巨大分子吸着系における価電子帯ホール・振動結合:有機電荷輸送機構の解明

• Project/Area Number: 17685019
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Single-year Grants
• Research Field: Functional materials/Devices
• Research Institution: Chiba University
• Principal Investigator: 解良 聡 Chiba University, 大学院・融合科学研究科, 准教授 (10334202)
• Project Period (FY): 2005 – 2007
• Project Status: Completed (Fiscal Year 2007)
• Budget Amount: ¥29,640,000 (Direct Cost: ¥22,800,000、Indirect Cost: ¥6,840,000); Fiscal Year 2007: ¥4,810,000 (Direct Cost: ¥3,700,000、Indirect Cost: ¥1,110,000); Fiscal Year 2006: ¥5,070,000 (Direct Cost: ¥3,900,000、Indirect Cost: ¥1,170,000); Fiscal Year 2005: ¥19,760,000 (Direct Cost: ¥15,200,000、Indirect Cost: ¥4,560,000)
• Keywords: 表面界面物性 / 有機半導体 / 電子分光 / 薄膜 / 分子配向 / 有機デバイス

Research Abstract

本研究では有機半導体薄膜特有の電子構造について「分子振動」というキーワードを掲げて研究を行った。弱い相互作用で結ばれた分子性固体中の電荷の動きを如何にして捉えるか、電子論物理的に記述できるかが命題である。光電子分光法という古来の手法を高精度測定を通じて有機半導体の系に斬新に活用することにより、ホッピング伝導の重要な要素である再配向エネルギーとトランスファー積分の両者に直接的に踏み込むことができた。ここで見出された、グラファイト基板上に分子を真空蒸着する手法により、これまで埋もれていた微細情報をあらわにすることに成功し、有機半導体の移動度の「第一原理測定」法としてのノウハウを蓄積した。
一例として、n型半導体として知られるフッ素化ペンタセン分子の吸着膜を作製したところ、二分子層において特徴的な二量体構造を形成することを見出した。高分解能光電子分光測定の結果、単量体と二量体の電子構造の変化は劇的であり、エネルギー準位分裂によるトランスファー積分と、二量体化による再配向エネルギーの減少を直接捉えることに成功した。つまり分子性固体のような弱い相互作用(ファンデアワールスカ)により支配される系において、明らかに分子間相互作用によるエネルギー変化が生じており、その軌道間の相互作用は従来考えられてきた値よりも遙かに大きいことを示すことに成功した(投稿準備中)。二量体における分裂測定は、バルク(結晶)においてエネルギーバンド分散が形成される過程の最も初期段階の電子構造を捉えたことになり、孤立分子系からの一連の弱い相互作用系の電子論が議論可能となったと言える。本課題を通じて得られた結果に関してレビュー誌を2報投稿中である。
有機電荷輸送機構の全容解明には至っていないが、多くの周辺物理も同時に見出されており、分子性固体における基盤学理構築へ向けて確実に前進したといるといえる。

Research Products

• [Journal Article] A multi-technique investigation of TiO_2 films prepared by magnetron sputtering (2008)
  • Author(s): M.B. Casu, et. al.
  • Journal Title: Surface Science 602 Pages: 1599-1606
  • Peer Reviewed
• [Journal Article] Chage in molecular conformation of dibenzo-crown ether induced by weak molecular-substrate interaction (2008)
  • Author(s): T. Hosokai, et. al.
  • Journal Title: Journal of Physical Chemistry C 112 Pages: 4643-4648
  • Peer Reviewed
• [Journal Article] Role of intrinsic band-gap states for the energy level alignment at weakly interacting organic-conductor interfaces: Gap states versus band dispersion in pentacene thin films (2007)
  • Author(s): N.Ueno, et. al.
  • Journal Title: SPIE Proceedings 6656
  • Peer Reviewed
• [Journal Article] Investigation of polarization effects in organic thin films by surface core-level shifts (2007)
  • Author(s): M.B. Casu, et. al.
