Energy Level Alignment at Tpd/Etal Interfaces Studied by Kelvin Method

1999 ◽  
Vol 558 ◽  
Author(s):  
N. Hayashi ◽  
E. Ito ◽  
H. Ishii ◽  
Y. Ouchi ◽  
K. Seki
Keyword(s):  
Photoelectron Spectroscopy ◽  
Metal Substrate ◽  
Ultraviolet Photoelectron Spectroscopy ◽  
Level Shift ◽  
Organic Metal ◽  
Metal Interface ◽  
Kelvin Probe ◽  
Vacuum Level ◽  
Initial Stage ◽  
Kelvin Probe Method

ABSTRACTThe vacuum level shift A was determined by Kelvin probe method for TPD/metal systems prepared in ultrahigh vacuum (TPD: N, N'-bis(3-methylphenyl)-N, N'-diphenyl-[1, 1'-biphenyl]-4,4'-diamine). The energy of the vacuum level sharply changed at the initial stage of depositing TPD on the metal substrates, and further bending was not observed up to 100 nm thickness of TPD. This result is consistent with our previous studies of ultraviolet photoelectron spectroscopy. These results indicate the invalidity of traditional model with a common vacuum level at organic/metal interface. We discussed the dependence of the vacuum level shift on the work function Φm of the metal substrate (Au, Cu, Ag, Mg, and Ca). A liner correlation between Δ and Φm was observed only in the region of 3.8 eV < Φm < 4.5 eV, indicating that Fermi level alignment is not achieved at least for some interfaces. We found that Δ for TPD film on the air-exposed metal substrate is smaller than that of TPD on clean metals and was observed a liner relation between Φm and Δ except for the Cu substrate.

Photoemission Study of Metal-Deposited p-Sexiphenyl Film

1999 ◽  
Vol 598 ◽  
Author(s):  
E. Ito ◽  
N. Koch ◽  
H. Oji ◽  
H. Ishii ◽  
G. Leising ◽  
...  
Keyword(s):  
Chemical Reaction ◽  
Photoelectron Spectroscopy ◽  
Electron Spectroscopy ◽  
Alkali Metals ◽  
Ultraviolet Photoelectron Spectroscopy ◽  
Level Shift ◽  
Vacuum Level ◽  
X Ray ◽  
Photoemission Study ◽  
Gap States

ABSTRACTMetal deposition on a p-sexiphenyl (6P) film was studied by ultraviolet photoelectron spectroscopy (UPS), metastable atom electron spectroscopy (MAES), and X-ray photoelectron spectroscopy (XPS). The deposited metals were Au, Mg, and several alkali metals (K, Na, Rb, and Cs). No chemical reaction between 6P and Au or Mg was observed in the measured spectra, while additional gap states appeared in the UPS and MAES spectra by deposition of the alkali metals. The diffusion of Au and Mg atoms into the 6P film was observed in the MAES spectra. We found the trend of the vacuum level shift is different between the systems of the 6P on the Au and its reversed systems (Au on the 6P film), suggesting the different formation of the interface depending on the deposition sequence.

Highly Sensitive Analysis for Valence Band Edge of C60 Films by Total Yield Photoelectron Spectroscopy

1994 ◽  
Vol 349 ◽  
Author(s):  
S. Gonda ◽  
M. Kawasaki ◽  
T. Arakane ◽  
H. Koinuma
Keyword(s):  
Valence Band ◽  
Photoelectron Spectroscopy ◽  
Total Yield ◽  
Kelvin Probe ◽  
Highly Sensitive ◽  
Gap States ◽  
Kelvin Probe Method ◽  
C60 Films ◽  
Simple Picture

ABSTRACTWe have in-situ measured the density of states (DOS) around the top of valence band of pristine C60 films by means of total yield photoelectron spectroscopy. The top of valence band (TVB) of C60 was located at 5.00eV below the vacuum level. Considerable amplitude of gap states was observed up to 0.9eV above the TVB. Kelvin probe method revealed that the Fermi level of amorphous C60 film was located at 0.47eV above the TVB. The improvement of crystallinity in C60 films, which induced the increase in electrical conductivity as well, increased the DOS above the TVB. The electric conduction of C60 films cannot be explained with a simple picture for carrier conduction in semiconductors.

