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Papers by Joachim Wollschläger

ACS Applied Materials & Interfaces

Journal of Vacuum Science & Technology A

Reactive molecular beam epitaxy of NiO on Ag(001) has been characterized by high-resolution low e... more Reactive molecular beam epitaxy of NiO on Ag(001) has been characterized by high-resolution low energy electron diffraction performed during deposition of Ni on Ag(001) in molecular oxygen atmosphere for deposition temperatures of 300–420 K. The initial stage of film growth at high deposition temperature is determined by competing processes of Ni oxidation and Ni interdiffusion into Ag(001) with Ni-Ag alloying. Ni oxidation is favored at low deposition temperatures. Thus, NiO bilayers are immediately formed. At high deposition temperatures, however, alloying with Ag is enhanced and the formation of the initial NiO bilayer is delayed. After formation of a closed NiO bilayer, alloying is prevented and all deposited Ni is oxidized and NiO growth proceeds in the layer-by-layer growth mode. Later stages of epitaxy are governed by relaxation processes induced by the formation of mosaics due to interface dislocations. The tilt angle of the mosaic decreases with increasing film thickness du...

Physics of Solid Surfaces, 2018

This chapter discusses the structure of domain boundary in Fe3O4 films on MgO(001) measured using... more This chapter discusses the structure of domain boundary in Fe3O4 films on MgO(001) measured using various experimental techniques.

Physics of Solid Surfaces, 2018

This chapter discusses the structure of domain boundary in Al2O3 binary oxide measured using vari... more This chapter discusses the structure of domain boundary in Al2O3 binary oxide measured using various experimental techniques.

In this chapter the coexistence of domains in gold observed using various experimental techniques... more In this chapter the coexistence of domains in gold observed using various experimental techniques are discussed in detail.

Physica B: Condensed Matter, 2020

Materials Research Express, 2014

ABSTRACT Iron oxide films with different thicknesses (7.6–30 nm) were grown on clean MgO(001) sub... more ABSTRACT Iron oxide films with different thicknesses (7.6–30 nm) were grown on clean MgO(001) substrates using reactive molecular beam epitaxy at 250 °C depositing Fe in a 5 × 10−5 mbar oxygen atmosphere. X-ray photoelectron spectra and low energy electron diffraction experiments indicate the stoichiometry and the surface structure of magnetite (Fe3O4). Film thicknesses and the lattice constants were analyzed ex situ by x-ray reflectometry and x-ray diffraction, respectively. These experiments reveal the single crystalline and epitactic state of the iron oxide films. However, the obtained vertical layer distances are too small to be strained magnetite and would rather suit to maghemite. Although Raman spectroscopy carried out to analyze the present iron oxide phase showed that the films might have slightly been oxidized in ambient conditions, a posteriori performed XPS measurements exclude a strong oxidation of the surface. Therefore we consider the presence of anti phase boundaries to explain the low vertical layer distances of the magnetite films. Further magnetooptic Kerr measurements were performed to investigate the magnetic properties. While the thinnest film shows a magnetic isotropic behavior, the thicker films exhibit a fourfold magnetic in-plane anisotropy. The magnetic easy axes are in the Fe3O4 <110> directions. We propose that the magnetocrystalline anisotropy is too weak for very thin iron oxide films to form fourfold anisotropy related to the cubic crystal structure.

Results in Physics, 2017

In this paper chromium oxide (Cr 2 O 3) thin films have been prepared onto MgO (001) substrate by... more In this paper chromium oxide (Cr 2 O 3) thin films have been prepared onto MgO (001) substrate by thermal evaporation method at a pressure of about 1×10-4 Pa. The morphology of the obtained thin films was investigated. These films show homogeneous and uniform distribution according to AFM images. The XPS measurements of chromium Cr 2p and oxygen O 1s peaks shows a good agreement when compared with another works cited in the literature. The micro-structural analysis, surface morphology and optical properties in the grown films were achieved using X-rays Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM), and Ultraviolet Visible (UV-Vis) spectroscopy.

$Research paper thumbnail of Defects at the Si(111)/SiO2interface investigated with low-energy electron diffraction$