  • Journal Title: Physical Review B 76
  • Peer Reviewed
• [Journal Article] Photoemission microspectroscopy and imaging of bilayer islands formed in monolayer titanyl phthalocyanine films (2007)
  • Author(s): T. Sugiyama, et. al.
  • Journal Title: Chemical Physics Letters 449 Pages: 319-322
  • Peer Reviewed
• [Journal Article] Substrate dependent molecular orientation in thin films of bisazomethinedye studied by metastable atom electron spectroscopy and ultraviolet photoelectron spectroscopy (2007)
  • Author(s): T. Hosokai, et. al.
  • Journal Title: Molecular Crystal and Liquid Crystal 472 Pages: 43-50
  • Peer Reviewed
• [Journal Article] The Control of Electronic States Spreading Outside the Conjugated Polymer Surface in Organic Electronics Materials, Devices and Applications (2007)
  • Author(s): X.T. Hao, et. al.
  • Journal Title: MRS Symposium Proceedings 965E
  • Peer Reviewed
• [Journal Article] Multiple Scattering Approach to Polarization Dependence of F K-Edge XANES Spectra for Highly Oriented Polytetrafluoroethylene (PTFE) Thin Film (2007)
  • Author(s): S. Nagamatsu, et. al.
  • Journal Title: AIP Conference Proceedings 882 Pages: 514-516
  • Peer Reviewed
• [Journal Article] Influence of intramolecular vibrations in charge redistribution at the pentacene-graphite interface (2007)
  • Author(s): K. Fujii, et. al.
  • Journal Title: Surface Science 601 Pages: 3765-3768
  • Peer Reviewed
• [Journal Article] Control of the Interchain π-π Interaction and Electron Density Distribution at the Surface of Conjugated Poly (3-hexylthiophe) Thin Films (2007)
  • Author(s): X.T. Hao, et. al.
  • Journal Title: Journal of Physical Chemistry B 111 Pages: 10365-10372
  • Peer Reviewed
• [Journal Article] Preparation Conditions of Pentacene Mnonolayer on Graphite Surface Studied by Photoemisson Electron Microscopy (2007)
  • Author(s): M. Shionoiri, et. al.
  • Journal Title: Japanese Journal of Applied Physics 46 Pages: 1625-1629
  • Peer Reviewed
• [Journal Article] Angle-resolved UV photoelectron spectroscopy of titanyl phthalocyanine monolayer film on graphite (2007)
  • Author(s): S. Kera, et. al.
  • Journal Title: Journal of ElectronSpectroscopy and Related Phenomena 156-158 Pages: 135-138
  • Peer Reviewed
• [Journal Article] Photoelectron Angular Distribution of 3d-orbital Dereived Bands in Mn-Phthalocyanine Monolayer (2007)
  • Author(s): S. Kera, et. al.
  • Journal Title: UVSOR Activity Report 2006 Pages: 115-115
• [Journal Article] Spectroscopic evidence of strong pi-pi interorbital interaction in a lead-phthalocyanine bilayer film attributed to the dimer nanostructure (2007)
  • Author(s): S.Kera et al.
  • Journal Title: Physical Review B (Rapid Communication) 75 Pages: 121305-4
• [Journal Article] The Role of Ionization Potential in Vacuum-level Alignment at Organic Semiconductor Interfaces (2007)
  • Author(s): H.Fukagawa et al.
  • Journal Title: Advanced Materials 19 (5) Pages: 665-668
• [Journal Article] Surface photodegradation of poly (vinylidene fluoride) by inner-shell excitation (2006)
  • Author(s): K.K.Okudaira et al.
  • Journal Title: Surface Review and Letters 13 Pages: 259-263
• [Journal Article] Ion desorption by inner-shell excitation and photodegradation of poly (vinylidene fluoride) (2006)
  • Author(s): K.K.Okudaira et al.
  • Journal Title: Materials Research Society Symposium Proceedings 887 Pages: 243-248
• [Journal Article] VUV induced doping of Cu-phthalocyanine thin films : A possibility of n-type doping (2006)
  • Author(s): M.Ono et al.