Structural Requirements for Surface-Induced Aromatic Stabilization

2014 ◽  
Vol 1647 ◽  
Author(s):  
Takuya Hosokai ◽  
Keiichirou Yonezawa ◽  
Kengo Kato ◽  
Rintaro Makino ◽  
Jinpeng Yang ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Synchrotron Radiation ◽  
Aromatic Hydrocarbon ◽  
Photoelectron Spectroscopy ◽  
Functional Group ◽  
Ultraviolet Photoelectron Spectroscopy ◽  
Organic Metal ◽  
Structural Requirement ◽  
Structural Requirements ◽  
Aromatic Stabilization

ABSTRACTSurface-induced aromatic stabilization (SIAS), a recently proposed mechanism leading to a formation of charge-transfer (CT) states at organic/metal (O/M) interfaces [G. Heimel, et al., Nat. Chem.5, 187 (2013)], was investigated for an aromatic hydrocarbon, diindenoperylene (DIP), by means of synchrotron radiation-based ultraviolet photoelectron spectroscopy (UPS). By employing DIP and noble metal substrates (Ag and Cu), we confirmed the formation of CT states, indicating that an inclusion of a specific functional group with a hetero-atom within adsorbate molecules as suggested before is not necessarily required for the formation of CT states mediated by the SIAS. With a comparison of the mother and analogue molecules, perylene and PTCDA, we discuss the structural requirement for the realization of the SIAS.

Electronic Structure of Organic/Metal Interfaces Studied by UPS and Kelvin Probe

1999 ◽  
Vol 582 ◽  
Author(s):  
Kazuhiko Seki ◽  
Hiroshi Oji ◽  
Eisuke Ito ◽  
Daisuke Yoshimura ◽  
Naoki Hayashi ◽  
...  
Keyword(s):  
Organic Solar Cells ◽  
Photoemission Spectroscopy ◽  
Organic Layer ◽  
Organic Metal ◽  
Kelvin Probe ◽  
Band Bending ◽  
Light Emitting ◽  
Organic Devices ◽  
Metal Interfaces ◽  
Kelvin Probe Method

ABSTRACTThe interfaces of organic materials with other solids play important roles in the function of various organic devices such as organic light-emitting diodes (OLEDs), spectral sensitization in photography, organic solar cells, and electrophotography. Also they should be important in future molecular devices, both in the central part of the device and at the connection with outside circuits. However, serious experimental examination of such interfaces has started only recently. In this talk we focus our attention on the organic/metal interfaces, and summarize our understanding about (1) the energy level alignment right at the interface, and (2) possible band bending within an organic layer, mainly using the techniques of UV photoemission spectroscopy (UPS) and Kelvin probe method. As for (1), the formation of electric dipole layer was observed in most organic/metal interfaces, and its origin is discussed. As for (2), recent examination of the existence/absence of band bending in ultrahigh vacuum will be reported. It is also pointed out that there can be much effects of (i) atmosphere at sample preparation and measurements, and (2) chemistry and interdiffusion at the interface.

Ultraviolet photoelectron spectroscopy of pristine poly (sodium poly[2-(3-thienyl)-ethoxy-4-butylsulfonate) (PTEBS) and doped with perylene tetracarboxylicdiimide (PTCDI) nanobelts

2009 ◽  
Vol 1212 ◽  
Author(s):  
Leon Rohan Pinto ◽  
Yashdeep Khopkar ◽  
David Keith Chambers ◽  
Mark Koorie ◽  
Orhan Kizilkaya ◽  
...  
Keyword(s):  
Fermi Level ◽  
Photoelectron Spectroscopy ◽  
Self Assembly ◽  
Binding Energies ◽  
Photoemission Spectrum ◽  
Ultraviolet Photoelectron Spectroscopy ◽  
Vacuum Level ◽  
Optoelectronic Application ◽  
And Shifts ◽  
Absorption Characteristics

AbstractWe investigated the possibility of doping poly (sodium poly[2-(3-thienyl)-ethoxy-4-butylsulfonate) (PTEBS) with perylene tetracarboxylicdiimide (PTCDI) nanobelts through ultraviolet photoelectron spectroscopy (UPS) measurements. For our experiment, PTEBS was tuned to absorb maximum light in the range of 450 nm to 550 nm which corresponds to the maximum solar irradiance of the Earth’s atmosphere. Nanobelts of PTCDI were synthesized by gas phase self assembly process. Doping PTEBS with PTCDI nanobelts causes a shift in the Fermi level of the composite material with respect to the vacuum level as observed in the photoemission spectrum. With increased PTCDI doping, PTCDI does not act much like an electron donor, but more like an electron acceptor. The peaks corresponding to the sigma bonds shift towards the vacuum level with higher concentrations of the dopant. Using angled resolved photoemission spectra from a 3m toroidal grating monochromator, PTEBS displays change in the highest occupied molecular orbital in respect to its Fermi level when the side groups were substituted by H+ or OH- groups. The results confirm that the binding energy decreases with increase in activity of the dissolved hydrogen ions. It is evident that there is an increase in the density of states near the Fermi level and shifts to lower binding energies of the occupied molecular orbitals with pH level decrease, which is in agreement with the published optical absorption characteristics of PTEBS. Since UPS data confirm that PTCDI nanobelts dope PTEBS, along with its tunable absorption characteristics, this composite might be a promising material for optoelectronic application.

