Core excitons at the boron<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>K</mml:mi></mml:math>edge in hexagonal BN

Davies, Brian M.; Bassani, F.; Brown, F. C.; Olson, C. G.

doi:10.1103/physrevb.24.3537

Cited by 52 publications

(26 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This identification of a Y 10 -type exciton is consistent with the fact that boron atoms sit only at sites with reflection symmetry about the a-b basal plane, which demands that each final state be an eigenstate of the corresponding reflection parity 22 . For a predominantly Y 10 -type exciton, other possible higher-order Y lm components must possess the same reflection parity.…”

supporting

confidence: 73%

“…The anisotropy of the dipole-limit core excitation spectra for q c and q ⊥ c for h-BN is well known from previous EELS 21 , XANES 22,23 , and XRS 24 studies at the q = 0 limit. We extend on this prior work by measuring the q-dependent boron XRS for both q c and q ⊥ c out to q = 9Å −1 , a momentum transfer that is clearly beyond the dipole limit for the B 1s initial state.…”

mentioning

confidence: 55%

“…Previous experimental studies have suggested that the physical origin of the pre-edge peak in h-BN is a core exciton 22,29 . Theoretical calculations have confirmed this notion by demonstrating the importance of the interaction between the core-hole and the photoelectron 30 .…”

mentioning

confidence: 99%

See 2 more Smart Citations

Exciton spectroscopy of hexagonal boron nitride using nonresonant x-ray Raman scattering

et al. 2008

View full text Add to dashboard Cite

We report non-resonant x-ray Raman scattering (XRS) measurements from hexagonal boron nitride for transferred momentum from 2 to 9Å −1 along directions both in and out of the basal plane. A symmetry-based argument, together with real-space full multiple scattering calculations of the projected density of states in the spherical harmonics basis, reveals that a strong pre-edge feature is a dominantly Y10-type Frenkel exciton with no other s-, p-, or d -components. This conclusion is supported by a second, independent calculation of the q-dependent XRS cross-section based on the Bethe-Salpeter equation. The physics of low-energy photoelectrons in solids is a complex, many body problem 1 . All aspects of the electronic structure of the material must be taken into account 2,3 , including the interaction between the photoelectron and the complementary hole 3,4,5,6 . This latter effect allows for similar long-lived bound states in metals (generally called Fermi-edge singularities) 7 and in insulators (called excitons) 8 . As a canonical example of a many body problem in condensed matter physics, core-excitons are a topic of continuing interest 4,5,6 .The present synergy between steadily progressing ab initio theoretical treatments 2,3,9,10 and on-going improvements in instrumentation 11 in studies of nonresonant x-ray Raman scattering (XRS) shows a strong potential for rapid progress on this old problem 5,6 . XRS is the inelastic scattering of hard x-rays from bound electrons, and XRS studies have seen a recent explosion in the number and range of applications 5,6,11,12,13,14,15,16,17 . In comparison with q-resolved electron energy loss spectroscopy (EELS) 18 , XRS is more suited for bulk condensed matter systems 13 due to the large penetration length afforded by the relative high-energy incident and scattered photons. The measured q-dependent XRS provides direct information about multipole contributions to the dynamic structure factor S(q, ω) 5,6,14,15,16 . It can be directly compared with theoretical calculations of S(q, ω) 6,14,15,16 , and can in some cases be inverted to provide an experimental measure of the perturbed projected density of states (l -DOS) 10,19 , which can again be compared to theory.XRS has shown itself to be especially suitable for spectroscopy of the angular characteristics of core excitons at the near edge region. For example, XRS studies 5,6 on LiF and icosahedral B 4 C convincingly demonstrated s-, and p-type excitons at the F and B K-edges, respectively, which can be attributed to atoms located at a center of inversion symmetry of the unit cell with parity a good quantum number for the final states 6 . Here, we demonstrate that for some systems one can learn not only the ∆l selection rule for the exciton but also a full description of its angular characteristics in terms of spherical harmonics, Y lm .We present measurements of the q-dependent XRS of hexagonal boron nitride (h-BN), an anisotropic system with all atoms sitting at positions with reflection symmetry to the basal plane (Figure 1,...

show abstract

supporting

confidence: 73%

mentioning

confidence: 55%

See 1 more Smart Citation

Exciton spectroscopy of hexagonal boron nitride using nonresonant x-ray Raman scattering

et al. 2008

View full text Add to dashboard Cite

show abstract

“…[5][6][7][8][9] Despite of many efforts in the past, the electronic properties of hBN remain largely unknown. They have been earlier studied by luminescence, 1,10-17 optical reflectance and absorption, [18][19][20][21] photoconductivity, 22 x-ray emission, [23][24][25] inelastic x-ray scattering, [26][27][28] x-ray absorption, 25,29,30 and electron energy loss [31][32][33] spectroscopy. After all, a large spread of band-gap energies reported in literature, ranging from 3.1 to 7.1 eV, 14 is currently explained by sample quality and related to experimental methods used.…”