  • Journal Title: Molecular Crystals and Liquid Crystals 455 Pages: 251-256
• [Journal Article] Hole-Vibration Coupling in the Uppermost Valence Band Photoemission of Pentacene Monolayer on Graphite (2006)
  • Author(s): H.Yamane et al.
  • Journal Title: Molecular Crystals and Liquid Crystals 455 Pages: 235-240
• [Journal Article] Intermolecular and inter-layer interactions in copper phthalocyanine films as measured with microspot photoemission spectroscopy (2006)
  • Author(s): T.Sugiyama et al.
  • Journal Title: Applied Physics Letters 89 Pages: 202116-3
• [Journal Article] The Role of Ionization Potential in Vacuum-level Alignment at Organic Semiconductor Interfaces (2006)
  • Author(s): X.T.Hao et al.
  • Journal Title: Applied Physics Letters 89 Pages: 182113-3
• [Journal Article] Radiation damage to alkyl chain monolayers on semiconductor substrates investigated by electron spectroscopy (2006)
  • Author(s): F.Amy et al.
  • Journal Title: Journal of Physical Chemistry 110(43) Pages: 21826-21832
• [Journal Article] High-resolution inner-shell excitation spectroscopy of H2-phthalocyanine (2006)
  • Author(s): S.Kera et al.
  • Journal Title: The Journal of Chemical Physics 125 Pages: 14705-14708
• [Journal Article] Origin of Highest Occupied Band Position and Width of Pentacene Films : Hole Stabilization vs. Band Dispersion (2006)
  • Author(s): H.Fukagawa et al.
  • Journal Title: Physical Review B 73 Pages: 245310-5
• [Journal Article] Quantitative analysis of photoelectron angular distribution of single-domain organic monolayer film : NTCDA on GeS(001) (2006)
  • Author(s): S.Kera et al.
  • Journal Title: Chemicai Physics (In press)
• [Journal Article] Does the molecular orientation induce an electric dipole in Cu-phthalocyaninethin films? (2006)
  • Author(s): H.Yamane et al.
  • Journal Title: J. Applied Physics (In press)
• [Journal Article] Growth mode and molecular orientation of phthalocyanine molecules on metal single crystal substrates : a NEXAFS and XPS study (2006)
  • Author(s): S.Kera et al.
  • Journal Title: Surface Science 600 Pages: 1077-1077
• [Journal Article] Experimental Estimation of Molecular Dipole Moment and Polarizability of Titanyl Phthalocyanine Using Ultraviolet Photoelectron Spectroscopy (2006)
  • Author(s): H.Fukagawa et al.
  • Journal Title: Physical Review B (Rapid) 73 Pages: 41304-41304
• [Journal Article] UPS fine structures of highest occupied band in vanadyl-phthalocyanine ultrathin film (2005)
  • Author(s): H.Fukagawa et al.
  • Journal Title: J.Electron Spectroscopy Related Phenomena 144-147 Pages: 475-475
• [Journal Article] Hole-vibration coupling of the highest occupied state in pentacene thin films (2005)
  • Author(s): H.Yamane et al.
  • Journal Title: Physical Review B 72 Pages: 153412-153412
• [Journal Article] Fine structure of the highest occupied band in OTi-phthalocyanine monolayer (2005)
  • Author(s): H.Yamane et al.
  • Journal Title: Synthetic Metals 152 Pages: 297-297
• [Journal Article] Multiple-Scattering Approach, to Angle-Resolved Ultraviolet Photoelectron Spectroscopy of Large Molecules (2005)
  • Author(s): S.Nagamatsu et al.
  • Journal Title: e-J.Surf.Sci. Nanotech 3 Pages: 461-461
• [Journal Article] Direct Observation of the HOMO-hole/Vbration Coupling in Pentacene Thin Films by means of High-Resolution Ultraviolet Photoelectron Spectroscopy (2005)
  • Author(s): H.Yamane et al.
