Raman spectra of diamondlike amorphous carbon films

Yoshikawa, Masanobu; Katagiri, Gen; Ishida, Hideyuki; Ishitani, A.; Akamatsu, Tomonari

doi:10.1063/1.342063

Cited by 250 publications

(67 citation statements)

References 17 publications

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“…8,9 The intensity ratio of the two bands, I D /I G , is inversely proportional to the crystallite size, where the intensity of D and G bands are defined as I D and I G , respectively. 10 An increase of I D /I G is corresponding to an increase of the edges of graphite crystallites or the boundaries of the larger crystallites. Raman spectrometry was also used to monitor the surface changes.…”

Section: Resultsmentioning

confidence: 99%

Atomization Mechanisms of Gold from Thermally Decomposed and Crudely Roughened Pyrolytically Coated Graphite Furnaces Using Electrothermal Atomization

et al. 1998

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Studies of atomization mechanism of gold and silver in electrothermal atomization seek a better understanding of the atomic vapor formation process and the type of interactions taking place between the analyte and the surface of the atomizer. This type of information can lead to logical approaches for improvement of the technique or the method of analysis. Arthur and Cho 1 reported the adsorption and desorption kinetics of gold on a single graphite crystal where adsorbed atoms (adatoms) can move on the single-crystal graphite and form droplets or caps. Scanning tunneling microscopy supported the existence of adatoms, microdroplets and two-dimensional islands on graphite for several atoms including gold.2 In an electrothermal graphite furnace atomic absorption spectrometry, it has been reported by using kinetic analysis that the desorption of gold occurs from microdroplets as a solution deposition is used. [3][4][5][6] Fonseca and co-workers 7 reported that vaporization of gold and silver appears to occur from varying sizes of microdroplets or from adatoms, depending on the analytical conditions, such as dry and thermal pretreatment conditions, chemisorbed oxygen on the graphite surface and mechanically created active sites on the graphite surface. In the case of silver, although a tendency of the activation energy (E a ) for atomization to increase as the concentration increases was observed with a fractional order desorption, a constant E a was observed below 0.06 ng of silver, which is in agreement with the morphology of dispersed atoms with a first order desorption. Unlike silver, gold did not approach a constant E a at low absorbances. They suggested that confirmation of a constant E a corresponding to the morphology of dispersed gold atoms would require a more sensitive technique or different atomizer design.The graphite surface consists of crystallites of graphite with carbons lying in a basal plane which is terminated by carbons in zigzag and armchair configurations. The edge and terminated carbons have unpaired s electrons which constitute active sites and exist at lattice defects and at boundaries of graphite crystallites. The active surface area of graphite normally accounts for only a few percent of total surface area, depending on the conditions of the surface. The number of active site is increased by thermal treatment and mechanically roughening of the graphite surface. On the graphite surface rich in the active sites, the easy formation of a highly dispersed state of gold (i.e. adatoms) can be expected. It was found that a constant E a was observed at low concentrations by using thermally decomposed and crudely roughened PG furnaces, corresponding to the morphology of highly dispersed atoms of gold (i.e. individual adatoms). ExperimentalA Hitachi Model Z-8000 flame and graphite furnace atomic absorption spectrometer equipped with a Zeeman effect background corrector, an optical temperature controller system (Hitachi Model 180-0341) and an automatic data processor were used. Twenty microliters of a...

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Section: Resultsmentioning

confidence: 99%

Atomization Mechanisms of Gold from Thermally Decomposed and Crudely Roughened Pyrolytically Coated Graphite Furnaces Using Electrothermal Atomization

et al. 1998

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“…2(c). The spectrum looks similar to amorphous carbon [28,29] and does not seem to correspond to the TEM images (Figs. 2(a) and (b)).…”

Section: Resultsmentioning

confidence: 84%

Molar Concentration Dependence of Sucrose Solution in Carbon Nanotube Synthesis by Liquid-Phase Arc Discharge

Aikawa

Kizu

Kamei

et al. 2011

e-J. Surf. Sci. Nanotechnol.

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We synthesized carbon nanotubes (CNTs) from sucrose solution, used as a carbon source, by the liquid-phase arc discharge method, which generates electric sparks between metal electrodes. The quality of the CNTs depends on the molar concentration of sucrose solution because the discharge characteristics vary with its viscosity. When a lower density solution, 0.5 mol/L in this study, was used, the G/D ratio of the generated CNTs was the highest. This result implies that discharge characteristics dependent on solution density play an important role in CNT synthesis in liquid-phase arc discharge. We also examined other saccharides (fructose, glucose, lactose, and maltose) as carbon sources. The results indicated that only sucrose molecules provide CNT precursors.

