ELECTRON SPECTROSCOPY

Members
M. Sc. Oleksandr Selyshchev Former Members: Dr. Volodymyr Dzhagan, Dr. Daniel Lehmann, Dr. Francisc Haidu, M.Sc. Ghazal Tofigi,

Members

Former Members:

Dr. Volodymyr Dzhagan, Dr. Daniel Lehmann, Dr. Francisc Haidu,
M.Sc. Ghazal Tofigi,

Topics
Material characterization and chemical interaction of interfaces (XPS) Ultra-high vacuum studies of growth and electronic properties of various organic films (e.g. perylene derivatives, phthalocyanines) on various substrates (GaAs, Si) (XPS and UPS) Determination of the electronic structure of solids surfaces, thin films, and relevant interfaces via inspection of valence and conduction bands (UPS and IPES) Determination of band offsets as well as HOMO (UPS) and LUMO levels (IPES) of organic films Angle-resolved characterization permits the mapping of band structure in k-space (UPS) Near Edge X-ray Absorption Fine Structure (NEXAFS) investigations at the electron storage ring BESSY II

Topics

Material characterization and chemical interaction of interfaces (XPS)
Ultra-high vacuum studies of growth and electronic properties of various organic films (e.g. perylene derivatives, phthalocyanines) on various substrates (GaAs, Si) (XPS and UPS)
Determination of the electronic structure of solids surfaces, thin films, and relevant interfaces via inspection of valence and conduction bands (UPS and IPES)
Determination of band offsets as well as HOMO (UPS) and LUMO levels (IPES) of organic films
Angle-resolved characterization permits the mapping of band structure in k-space (UPS)
Near Edge X-ray Absorption Fine Structure (NEXAFS) investigations at the electron storage ring BESSY II

Equipment
ARUPS 10 for UV Photoemission Spectroscopy (UPS) and Inverse Photoemission Spectroscopy (IPES) MUSTANG for X-ray Photoemission Spectroscopy (XPS)

Examples

Figure 1 illustrates the principles of direct photoemission (blue) and its complementary technique inverse photoemission (red), along with the correspondingly acquired electronic structure of an organic film. The figure also presents the fundamental parameters of organic films directly probed by the photoemission characterization such as Highest Occupied Molecular Orbital (HOMO), Lowest Unoccupied Molecular Orbital (LUMO), Electron Affinity (EA), Ionization Energy (IE), and work function (Φ) related to the Fermi level (E_F) and vacuum level (E_VAC).	Figure 2 presents combined photoemission (below E_F) and inverse photoemission spectra (above E_F) of a 15 nm thick film of DiMe-PTCDI employed for the determination of its transport gap.	Figure 3 presents carbon K-edge NEXAFS spectra of a PTCDA film as a function of photon incidence angle, Θ. The features located at 284-290 eV and above 290 eV represent π* and σ* resonances, respectively. Their relative intensities can be used to determine the molecular orientation.

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