Conduction-band structure of graphite single crystals studied by angle-resolved inverse photoemission and target-current spectroscopy

Abstract.We have studied the chemisorption of atomic hydrogen on the basal plane of natural graphite single crystals. LEED and angle-resolved photoemission were used to characterize the clean surface. The adsorption of H saturates at rather low exposures, accompanied by a decrease of the work function by A~ = (100-4-20)meV. The photoemission spectra indicate a clear carbon-hydrogen interaction, leading to shifts of substrate bands by up to about 200meV. No detectable etching of the surface occurs at room temperature, in agreement with earlier work. Our results are qualitatively consistent with theoretical considerations about a strong H(ls)-C(2p~) chemical bond. 79.60.-i, 82.65.-i structure may then often produce a fingerprint of the Hsubstrate interaction in the photoelectron energy distribution curves. We will show below that, indeed, such effects can be clearly identified in spectra collected at high electron energy resolution. PACS:The electronic energy bands of the clean graphite substrate have been investigated experimentally by several groups. We list only the most recent investigations of the occupied [8,9] and empty [10-12] bands here. Earlier work is quoted extensively in these references. To summarize these results we note that the graphite band structure is known experimentally with sufficient reliability for the purpose of our investigation. The present paper reports on our photoemission results. In a subsequent paper [22] we will present a rather detailed study using thermal desorption spectroscopy.The interaction of atomic hydrogen with graphite surfaces has attracted considerable interest in the past. The main impetus to these investigations results from the importance of the hydrogen-wall interactions in plasma experiments. Several papers considered and reviewed particular aspects of the interaction between the plasma and the graphite surface, see, e.g., [1][2][3][4]. Another point of interest is the observation of synergistic effects due to multispecies impact, for example simultaneous interaction of atomic hydrogen and energetic ions [5,6]. In almost all investigations reported so far, other species besides atomic hydrogen were present. We therefore decided to study exclusively the action of hydrogen chemisorbed on a clean, well defined single-crystal surface of graphite by means of angle-resolved photoelectron spectroscopy and other surface-analytical techniques.It is well known from numerous adsorbate studies on metal surfaces that it is by no means trivial to detect photoemission out of orbitals of chemisorbed atomic hydrogen [7]. In general, small photoionization cross sections make such contributions very weak as compared to the substrate emission intensity. However, due to its small size the H atom can get very close to the surface. Therefore, it may introduce strong perturbations to several neighbouring substrate atoms, and the subsequent local change in the substrate electronic ExperimentalThe experiments were performed using a home-made highresolution simulated spherical sector anal...

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“…We always obtained • = (4.7 -t-0.1) eV, in excellent agreement with ~ = 4.7 eV [11,19] and with • = 4.6 eV [20].…”

Section: Resultssupporting

confidence: 73%

Interaction of atomic hydrogen with the graphite single-crystal surface

et al. 1992

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“…It should also be pointed out that identification of the fine structure in TCS (calculated curve 6 and experimental data [7] shown by curve 7) and LEET spectra through the negative second derivative Àd 2 IðE; XÞ=dE 2 is less efficient (see, e.g., Ref. [11]), because, in this case, the peaks shift markedly away from the band edges and a parasitic structure forms between them.…”

Section: Article In Pressmentioning

confidence: 99%

“…A theoretical analysis of the fine structure of these spectra turned out to be difficult because of the need to take into account the diverse physical processes occurring in the interaction of a flux of primary electrons I p with the near-surface region of a crystal. For instance, the positions of the maxima E i ¼ Àd 2 I=dE 2 in the TCS of single-crystal graphite obtained at various primary-electron incidence angles (wave vectors k) have been studied and the final conduction-band states E ¼ E i as a function of E(k) have been constructed [11]. In this case, however, information on E(k) can be distorted by the combined effect of the structure of various bands, which requires a more detailed theoretical consideration.…”

Section: Theoretical Modelmentioning

confidence: 99%

“…Low-energy electrons with kinetic energies E p below 1 keV are used to study the electronic structure of unoccupied high-level electronic states in very low-energy-electron diffraction (VLEED) [1,2], bremsstrahlung isochromat [3,4], inner-shell electron-energy loss [3,5], inverse photoemission (IPES) [3,6,7], secondary-electron emission [8,9], target current (TCS) [7,[10][11][12][13][14][15][16][17][18][19][20][21], and (as a modification of TCS) low-energy-electron transmission (LEET) [22][23][24][25][26] spectroscopies. Having a high surface sensitivity and being nondestructive, the latter two methods are employed, in addition to analyzing elementary excitations and near-surface Due to the specific features of their crystal and electronic structure, lamellar transition metal dichalcogenides (TMDC) feature a number of unique properties; as a result, the related materials do not have analogs and cannot be replaced by an equivalent counterpart.…”

Section: Introductionmentioning

confidence: 99%

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Low-energy absorbed current and electron transmission spectroscopies of molybdenum disulfide single crystal

Panchenko

2005

Physica B: Condensed Matter

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“…Low-energy electrons with kinetic energies E p below 1 keV are used to study the electronic structure of unoccupied high-level electronic states in very low-energy-electron diffraction (VLEED) [1][2][3], bremsstrahlung isochromat [4,5], inner-shell electron-energy loss [4,6], inverse photoemission (IPE) [4,7,8], secondary-electron emission [9,10], low-energy-electron transmission (LEET) [11][12][13][14][15], and absorbed (or target, total) current [8,[16][17][18][19][20][21][22][23][24][25][26][27] spectroscopies. Having a high surface sensitivity and being nondestructive, the latter two methods are employed, in addition to analyzing elementary excitations and near-surface states, in monitoring surface cleanness in the course of surface treatments, determination of the work function, etc.…”

Section: Introductionmentioning

confidence: 99%

Empty electronic states in low-energy absorbed current spectroscopy of NbSe2(0001) surface

Panchenko

2006

Surface Science

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Conduction-band structure of graphite single crystals studied by angle-resolved inverse photoemission and target-current spectroscopy

Cited by 49 publications

References 36 publications

Interaction of atomic hydrogen with the graphite single-crystal surface

Interaction of atomic hydrogen with the graphite single-crystal surface

Low-energy absorbed current and electron transmission spectroscopies of molybdenum disulfide single crystal

Empty electronic states in low-energy absorbed current spectroscopy of NbSe2(0001) surface

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