Topic
Photoemission spectroscopy
About: Photoemission spectroscopy is a research topic. Over the lifetime, 10821 publications have been published within this topic receiving 250888 citations. The topic is also known as: photoelectron spectroscopy & PES.
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TL;DR: In this paper, the core-level and valence-level photoemission spectra, as well as the work function and energy-level alignment with a common hole-injection material, have been measured using X-ray and ultraviolet spectroscopy.
Abstract: We have investigated NiO thin films prepared by in situ and ex situ ozone oxidation, as well as air-exposed and vacuum-annealed NiO films. The core-level and valence-level photoemission spectra, as well as the work function and energy-level alignment with a common hole-injection material, have been measured using X-ray photoemission spectroscopy and ultraviolet photoemission spectroscopy. We found that in situ oxidation results in the formation of a purely NiO film, while ex situ oxidation and air exposure result in a hydroxide-terminated NiO film. Work functions as high as 6.7 eV can be achieved for in situ-oxidized NiO; however, the work function decreases rapidly with time due to adsorption of residual gases in vacuum. The work functions of ex situ and air-exposed NiO were significantly lower, between 5.2 and 5.6 eV, due to hydroxylation of the oxide surface. We have examined the rate at which the work function decreases with air exposure and found there to be a very rapid initial decrease in work func...
153 citations
TL;DR: It is demonstrated that the direct optical gap of single crystals is dominated by a strongly bound exciton rising over the continuum of indirect interband transitions, revealing the existence of strongly boundexcitons in single crystals and nanoparticles.
Abstract: Anatase TiO2 is among the most studied materials for light-energy conversion applications, but the nature of its fundamental charge excitations is still unknown. Yet it is crucial to establish whether light absorption creates uncorrelated electron-hole pairs or bound excitons and, in the latter case, to determine their character. Here, by combining steady-state angle-resolved photoemission spectroscopy and spectroscopic ellipsometry with state-of-the-art ab initio calculations, we demonstrate that the direct optical gap of single crystals is dominated by a strongly bound exciton rising over the continuum of indirect interband transitions. This exciton possesses an intermediate character between the Wannier-Mott and Frenkel regimes and displays a peculiar two-dimensional wavefunction in the three-dimensional lattice. The nature of the higher-energy excitations is also identified. The universal validity of our results is confirmed up to room temperature by observing the same elementary excitations in defect-rich samples (doped single crystals and nanoparticles) via ultrafast two-dimensional deep-ultraviolet spectroscopy.Here the authors combine steady-state angle-resolved photoemission spectroscopy, ellipsometry and ultrafast two-dimensional ultraviolet spectroscopy to examine the role of many-body correlations in anatase TiO2, revealing the existence of strongly bound excitons in single crystals and nanoparticles.
152 citations
TL;DR: The observed spectral behavior indicates that the observed MIT is caused by the reduction in the bandwidth due to the dimensional crossover, which is indicative of the MIT in a SrVO(3) ultrathin film.
Abstract: We have investigated the changes occurring in the electronic structure of digitally controlled SrVO(3) ultrathin films across the metal-insulator transition (MIT) by the film thickness using in situ photoemission spectroscopy. With decreasing film thickness, a pseudogap is formed at E(F) through spectral weight transfer from the coherent part to the incoherent part. The pseudogap finally evolves into an energy gap that is indicative of the MIT in a SrVO(3) ultrathin film. The observed spectral behavior is reproduced by layer dynamical-mean-field-theory calculations, and it indicates that the observed MIT is caused by the reduction in the bandwidth due to the dimensional crossover.
152 citations
TL;DR: Orientation-dependent ionization potentials of organic thin films have been investigated with the combination of synchrotron-based high-resolution photoemission spectroscopy and near-edge X-ray absorption fine structure measurements.
Abstract: Orientation-dependent ionization potentials (IPs) of organic thin films have been investigated with the combination of synchrotron-based high-resolution photoemission spectroscopy and near-edge X-ray absorption fine structure measurements Organic thin films of copper(II) phthalocyanine (CuPc) and its fully fluorinated counterpart of copper hexadecafluorophthalocyanine (F16CuPc) with well-controlled orientation are used as model systems Both molecules lie flat on the graphite surface and stand upright on Au(111) terminated by self-assembled monolayer of octane-1-thiol The IP for the standing-up CuPc thin film (IP = 475 eV) is 040 eV lower than that of the lying-down film (IP = 515 eV) In contrast, the IP of the standing up F16CuPc (IP = 650 eV) is 085 eV higher than that of the lying-down film (IP = 565 eV) This reversed orientation dependence in IP is explained by the opposite surface dipoles in the standing-up CuPc and F16CuPc molecular layers originating from the different intramolecular dipo
151 citations
TL;DR: In this article, the photoelectron spectra of clusters of I− solvated in water up to fifteen water molecules were measured and it was shown that the vertical binding energy of the electron increases with cluster size and levels off in clusters containing more than six water molecules.
Abstract: We have measured the photoelectron spectra of clusters of I‐ solvated in water up to fifteen water molecules. The vertical binding energy of the electron increases with cluster size and levels off in clusters containing more than six water molecules. These results strongly indicate that the first solvation layer around the ion consists of six water molecules. This picture is quantitatively consistent with the photoelectron spectroscopy result of I‐ solvated in bulk water.
151 citations