Energy Level Alignment at Bebq2/PEI/ITO Interfaces Studied by UV Photoemission Spectroscopy

MRS Advances ◽  
2017 ◽  
Vol 2 (42) ◽  
pp. 2261-2266
Author(s):  
Kohei Shimizu ◽  
Hirohiko Fukagawa ◽  
Katsuyuki Morii ◽  
Hiroumi Kinjo ◽  
Tomoya Sato ◽  
...  
Keyword(s):  
Energy Level ◽  
Work Function ◽  
Indium Tin Oxide ◽  
Electron Injection ◽  
Photoemission Spectroscopy ◽  
Level Shift ◽  
Kelvin Probe ◽  
Vacuum Level ◽  
Energy Level Alignment ◽  
Improvement Effect

ABSTRACTA polyethyleneimine (PEI) interlayer has been applied on indium tin oxide (ITO) to improve electron injection in organic devices including inverted organic light-emitting diodes (OLEDs). To understand the improvement effect by PEI insertion, the energy level alignment at bis(10-hydroxybenzo[h]quinolinato)beryllium (Bebq2)/PEI/ITO interfaces was investigated by UV photoemission spectroscopy (UPS). The deposition of a PEI layer was found to reduce the absolute work function of ITO by 1.4 eV. The vacuum level shifts at Bebq2/ITO and Bebq2/PEI interfaces were also determined as 0.3 eV and 0.1 eV in the direction to reduce the electron injection barrier, respectively. Thus the work function reduction by PEI and downward vacuum level shift at the Bebq2/PEI interface can contribute to the improvement effect. Kelvin probe measurement revealed the weak orientation polarization in Bebq2 film with the bottom side positively polarized. This polarization polarity is also advantageous for electron injection in inverted devices.

The Effect of Atmospheric Doping on the Interfacial Electronic Structure of Phthalocyanine Thin Films as Studied by UPS

2005 ◽  
Vol 871 ◽  
Author(s):  
Toshio Nishi ◽  
Kaname Kanai ◽  
Yukio Ouchi ◽  
Martin R. Willis ◽  
Kazuhiko Seki
Keyword(s):  
Photoelectron Spectroscopy ◽  
Field Effect Transistor ◽  
Metal Substrate ◽  
Oxygen Atmosphere ◽  
Ultraviolet Photoelectron Spectroscopy ◽  
Band Bending ◽  
Interfacial Electronic Structure ◽  
Type Semiconductor ◽  
Effect Transistor ◽  
Effect Of Oxygen

AbstractThe effect of oxygen doping on titanyl phthalocyanine (TiOPc) films was investigated by ultraviolet photoelectron spectroscopy (UPS). The energy of the electronic levels of TiOPc films probed by UPS was clearly different between the film deposited in ultrahigh vacuum (UHV) and in oxygen atmosphere. The film deposited in UHV showed downward band bending characteristic of n-type semiconductor. On the other hand, the film deposited in oxygen atmosphere showed upward band bending characteristic of p-type semiconductor. Such trends are in excellent correspondence with reported field effect transistor characteristics. In order to examine the Fermi level (EF) alignment between TiOPc film and the substrate, the HOMO energy of TiOPc relative to the EF of the metal substrate was determined for various substrates. Although EF alignment was not achieved for the TiOPc film prepared in UHV, possibly because of insufficient charge density in the TiOPc film, it was achieved in the case of TiOPc film exposed to oxygen, probably by p-type doping effect of oxygen.

Surface potential of liquid microjet investigated using extreme ultraviolet photoelectron spectroscopy

2020 ◽  
Vol 152 (14) ◽  
pp. 144503
Author(s):  
Junichi Nishitani ◽  
Shutaro Karashima ◽  
Christopher W. West ◽  
Toshinori Suzuki
Keyword(s):  
Surface Potential ◽  
Photoelectron Spectroscopy ◽  
Extreme Ultraviolet ◽  
Ultraviolet Photoelectron Spectroscopy
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