  • Journal Title: IPAP Conference Series 6 Pages: 19-19
• [Journal Article] Possibility of the Fermi Level Control by VUV-Induced Doping of an Organic Thin Film : Polytetrafluoroethylene (2005)
  • Author(s): M.Ono et al.
  • Journal Title: IPAP Conference Series 6 Pages: 27-27
• [Journal Article] Effects of the Dipole Density on the Electronic Structures of Oriented Thin Films of the Polarized Organic Molecule (2005)
  • Author(s): H.Fukagawa et al.
  • Journal Title: IPAP Conference Series 6 Pages: 73-73
• [Journal Article] Deep Insight into a Valence Hole in Organic Semiconductors : High-Resolution Ultraviolet Photoemission Spectroscopy (2005)
  • Author(s): S.Kera et al.
  • Journal Title: IPAP Conference Series 6 Pages: 51-51
• [Presentation] Hopping mobility of perfluoropentacene films measured with high-resolution UPS: Impacts of intermolecular interaction on the hole-vibration coupling (2007)
  • Author(s): S. Kera, et. al.
  • Organizer: Materials Research Society fall meeting 2007
  • Place of Presentation: Boston (USA)
  • Year and Date: 2007-11-26
• [Presentation] Work-Function-Dependent Hole Injection Barrier at Organic/Metal Interface: The Role of Band Tailing in Pentacene Aggregates (2007)
  • Author(s): S. Kera, et. al.
  • Organizer: The 4th Workshop on Advanced Spectroscopy of Organic Materials for Electronic Applications
  • Place of Presentation: Chiba
  • Year and Date: 2007-10-09
• [Presentation] High-resolution UPS as a Strategy for Finding an Active Organic Material (2007)
  • Author(s): S. Kera, et. al.
  • Organizer: The 4th Workshop on Advanced Spectroscopy of Organic Materials for Electronic Applications
  • Place of Presentation: Chiba
  • Year and Date: 2007-10-08
• [Presentation] Change in molecular conformation of dibenzo-crown ether on graphite surface studied by u1traviolet photoelectron and metastable atom electron spectroscopy (2007)
  • Author(s): T. Hosokai, et. al.
  • Organizer: Europiane conference of molecular electronics 2007
  • Place of Presentation: Metz(France)
  • Year and Date: 2007-09-08
• [Presentation] Spectroscopic evidence of valence interorbital interaction in a lead-phthal ocyanine bilayer film (2007)
  • Author(s): S. Kera, et. al.
  • Organizer: The 15th international conference on vacuum ultla violet radiation physics
  • Place of Presentation: Berlin(Germany)
  • Year and Date: 2007-07-29
• [Presentation] Direct detection of the gap states in C60 thin films by high-sensitivity UPS (2007)
  • Author(s): T. Sueyoshi, et. al.
  • Organizer: The 15th international conference on vacuum ultra violet radiation physics
  • Place of Presentation: Berlin(Gemany)
  • Year and Date: 2007-07-29
• [Presentation] Charge transport in organic semiconductor film: effects of fluorination on the charge reorganization energy of pentacene (2007)
  • Author(s): S. Kera, et. al.
  • Organizer: International workshop on Super-functionality organic devices
  • Place of Presentation: Chiba
  • Year and Date: 2007-07-19
• [Presentation] Electron-phonon coupling measured with high-resolution UPS: Effects of fluorination on the charge reorganization energy of pentacene films (2007)
  • Author(s): S. Kera, et. al.
  • Organizer: 17th International Vacuum Congress, 13th Internati onal Conference on Surface Science, International Conference on Nano Science and Technology
  • Place of Presentation: Stockholm(Sweden)
  • Year and Date: 2007-07-04
• [Presentation] Role of Band Gap States in Pentacene Aggregates: Control of Hole Injec tion Barrier by Fermi-level Pinning (2007)
  • Author(s): S. Kera, et. al.
  • Organizer: The Fourth International Conference on Molecular Electronics and Bicelectronics
  • Place of Presentation: Tokyo
  • Year and Date: 2007-03-15
• [Remarks]
  • URL: http://ulab-www.tf.chiba-u.jp/