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Photoelectron angular distributions from ω-(n-pyrrolyl)alkanethiol self-assembled monolayers (SAMs) were calculated within a single-scattering approximation of the photoemission process. The calculations were carried out on two different... more
Photoelectron angular distributions from ω-(n-pyrrolyl)alkanethiol self-assembled monolayers (SAMs) were calculated within a single-scattering approximation of the photoemission process. The calculations were carried out on two different surface structures with face-stacked and herringbone arrangements of the pyrrole groups, which were deduced from molecular dynamics calculations. The characteristic angular patterns calculated for the molecular orbital originating from the pyrrole group involve information on the orientations of the pyrrole groups, which allows distinction between these arrangements. The photoelectron angular distributions from substituted SAMs can be used as a clue for studying the surface structures of the substituent groups.
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ABSTRACT Using Penning ionization electron spectroscopy, which provides information on the local distribution of the individual orbitals exposed outside the outermost surface layer, ultra-thin films (1 to several monolayers) of... more
ABSTRACT Using Penning ionization electron spectroscopy, which provides information on the local distribution of the individual orbitals exposed outside the outermost surface layer, ultra-thin films (1 to several monolayers) of chloroaluminium phthalocyanine were characterized during layer-by-layer vacuum deposition onto an MoS2 substrate and the change in the molecular orientation was sensitively detected.
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... In the MEEM, on the other hand, an image contrast was hardly detected since all of emitted electrons were used for the imaging. ... [8] Y. Harada, S. Yamamoto, M. Aoki, S. Masuda, N. Ueno,T. Ichinokawa, M. Kato and Y. Sakai, Nature... more
... In the MEEM, on the other hand, an image contrast was hardly detected since all of emitted electrons were used for the imaging. ... [8] Y. Harada, S. Yamamoto, M. Aoki, S. Masuda, N. Ueno,T. Ichinokawa, M. Kato and Y. Sakai, Nature (London) 372 (1994), p. 657. ...
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Research Interests: Condensed Matter Physics, Chemistry, Organic Semiconductors, PHOTOELECTRON SPECTROSCOPY, Semiconductor, and 10 moreUltraviolet, Thin Film, Electron, Organic Semiconductor, Electrical Properties, Charge Transport, Photoemission, Experimental Measurement, Intermolecular Interaction, and State observer
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Research Interests: Engineering, Materials Science, Electronics, Organic Semiconductors, Advanced Materials, and 14 moreOptoelectronics, Semiconductor, Physical sciences, Organic Semiconductor, Interfaces, Pentacene, CHEMICAL SCIENCES, Ionization, Ionization Potential, Work Function, Fermi Level, Monolayer, ionization energy, and Kelvin probe force microscope (KPFM)
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ABSTRACT
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ABSTRACTStructure-related ionization energy (IE) of vacuum-deposited titanyl-phthalocyanine (OTiPc) thin films was investigated by using in situ ultraviolet photoelectron spectroscopy (UPS) and X-ray diffractometry. Distinct molecular... more
ABSTRACTStructure-related ionization energy (IE) of vacuum-deposited titanyl-phthalocyanine (OTiPc) thin films was investigated by using in situ ultraviolet photoelectron spectroscopy (UPS) and X-ray diffractometry. Distinct molecular orientations (i.e. lying-flat and standing-up orientation) in different polymorphous (i.e. monoclinic β-phase and triclinic α-phase) were observed on a surface of polycrystalline (poly-) Au and octadecyltrichlorosilane-self assembled monolayer (OTS-SAM). For the two structures IE of the highest occupied molecular orbital (HOMO) of OTiPc thin films altered significantly by 0.55 eV. The different IE was attributed to surface dipole potential and strong intermolecular interaction.
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ABSTRACT Operation mechanisms and efficiencies of organic electronic devices are principally dominated by the electronic structures of organic semiconductor solids via charge carrier behaviors inside the active materials of the devices;... more
ABSTRACT Operation mechanisms and efficiencies of organic electronic devices are principally dominated by the electronic structures of organic semiconductor solids via charge carrier behaviors inside the active materials of the devices; that is the band dispersion for highmobility crystalline materials being desirable to e.g. organic field effect transistor application. Angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) is one of the most direct and sophisticated techniques to access the valence band of the matters. In this chapter, we describe technical essences of this methodology and introduce several examples of successful demonstrations of the valence band structures of crystalline organic semiconducting materials.
