Jürgen Thomas

Auger electron spectroscopy study of interdiffusion, oxidation and segregation during thermal treatment of NiCr/CuNi(Mn)/NiCr thin films

Abstract The effect of annealing on sputter deposited thin-films NiCr/CuNi(Mn)/NiCr is studied by Auger electron depth profiling. The samples were annealed to maximum temperatures of 300°C to 550°C and investigated at ambient temperature. Auger transitions of Cu and Ni are separated by target factor analysis, principal component analysis and linear least squares fit to standard spectra. For the CuNi(Mn) layer in the as-received state AES results shows a Cu depletion caused by bombardment induced segregation. After annealing the measured Cu concentration has increased due to Ni diffusion to the interfaces. The NiCr layer is degraded with increasing annealing temperature due to formation of a chromium oxide and diffusion of Ni from the CuNi(Mn) layer. A sequence with nominal compositions near Cr2Ni, CrNi and CrNi2 is found. At the NiCr/CuNi(Mn) interface an interdiffusion zone phase Ni0.6Cr0.2Cu0.2 is formed.

Analytical TEM for the investigation of thin functional layers

Abstract At first a survey of the methodic state of the art in analytical transmission electron microscopy is given. This concerns both the lateral and the analytical resolution, contrast phenomena and electron–solid interactions. The efficiency of the analytical techniques electron nanodiffraction, energy dispersive X-ray spectroscopy (EDXS), and electron energy loss spectroscopy (EELS) is discussed. The possibilities and the limitations of analytical TEM are demonstrated at cross-sections of nanometer scaled multilayers of relevant functional materials. Concentration profiles are taken from EDX and EEL spectra of Fe–Cr and Co–Cu multilayers, which are standard systems for the investigation of giant magnetoresistance (GMR). Furthermore, from the course of the electron energy loss near edge structure (ELNES) conclusions concerning the chemical bonding are possible. This will be discussed for the oxygen bonding in interface regions of the system Al2O3–TiN. The results allow to distinguish between different oxide phases in thin functional layers.

Analysis of nanoscale multilayers by EDXS and EELS in the STEM

After a short description of a model for calculation of element specific linescan intensity profiles measured in an analytical transmission electron microscope on cross-sections of nanoscale multilayers by EDXS and EELS in the STEM mode the essential influences to the results are discussed. Particularly, the signal-to-noise ratio is considered. To confirm the model measured and calculated profiles are compared. Investigations on nanoscale multilayers require a field emission gun and a specimen stage with high stability. Specimen drift can lead to completely confused intensity profiles and has to be avoided or corrected during the measurement.