Low-energy inverse photoemission spectroscopy using a high-resolution grating spectrometer in the near ultraviolet range

Yoshida, Hiroyuki

doi:10.1063/1.4822119

Cited by 24 publications

(13 citation statements)

References 38 publications

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“…There are many commercially available spectrometers in the visible and NUV range. We demonstrate that these instruments can be used for the analysis of photons in LEIPS measurement [55]. In Figure 4b, the LEIPS setup using a Czerny-Turner spectrometer is compared with the VUV-IPES apparatus using the spectrometer ( Figure 4c).…”

Section: Photon Detectormentioning

confidence: 97%

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Principle and application of low energy inverse photoemission spectroscopy: A new method for measuring unoccupied states of organic semiconductors

Yoshida

2015

Journal of Electron Spectroscopy and Related Phenomena

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Information about the unoccupied states is crucial to both fundamental and applied physics of organic semiconductors. However, there were no available experimental methods that meet the requirement of such research. In this review, we describe a new experimental method to examine the unoccupied states, called low-energy inverse photoemission spectroscopy (LEIPS). An electron having the kinetic energy lower than the damage threshold of organic molecules is introduced to a sample film, and an emitted photon in the near-ultraviolet range is detected with high resolution and sensitivity. Unlike the previous inverse photoemission spectroscopy, the sample damage is negligible and the overall resolution is a factor of two improved to 0.25 eV. Using LEIPS, electron affinity of organic semiconductor can be determined with the same precision as photoemission spectroscopy for ionization energy. The instruments including an electron source and photon detectors as well as application to organic semiconductors are presented. Keywords low-energy inverse photoemission spectroscopy; unoccupied state; electron affinity; organic semiconductor; © 2015. This manuscript version is made available under the Elsevier user license

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Section: Photon Detectormentioning

confidence: 97%

“…Since the energy spread of incident electron is about 0.23 eV, the overall resolutions are in excellent agreement with the prediction confirming the apparatus works correctly. [54] and b) a spectrometer with the Czerny-Turner configuration [55]. c) The earlier IPES apparatus using the spectrometer shown for comparison.…”

Section: Performance Of Leipsmentioning

confidence: 99%

Principle and application of low energy inverse photoemission spectroscopy: A new method for measuring unoccupied states of organic semiconductors

Yoshida

2015

Journal of Electron Spectroscopy and Related Phenomena

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“…These finite widths represent the small chance that electrons interacting with the medium, primarily through electron-hole pair creation and plasmonic interaction, will have energy within the final-state gap. Typically, this final-state effect in ARPES is not used to measure unoccupied states, which are instead mapped by inverse photoemission [8] or very-low-energy electron diffraction [5,[9][10][11][12].…”

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confidence: 99%

Resolving unoccupied electronic states with laser ARPES in bismuth-based cuprate superconductors

et al. 2015

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Angle-resolved photoemission spectroscopy (ARPES) is typically used to study only the occupied electronic band structure of a material. Here we use laser-based ARPES to observe a feature in bismuth-based superconductors that, in contrast, is related to the unoccupied states. Specifically, we observe a dispersive suppression of intensity cutting across the valence band, which, when compared with relativistic one-step calculations, can be traced to two final-state gaps in the bands 6 eV above the Fermi level. This finding opens up possibilities to bring the ultra-high momentum resolution of existing laser-ARPES instruments to the unoccupied electron states. For cases where the finalstate gap is not the object of study, we find that its effects can be made to vanish under certain experimental conditions.Angle-resolved photoemission spectroscopy (ARPES) is a powerful experimental probe that has been used extensively to image the occupied electronic states of materials in an energy-and momentum-resolved manner [1,2]. Since it is based on Einstein's photoelectric effect, it cannot directly probe a material's unoccupied electronic states, but it has nevertheless provided signatures of gaps in the unoccupied states [3][4][5][6]. According to the one-step model [7], some electrons, after absorbing photons, may have energies which lie between two unoccupied bands. We call the space between the unoccupied bands a finalstate gap, although this gap may be confined to a limited momentum range, and disperse within that range. The photoemission intensity of these electrons is suppressed, but not suppressed completely, due to the finite widths of the final states. These finite widths represent the small chance that electrons interacting with the medium, primarily through electron-hole pair creation and plasmonic interaction, will have energy within the final-state gap. Typically, this final-state effect in ARPES is not used to measure unoccupied states, which are instead mapped by inverse photoemission[8] or very-low-energy electron diffraction [5,[9][10][11][12].Here we show that laser-based ARPES [13][14][15], under certain conditions, can be used to map final-state gaps in the electronic states of a material. This method provides the following advantages with respect to standard synchrotron-based ARPES: (a) improved momentum resolution and greater bulk sensitivity, due to the lower photon energy range available in laser-ARPES (6-7 eV)[13], * alanzara@lbl.gov and (b) access to unoccupied electron states closer to the Fermi level.Data are shown for cuprate superconductors Bi 2 Sr 2 CaCu 2 O 8+δ (Bi2212) and Bi 2 Sr 2−x La x CuO 6 (La-Bi2201) along the Γ-Y direction of the Brillouin zone, using ∼6 eV laser ARPES. In these measurements, a final-state gap can be seen as a line of suppressed intensity that disperses in momentum.When the final-state gap crosses the photoemitted valence band, it creates a distortion 100-140 meV below the Fermi level, depending on the photon energy. A second distortion is seen at 20-50 meV, indicating...

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“…The MoO 3 showed a remarkably positive value of E F at 6.69 eV, which is more positive than the upper edge of the valence band of C 60 (6.4 eV), as determined by X-ray photoelectron spectroscopy [41,42]. The value of E F for non-doped C 60 (black line) is located at 4.6 eV, near the lower edge of the conduction band, suggesting that this film is n-type in nature.…”

Section: Pn-control Of Single C 60 Filmsmentioning

confidence: 97%

Bandgap Science for Organic Solar Cells

et al. 2014

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Abstract:The concept of bandgap science of organic semiconductor films for use in photovoltaic cells, namely, high-purification, pn-control by doping, and design of the built-in potential based on precisely-evaluated doping parameters, is summarized. The principle characteristics of organic solar cells, namely, the exciton, donor (D)/acceptor (A) sensitization, and p-i-n cells containing co-deposited and D/A molecular blended i-interlayers, are explained. 'Seven-nines' (7N) purification, together with phase-separation/cystallization induced by co-evaporant 3 rd molecules allowed us to fabricate 5.3% efficient cells based on 1 µm-thick fullerene:phthalocyanine (C 60 :H 2 Pc) co-deposited films.

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Low-energy inverse photoemission spectroscopy using a high-resolution grating spectrometer in the near ultraviolet range

Cited by 24 publications

References 38 publications

Principle and application of low energy inverse photoemission spectroscopy: A new method for measuring unoccupied states of organic semiconductors

Principle and application of low energy inverse photoemission spectroscopy: A new method for measuring unoccupied states of organic semiconductors

Resolving unoccupied electronic states with laser ARPES in bismuth-based cuprate superconductors

Bandgap Science for Organic Solar Cells

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