Section: Introductionmentioning

confidence: 99%

Defect-related photoluminescence of hexagonal boron nitride

Museur

Feldbach²,

Kanaev³

2008

Phys. Rev. B

234

227

View full text Add to dashboard Cite

Photoluminescence of polycrystalline hexagonal boron nitride ͑hBN͒ was measured by means of time-and energy-resolved spectroscopy methods. The observed bands are related to donor-acceptor pair transitions, impurities, and structural defects. The excitation of samples by high-energy photons above 5.4 eV enables a phenomenon of photostimulated luminescence ͑PSL͒, which is due to distantly trapped conduction band electrons and valence band holes. These trapped charges are metastable and their re-excitation with low-energy photons results in anti-Stokes photoluminescence. The comparison of photoluminescence excitation spectra and PSL excitation spectra allows band analysis that supports the hypothesis of Frenkel-type exciton in hBN with a large binding energy.

show abstract

“…[8][9][10][11][12] However, the influence of the core hole on the spectral shape hampers a straightforward interpretation of the spectra, as was recognized already in the early works. 2,3,9,13 The near-edge absorption fine structure ͑NEXAFS͒ at the B 1s, C 1s, and N 1s thresholds in h-BN and graphite is affected differently by the corresponding core holes, due to the different core-hole screening. Therefore, a correct theoretical description of all XA spectra in h-BN and graphite is difficult from an initial or final-state approach, as well as from a transition state model, because the degree of screening is very different and unknown a priori.…”

mentioning

confidence: 99%

Dynamical effects in x-ray absorption spectra of graphene and monolayeredh-BN on Ni(111)

Rusz

Preobrajenski

et al. 2010

Phys. Rev. B

View full text Add to dashboard Cite

We present first-principles calculations of x-ray absorption spectra of graphene and hexagonal BN monolayer on the Ni͑111͒ substrate. Including dynamical core-hole screening effects according to the theory of Mahan-Nozières-de Dominics ͑MND͒ results in an overall good agreement with previously published experimental data and our new observations. This approach provides a unified first-principles description of the electronic structure and core excitations in the sp 2 -bonded materials on metal surfaces and a better insight into the dynamics of screening effects. We demonstrate in particular that the observed spectral features of graphene and hexagonal BN can be well reproduced with the MND theory, and that they are determined by a delicate balance between initial and final-state effects. X-ray absorption spectroscopy ͑XAS͒ plays an important role in revealing the electronic structure of the sp 2 -bonded layered materials such as graphite and hexagonal boron nitride ͑h-BN͒. The element and symmetry selectivity of XAS makes it a convenient tool for probing the B 2p, C 2p, and N 2p density of states ͑DOS͒ in h-BN ͑Refs. 1-7͒ and graphite. [8][9][10][11][12] However, the influence of the core hole on the spectral shape hampers a straightforward interpretation of the spectra, as was recognized already in the early works. 2,3,9,13 The near-edge absorption fine structure ͑NEXAFS͒ at the B 1s, C 1s, and N 1s thresholds in h-BN and graphite is affected differently by the corresponding core holes, due to the different core-hole screening. Therefore, a correct theoretical description of all XA spectra in h-BN and graphite is difficult from an initial or final-state approach, as well as from a transition state model, because the degree of screening is very different and unknown a priori. Moreover, it can be necessary to assume a co-existence of good and poor screening and to use different theory levels even for one and the same spectrum, e.g., C 1s NEXAFS in bulk graphite. 14 The problem of a unified theoretical description of the NEXAFS in graphite and h-BN is especially severe for the ‫ء‬ excitations due to the strong differences in their life time. As shown in Fig. 1, the full width at half maximum of the ‫ء‬ resonance ͑peak A͒ in bulk materials ͑black curves͒ varies from 0.3 eV for the B 1s −1 ‫ء‬ excitation to 1.1 eV for the C 1s −1 ‫ء‬ excitation and further to several eV for the N 1s −1 ‫ء‬ excitation. Since the symmetry of the potential for the core-excited electron is the same in all three cases, the strong variation in life time of the ‫ء‬ excitation is exclusively due to the variation in the electron density on the absorbing site resulting, in particular, in different screening behavior. The differences in the core-hole lifetime account for the different decay dynamics. The relative rate of the nonradiative participator Auger decay is about 30% for the B 1s −1 ‫ء‬ excitation in h-BN, 7 about 2% for the C 1s −1 ‫ء‬ excitation in graphite, 11 and below 0.5% for the N 1s −1 ‫ء‬ excitation in h-BN, 7 as determined by...

show abstract

Core excitons at the boronKedge in hexagonal BN

Cited by 52 publications

References 19 publications

Exciton spectroscopy of hexagonal boron nitride using nonresonant x-ray Raman scattering

Exciton spectroscopy of hexagonal boron nitride using nonresonant x-ray Raman scattering

Defect-related photoluminescence of hexagonal boron nitride

Dynamical effects in x-ray absorption spectra of graphene and monolayeredh-BN on Ni(111)

Contact Info

Product

Resources

About