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10.1002/9783527653171.ch1The Molecule-Metal Interface1-1
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Abstract The electronic structure of oriented thin films of sexiphenyl (6P) as a short model compound of poly( p -phenylene) (PPP) was investigated by angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) using synchrotron... more
Abstract The electronic structure of oriented thin films of sexiphenyl (6P) as a short model compound of poly( p -phenylene) (PPP) was investigated by angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) using synchrotron radiation. The sample film of 6P was prepared by vacuum evaporation onto a heated Ag substrate. Infrared reflection-absorption spectroscopy, x-ray diffraction, and the observed selection rules for ARUPS indicated that the 6P molecules are highly oriented aligning its molecular axis parallel to the surface normal. In the normal emission spectra of ARUPS, the band intensity of the HOMO and the next HOMO was enhanced at hν =28∼40 eV . This enhancement can be explained in terms of the wave number( k )-conservation rule in the one-dimensional intramolecular band with some initial state broadening of k (or relaxation of k -conservation rule) due to the small number of repeating units. This indicates that wave number k along the molecular axis serves as a reasonably good quantum number even in a system consisting of only six repeating units.
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The molecular orientation at the surfaces of poly(9-vinylcarbazole) (PvCz) thin films was studied by angle-resolved ultraviolet photoelectron spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The observed... more
The molecular orientation at the surfaces of poly(9-vinylcarbazole) (PvCz) thin films was studied by angle-resolved ultraviolet photoelectron spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The observed take-off angle (θ) dependence of photoelectron intensities from top π band peaks clearly at larger θ than the calculated one for the three-dimensional isotropic random orientation model. The results indicate that there
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Dry-etching durabilities of poly(2-vinylnaphthalene-co-methyl methacrylate), the blend of poly(2-vinylnaphthalene) and poly(methyl methacrylate) [PMMA], and poly(α-methylstyrene-co-methyl methacrylate) films were studied as a function of... more
Dry-etching durabilities of poly(2-vinylnaphthalene-co-methyl methacrylate), the blend of poly(2-vinylnaphthalene) and poly(methyl methacrylate) [PMMA], and poly(α-methylstyrene-co-methyl methacrylate) films were studied as a function of vinylnaphthalene or α-methylstyrene content against four types of dry etching: 1) O2 plasma etching ( O2 PE), 2) O2 reactive ion etching ( O2 RIE), 3) Ar+ sputter etching (Ar SE), and 4) Ar ion beam etching (Ar IBE). Since the etching depth increased linearly with etching time the two-component polymer films were regarded to be etched uniformly without selected removal of aliphatic monomer units. Substantial enhacement of the durability was observed by incorporating or blending small amounts of aromatic moiety into PMMA for physical etching (Ar SE, Ar IBE) and physical/chemical etching ( O2 RIE) as well as chemical etching ( O2 PE). O2 RIE is a synergetic process involving both physical bombardment and chemical reaction.
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Electronic structure of perfluorotetracosane [n- CF 3 ( CF 2)22 CF 3; PFT], which is an oligomer of poly(tetrafluoroethylene) (PTFE), was investigated by angle-resolved photoemission spectroscopy (ARUPS) with synchrotron radiation.... more
Electronic structure of perfluorotetracosane [n- CF 3 ( CF 2)22 CF 3; PFT], which is an oligomer of poly(tetrafluoroethylene) (PTFE), was investigated by angle-resolved photoemission spectroscopy (ARUPS) with synchrotron radiation. Theoretical simulations of ARUPS spectra were also performed by the independent atomic center (IAC) approximation combined with ab initio molecular orbital (MO) calculations. Measured normal-emission spectra for end-on oriented (the long-chain axis of PFT is perpendicular to the surface) films showed an incident photon energy dependence due to the intramolecular energy band dispersion. The energy band structure along the long-chain direction of PFT obtained from measured and calculated spectra is also discussed.
