0000000000671622
AUTHOR
Stefan Krischok
A comparative analysis of electron spectroscopy and first-principles studies on Cu(Pd) adsorption on MgO
Ultrathin MgO films were grown on a W(1 1 0) substrate while metastable impact electron (MIES) and photoelectron (UPS) spectra were measured in situ; apart from the valence band emission, no additional spectral features were detected. The oxide surface was exposed to metal atoms (Cu, Pd) at RT. A comparison with the DOS extracted from first-principles DFT calculations shows that the metal-induced intensity developing above the top of the O 2p valence band in the UP spectra under Cu(Pd) exposure is caused by Cu 3d (Pd 4d) emission. The emission seen in the MIES spectra is attributed to the ionization of Cu 3d and 4s states of adsorbed neutral Cu atoms in an Auger process, Auger neutralizatio…
The surface electronic structure of stoichiometric and defective LiF surfaces studied with MIES and UPS in combination with ab-initio calculations
Abstract UPS (He I) and metastable impact electron spectroscopy (MIES) spectra of the LiF(100) single crystal surface and stoichiometric LiF films are presented. The spectra are interpreted on the basis of ab-initio electronic structure calculations. Defective surfaces, produced by electron dosing, were studied in the same manner. The MIES spectra reveal that the electron dosing produces metallic patches on the surface, but no uniform Li adlayer. The calculation show that the F-center contribution to the electron emission is very close in energy to that from the metallic patches; thus, the two contributions cannot be distinguished by the present experimental techniques.
Characterization of LiF and CaF2 surfaces using MIES and UPS (HeI)
Metastable impact electron spectroscopy (MIES) and UPS (HeI) in combination with ab initio calculations (CRYSTALcode) were applied to study surface and bulk defects in LiF and CaF2. The investigated stoichiometric, defective and doped surfaces are LiF, LiF doped with Mg, and CaF2. The experimental information obtained on the electronic structure of stoichiometric and defective surfaces of LiF (100), LiF on W (110) and CaF2 (111) is discussed on the basis of the ab initio calculations. MIES spectra show features from Li agglomerates on the surface of electron bombarded LiF. The electronic structure of the LiF:Mg single crystal shows additional features above the valence band maximum caused b…
Low vacuum photo electron emitting thin films
Impact ionisation is a standard procedure to ionise gaseous or vaporisable substances in organic mass spectrometry. In this work, a "softer" ionisation is introduced which seems to be an alternative ion source for reducing collision between substance molecules and the hot internal walls of the box. Through collision mainly found in impact ionisation sources, fragments are built especially from thermally sensitive substances falsifying the spectra. We present here photoelectron emitting materials for the soft ionisation using semiconducting compounds, galliumn nitride (GaN), and a representative of the borides, lanthanum hexaboride (LaB 6 ). They are evaluated by photoelectron spectroscopic …