Experimental Investigation of the Band Structure of Graphite

Willis, R. F.; Feuerbacher, B.; Fitton, B.

doi:10.1103/physrevb.4.2441

Cited by 163 publications

(38 citation statements)

References 38 publications

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“…This minimum is indicated a t 272.8 eV in the XPS. From this follows for the experimentally definable energetic distance P; -P'; = 1.8 eV, compared with a theoretical value of 1.5 eV presented by Painter and Ellis [3], and which is in agreement whith the results given by Willis et al [15].…”

Section: Po-and S-electronssupporting

confidence: 79%

Combined Investigations of the Valence Band Structure of Graphite by K X‐Ray Emission Spectroscopy and X‐Ray Photoemission Spectroscopy

Berg

Dräger

Brümmer

1976

Physica Status Solidi (b)

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The structure of the valence band of graphite is investigated by combined application of X-ray photoelectron spectroscopy and a special X-ray emission spectroscopy which measures polarized radiation. The highly resolved K X-ray emission spectrum (XS) separated into 0-and x-bands by using their different polarisation and the X-ray photoemission spectrum (XPS) of this valence band are reported and discussed in connection with the calculated density of states. Width and overlapping range of the subbands are determined experimentally and compared with calculated values. The strong energy dependent differences between the intensities of the spectra and the density of states are interpreted by means of specific selection rules. The interpretations of the XPS are carried out with a cross section ratio a(2s)/a(2p) from 15 to 35. It is shown that the cross section of XPS for pcs-like electrons is higher than that for px-like electrons.Die Struktur des Valenzbandes von Graphit wird mit Hilfe kombinierter Anwendung derRontgenphotoelektronenspektroskopie und einer speziellenRontgenemissionsspektroskopie, welche polarisierte Strahlung mi& untersucht. Das hochaufgeloste Rontgen-KEmissionsspektrum (XS), welches in cs-und x-Banden getrennt ist, und das RontgenPhotoemissionsspektrum (XPS) dieses Valenzbandes werden mitgeteilt und im Zusammenhang mit der berechneten Zustandsdichte diskutiert. Breite und uberlappungsbereich der Subbanden werden experimentell bestimmt und mit berechneten Werten verglichen. Die stark energieabhangigen Unterschiede zwischen den Intensitaten der Spektren und der Zustandsdichte werden mit Hilfe von spezifischen Auswahlregeln interpretiert. Die Interpretationen der XPS werden mit einem Wirkungsquerschnittsverhaltnis ~(2s)/o(2p) zwischen 15 und 35 durchgefiihrt. Es wird gezeigt, daD der Wirkungsquerschnitt der Photoemissionsspektren fur pc-artige Elektronen groDer ist als jener fur px-artige Elektronen.

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Section: Po-and S-electronssupporting

confidence: 79%

Combined Investigations of the Valence Band Structure of Graphite by K X‐Ray Emission Spectroscopy and X‐Ray Photoemission Spectroscopy

Berg

Dräger

Brümmer

1976

Physica Status Solidi (b)

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“…The electronic structure of graphite has been studied extensively both experimentally and theoretically and is discussed elsewhere [14][15][16][17]. The He I spectrum shows a sharp peak at a binding energy of about 13.4eV which arises from photoelectrons scattered into unoccupied states [18].…”

Section: Resultsmentioning

confidence: 99%

Electron spectroscopy measurements on hydrogen implanted graphite and comparison to amorphous hydrogenated carbon films (a-C:H)

1992

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Abstract.Highly oriented pyrolytic graphite (HOPG) as well as polycrystalline graphite (pcgraphite) were bombarded with 3.5keV H + ions by means of a Penning ion source. The implanted graphite was characterized by in situ electron spectroscopy techniques such as UPS, XPS and EELS. Our UPS valence band measurements of the hydrogen saturated graphite reveal it to be an insulating phase, and XPS measurements show a shift of the Cls core level to higher binding energy with respect to pristine graphite. This behavior is explained by a Fermi energy shift upon hydrogen bombardment of graphite. In addition, a close resemblance in the electronic structure of hydrogen bombarded graphite and amorphous hydrogenated carbon films (a-C :H) is shown which suggests the modification of pristine graphite to an amorphous network [1] of mostly tetrahedrally bonded carbon atoms by hydrogen implantation. 79.20-m, 79.60-i, 73.60-n Graphite is an interesting material in the field of plasma fusion research because of its outstanding physical properties as a first wall material for limiters in fusion reactors (Tokamak) [2][3][4][5]. In particular, one requires a low-Zmaterial with a low vapor pressure. Graphite meets these specifications. PACS:During a tokamak discharge, the first wall interacts with the plasma and is bombarded by hydrogen species which leads to a considerable modification of the surface. Due to the immobility of the implanted hydrogen ions at room temperature, an upper limit of the hydrogen content nn/nc --0.45 is fou/ad in the near-surface region