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Research Interests: Materials Science, Others, Band Gap, Dipole, Work Function, and 3 moreFermi Level, Acceptor, and band bending
We have investigated the relation between the intramolecular vibrational modes of pentacene and the charge redistribution at the pentacene–graphite interface by using high-resolution electron-energy-loss-spectroscopy. The three main... more
We have investigated the relation between the intramolecular vibrational modes of pentacene and the charge redistribution at the pentacene–graphite interface by using high-resolution electron-energy-loss-spectroscopy. The three main vibrational peaks shift to lower energies as the pentacene film thickness decreases. In order to discuss this energy shift, we have calculated the vibrational energies of a free pentacene molecule by changing its charge state. We have also calculated the vibrational energies of a pentacene molecule adsorbed on a graphite sheet by changing the pentacene–graphite distance. Taking the experimental and calculation results into account, we conclude that the observed energy shifts result from an intramolecular charge redistribution. The present results indicate that the effect of an intramolecular charge redistribution is essential to discuss the origin of an energy shift observed in a vibrational study of an organic molecule/substrate interface.
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Abstract An efficient inverted polymer solar cell (PSC) is reported by integrating a small molecular electron collection layer (ECL) between indium tin oxide (ITO) cathode and the photoactive layer of blended poly(3-hexylthiophene) and... more
Abstract An efficient inverted polymer solar cell (PSC) is reported by integrating a small molecular electron collection layer (ECL) between indium tin oxide (ITO) cathode and the photoactive layer of blended poly(3-hexylthiophene) and [6,6]-phenyl C61 butyric acid methyl ester (P3HT:PCBM). The ECL is composed of a cesium carbonate-doped tris(8-hydroxyquinolinato) aluminum (Cs2CO3:Alq3) layer. As determined by photoelectron spectroscopy and electrical measurements, the Cs2CO3 doping induces suitable energy level alignment at the ITO/Cs2CO3:Alq3/PCBM interface and the increase in bulk conductivity of organic ECL, which are favorable to electron extraction through Cs2CO3:Alq3 to ITO cathode. In addition, optical simulation indicates that the Cs2CO3:Alq3 layer can act as an optical spacer to modulate the region of highest incident light intensity within the photoactive layer, where absorption and charge dissociation are efficient. The inverted PSC with an optimized Cs2CO3:Alq3 ECL exhibits a power conversion efficiency of 4.83%. The method reported here provides a facile approach to achieve high-performance inverted PSCs at low processing temperature.
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ABSTRACT We have studied the temperature-dependent electronic states of a copper-phthalocyanine (CuPc) monolayer film adsorbed on a graphite substrate by using metastable-atom electron spectroscopy and ultraviolet photoelectron... more
ABSTRACT We have studied the temperature-dependent electronic states of a copper-phthalocyanine (CuPc) monolayer film adsorbed on a graphite substrate by using metastable-atom electron spectroscopy and ultraviolet photoelectron spectroscopy. The CuPc molecules, which are flat-lying at room temperature, become tilted and condensed at temperatures below 130 K. Taking the temperature-dependent transition reported in the literature into account, we conclude that the transition observed in the present study originates from the change in the correlation between the molecule–substrate and the intermolecular interactions.
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Research Interests: Materials Science, Surfaces and Interfaces, Electron Transfer, Ultraviolet, Solid State electronic devices, and 15 morePhysical sciences, Pentacene, Double Layer, Photoemission Spectroscopy, Low energy electron diffraction, Electronic Structure, CHEMICAL SCIENCES, Schottky Barrier, Interface States, Work Function, Photoemission, Electronic band structure, Secondary Electron, Monolayer, and Organic Compound
Interpreting experimental spectra of thin films of organic semiconductors is challenging, and understanding the relationship between experimental data obtained by different spectroscopic techniques requires a careful consideration of the... more
Interpreting experimental spectra of thin films of organic semiconductors is challenging, and understanding the relationship between experimental data obtained by different spectroscopic techniques requires a careful consideration of the initial and final states for each process.