated carbon plasma in a nitrogen background gas in the pressure range from 10 mTorr to 100 Torr is investigated by optical emission spectroscopy using 1.064 and 0.355 lm laser wavelengths. C 2 and CN emission bands dominated the emitted spectrum at all ambient gas pressures at low incident laser intensity commonly used for pulsed laser deposition of thin films. The light intensity of C 2 and CN band heads is highly dependent on laser wavelength, laser energy, and ambient gas pressures. Emission from N þ 2 was detected at all nitrogen pressures. N I and N II are also observed in the emitted spectrum at the background gas pressure greater than 1 Torr. The vibrational temperature of CN species is found to be greater than that of C 2 species. The mechanism of formation of C 2 and CN molecules is discussed. Ó

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Section: Resultsmentioning

confidence: 99%

Interaction of ambient nitrogen gas and laser ablated carbon plume: Formation of CN

Thareja

Dwivedi

Ebihara

2002

Nuclear Instruments and Methods in Physics Research Section B:

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“…In these data, it is apparent that a relationship exists between the ionic emission spectra in the plumes under study and the degree of vibrational emission observed in the same plasma [35]. For the runs at 5¥10 The formation of dimers can happen by one of two situations: either the dimers are formed in the presence of ions in densities proportional to the ion density, or a similar density of ions to dimers leaves the target surface initially [36]. It is unlikely that a significant number of dimers is emitted from the target surface because the bond energy of Si 2 is only about 1 eV [37], as compared with the first ionization energy of atomic silicon of 8.1 eV.…”

Section: Figure 15mentioning

confidence: 97%

The effect of ionization on cluster formation in laser ablation plumes

Tillack

Blair²,

Harilal³

2004

Nanotechnology

118

104

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Ablation plumes caused by short-pulse laser irradiation provide conditions which are well suited to the formation of nanoclusters. The high saturation ratios and presence of ionization lead to extraordinarily high nucleation rates and small critical radii. We have explored the homogeneous nucleation and heterogeneous growth of condensate from Si targets expanding into a low-pressure He ambient using a Nd:YAG laser with pulse length of 8 ns, wavelength of 532 nm and intensities in the range of 5¥10 7 to 5¥10 9 W/cm 2 . Clusters in the range of 5-50 nm have been produced. In the highly dynamic, non-linear regime of short-pulse laser-matter interactions, plume evolution and condensation processes are strongly coupled and difficult to predict accurately from modeling alone. Both numerical predictions and experimental results were used to quantify the competing effects of ionization and supersaturation. The results suggest a dominant influence of ionization for nearly all intensities above the ablation threshold.

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“…Another result was the detection of C 2 molecular species in the nitrogen atmosphere, evidenced from characteristic emission lines belonging to the Swan A 3 Π g -X '3 Π u system. Detection of C 2 molecules is related to plume thermalization caused by collisions with background nitrogen molecules, promoting recombination of C to form C 2 [11]. Fullerenelike CNx films have predominantly graphite-like structures and require sp 2 electron hybridization.…”

Section: Resultsmentioning

confidence: 99%

Plasma characterization of pulsed-laser ablation process used for fullerene-like CNx thin film deposition

Riascos¹,

Zambrano²

2004

Braz. J. Phys.

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An in situ Optical Emission Spectroscopy (OES) characterization was performed on Pulsed-Laser Ablation (PLA) process used for fullerene-like CNx thin film deposition at nitrogen pressures within the 5 -100 mTorr range. Plumes were generated by ablation of pyrolytic graphite (99.99%) target using a (500 mJ, 7 ns, 1064 nm) Nd: YAG-pulsed laser. The spectra from the plume show, essentially, the presence of the band heads of CN Violet vibrational/rotational B 2 Σ + -X 2 Σ + system and the characteristic C 2 emission lines, belonging to the Swan A 3 Π g -X '3 Π u system. These excited CN and C 2 molecules were generated by laser ablation and by collisions of the plume with the substrate surface. Their vibrational temperatures were strongly dependent on nitrogen pressure during the deposition process and presented a decrease between 2.64 and 1.23 eV, as pressure increased from 5 to 100 mTorr. Synthesis of fullerene-like structures required high molecular temperatures at the condensation surface. High concentrations of CN radicals in the plasma promoted nitrogen incorporation into the films. The OES plasma characterization allowed for a correlation of the concentration and vibrational temperatures of CN and C2 species present in the plasma with the fullerene-like CNx film composition and bonding, determined by XPS, IR, and Raman spectroscopy.

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Temporal and spatial evolution of C2 in laser induced plasma from graphite target

Cited by 79 publications

References 38 publications

Interaction of ambient nitrogen gas and laser ablated carbon plume: Formation of CN

Interaction of ambient nitrogen gas and laser ablated carbon plume: Formation of CN

The effect of ionization on cluster formation in laser ablation plumes

Plasma characterization of pulsed-laser ablation process used for fullerene-like CNx thin film deposition

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