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“…I n the case of graphite these transitions would be between critical points in the conduct'ion band, and as the coupling is essentially to the core hole excitation, the E 11 c and E 1 c preconditions for the incident electron would not have to be met. Uowever the data of Willis et al [13] does not afford an unequivocable assignment of the sharp satellites and, furthermore, a satellite corresponding to the strong E 1 c t'ransition a t 4.5 eV is absent. We would suggest, however, that coupling to interband transitions is responsible for the broad hump underlying the narrow loss peaks.…”

Section: The Aps Spectrum Of Pyrolitic Yruphitementioning

confidence: 91%

On the Soft X‐Ray Appearance Potential Spectrum of Graphite and Less Well‐ordered Carbons

Bradshaw

Menzel

1973

Physica Status Solidi (b)

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The technique of soft X-ray appearance potential spectroscopy (APS) has been applied to pyrolytic graphit>e and other carbons. The prominent, sharp satellites in the spectrum are assigned, in agreement with Houston and Park, to a coupling of the CK core hole excitation to strong plasmon emission (first and higher orders of the 7 eV plasmon and first order of the 27 eV plasmon). However, the peak separations of the higher order 7 eV plasmons are found to be not constant. The broad loss peaks are assigned to coupling with interband transitions. Increasing the degree of disorder of the carbon markedly affects the spectrum. The results are discussed in the light of more direct experimental investigations of electronic excitations in graphite, and of rrcent theoretical considerations of plasmon coupling in APS.Die Technik der Schwellenenergie-Spektroskopie (APS) weicher Rontgenstrahlung wurde auf Pyrographit und andere Kohlenstoffarten angewandt. I n ubereinstimmung mit, Houston und Park werden die gefundenen intensiven, schmalen Satelliten im Spektrum auf starlie Kopplung der ,,core hole"-Anregang mit Plasmonenemission (erste und hohere Ordnungen des 7 eV-Plasmons und erste Ordnung des 27 eV-Plasnions) zuruckgefuhrt. Die Abstande zwischen den hijheren Ordnungen des 7 eV-Plasmons sind jedoch nicht konstant. Die breiten Verluste werden durch Kopplung mit Interbandubergingen erklirt. Eine Erhohimg der Unordnung im Kohlenstoff verandert das Spektrum deutlich. Die Ergebnisse werden im Hinblick aiif die direkten experimentellen Untersuchungen von elektronischen Anregungen in Graphit und auf die jungsten theoretischen uberlegungen zur Plasmonenkopplung bei APS diskutiert. IntroduetionThe technique of appearance potential spectroscopy (APS) [ 1, 21 determines nondispersively the threshold pobential for the appearance of characteristic soft X-rays. Electrons are accelerated onto a solid sample giving rise to Bremsst>rahlung and characteristic lines. If the energy of the incident electrons is scanned, a sharp step is expected in the total X-ray yield a t an energy just large enough to excite a core electron to the Fermi level. The APS features are extracted as peaks using electronic differentiation. Recent interest has focussed on the form and intensity of APS features, because of their dependence on the density of empty conduction band states above the Fermi level. Houston and Park [3] point out that the densities of final states must take into account both the excited core electron and the scattered incident electron. The transition probability then becomes proportional to the product of the density of states a t the core level and the self-convolution of the density of empty states above the Fermi level [4]. This leads to an unsymmetrical peak rather than a simple step in the total X-ray yield, and a negative peak in the first derivative. I n addition Langreth and others [5] predict that t>he non-conservation of "slow charge" associated with production of the core hole will produce strong plasmon effects.

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Experimental Investigation of the Band Structure of Graphite

Cited by 163 publications

References 38 publications

Combined Investigations of the Valence Band Structure of Graphite by K X‐Ray Emission Spectroscopy and X‐Ray Photoemission Spectroscopy

Combined Investigations of the Valence Band Structure of Graphite by K X‐Ray Emission Spectroscopy and X‐Ray Photoemission Spectroscopy

Electron spectroscopy measurements on hydrogen implanted graphite and comparison to amorphous hydrogenated carbon films (a-C:H)

On the Soft X‐Ray Appearance Potential Spectrum of Graphite and Less Well‐ordered Carbons

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