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“…16 The intensities of the Raman bands for the E2g and disorder modes are defined as IE2g and ID, respectively. The intensity ratio of the peaks, ID/IE2g, is inversely proportional to the crystallite size; 17 that is, the greater ID/IE2g indicates a graphite surface rich in edge carbon species corresponding to the active site. The ID/IE2g value also corresponds to the ratio of the crystallite surface area.…”

Section: Resultsmentioning

confidence: 99%

Desorption Mechanism of Arsenic from Non-Pyrolytic Graphite, Pyrolytic Graphite and Pyrolyzed Ascorbic Acid in Electrothermal Atomic Absorption Spectrometry

et al. 2000

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Investigating the atomization mechanisms in an electrothermal atomizer and vaporizer is important to improve the detection limit, sensitivity, and accuracy in various atomic spectrometries. Electrothermal atomic absorption spectrometry (ETAAS) is a highly sensitive analytical technique that extensively used in the direct determination of numerous elements because of its versality, speed, and specificity. Substantial losses of As due to the vaporization loss of gaseous oxides and As dimers have been reported, particularly when using a pyrolytically coated graphite (PG) furnace.McAllister reported that As4O6(g) is likely to be lost from the graphite furnace during prolonged drying of As samples at relatively low temperatures. 1The As2O3(s) is reduced with carbon:The reaction is endthermic and is carried out at 500 -800˚C. 2 Robinson et al. reported that the formation of gaseous As2 and As4 accounted for some of the analyte loss associated with molecular absorption in radiofrequency carbon atomization cells.3 Koreckova et al. observed absorption bands for As2(g) when samples were introduced on a tungsten wire into a hot graphite furnace, but did not observe the bands when As was introduced on graphite species. 4 Slaverykova and Tsalev carried out a kinetic investigation for analyte losses, such as As, Pb, Sb, and Sn, during a pre-atomization thermal treatment in the range 673 -1073 K. 5 The hold time for the pretreatment was varied between 5 -60 s at different fixed pretreatment temperatures. From the slopes of the linear regression plots, ln A/A0 versus t, the rate constants for the analyte loss process were evaluated. From the slopes of the Arrhenius plots, the apparent activation energies of the analyte loss process were derives. The apparent activation energies (Eas) were evaluated only for the initial stage of the loss process (<40 s). These values were 12±2, 16±2, 58±5, and 175±13 kJ mol -1 , observed for As, Pb, Sb, and Sn, respectively, being ranged in the approximate order of decreasing volatility of the analyte.It is proposed with mass and atomic absorption spectrometry by Styris et al. that As2O3 thermally decomposes, forming As monoxide, higher As oxides, and condensed phase As, which polymerizes and then sublimates as the dimer. 6 Atomization occurs by dissociative adsorption of the oxide and desorption of the resulting As. The following mechanisms were proposed:(1) It was found that Arrhenius plots were composed of two straight portions for As deposited on the PG and NPG furnace walls and of one straight portion for that on active carbon formed from the pyrolysis of ascorbic acid at a low-temperature pyrolysis. To correct the absorbance of the first peak for that of the second peak, the absorbance corresponding to the second peak in the period of the first peak was evaluated by extrapolating the straight line for the second peak to each atomization time. The activation energy (Ea) for the first peak depended on the ratio of the edge carbon species in graphite as the condensed phase based on Raman spec...

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Raman spectra of diamondlike amorphous carbon films

Cited by 250 publications

References 17 publications

Atomization Mechanisms of Gold from Thermally Decomposed and Crudely Roughened Pyrolytically Coated Graphite Furnaces Using Electrothermal Atomization

Atomization Mechanisms of Gold from Thermally Decomposed and Crudely Roughened Pyrolytically Coated Graphite Furnaces Using Electrothermal Atomization

Molar Concentration Dependence of Sucrose Solution in Carbon Nanotube Synthesis by Liquid-Phase Arc Discharge

Desorption Mechanism of Arsenic from Non-Pyrolytic Graphite, Pyrolytic Graphite and Pyrolyzed Ascorbic Acid in Electrothermal Atomic Absorption Spectrometry

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