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An ultrahigh vacuum apparatus for investigations of ferromagnetic samples allowing the variation of detection angle and spin resolution of secondary and photoelectrons is described. Angle variation is facilitated by a special combination of 180° and 90° deflectors and a cylindrical sector analyzer serves as energy dispersing element. Spin analysis is carried out using a hemispherical high energy (90 keV) Mott polarimeter without retarding potentials. Its efficiency was determined as 2.4×10−4. Due to acceleration in a short spherically symmetric field, the setup is rather compact and the sensitivity to geometrical misalignment is small. The performance of the instrument is demonstrated by angle dependent measurements of thin ferromagnetic Co(0001) films, evaporated on W(110), and modifications of surface magnetic properties of a xenon adsorbate layer.

Abstract. Mo/Si multilayers are fabricated by electronbeam evaporation in UHV at different temperatures (30 ° C, 150 ° C, 200 ° C) during deposition. After completion their thermal stability is tested by baking them at temperatures (Tbak) between 200°C and 800°C in steps of 50°C or 100 ° C. After each baking step the multilayers are characterized by small angle CuK -X-ray diffraction. Additionally, the normal incidence soft-X-ray reflectivity for wavelengths between 11 nm and 19 nm is determined after baking at 500 ° C. Furthermore, the layer structure of the multilayers is investigated by means of Rutherford Backscattering Spectroscopy (RBS) and sputter/Auger Electron Spectroscopy (AES) technique. While the reflectivity turns out to be highest for a deposition temperature of 150 ° C, the thermal stability of the multilayer increases with deposition temperature. The multilayer deposited at 200 ° C stands even a 20 min 500 ° C baking without considerable changes in the reflectivity behaviour. 68.55, 68.65, 78.65 In the wavelength range between 13 nm and 30 nm the combination of Mo and Si is most widely used for normalincidence multilayer mirrors. Reflectivities around 60% have been achieved with both sputtering [1] and e -beam evaporation in combination with thermal treatments during deposition [2,3]. Besides a high value for the reflectivity, the stability of the multilayer stack is also an important property, since applications include for example synchrotron radiation optics, where the multilayer can be heated to a few hundred degrees Celsius [4]. The long-term stability is also important for a number of applications. PACS:The thermal stability of Mo/Si multilayers has been studied earlier in several works [5][6][7][8][9][10][11] but in all of them the multilayers are fabricated by sputtering. In [12] it is shown that thermal treatment during e--beam deposition can considerably enhance the reflectivity of Mo/Si multilayer * Present address: European Synchrotron Radiation Facility, F-38043 Grenoble, France mirrors with a double layer spacing of about 7.5 nm. For a deposition temperature (Tdep) of 150°C the reflectivity is about a factor of two larger than the reflectivity of the 30 ° C and 200 ° C sample [12,13]. In other previous works [14,15] the influence of the deposition temperature on the microstructure of Mo/Si-multilayer systems fabricated by e--beam evaporation was studied. They have shown that Mo/Si muttilayers have interlayers of a mixture of Mo and Si at the Mo-Si interfaces and that the thickness of Mo-on-Si interlayers increases with increasing deposition temperature, while the thickness of the Si-on-Mo interlayers keeps constant. In our work the influence of the different microstructure for the multilayers which were deposited at different temperatures on the thermal stability is also investigated.

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High resolution Rutherford backscattering spectroscopy with an electrostatic analysis of the ion energy is applied to Mo/Si multilayers with a period of 7 nm. The multilayers have been produced for X-ray optical purposes by electron beam evaporation in ultrahigh vacuum at three different temperatures during deposition: 30, 150 and 200 °C. In the Rutherford backscattering spectra the layer structure is resolved in all three cases. The muitilayers deposited at 150 and 200 °C show interlayers of mixed Mo and Si of different thicknesses on the two sides of a Mo layer. The most distinct layer structure is found for the 150 °C sample, whereas the spectra for the 30 °C sample indicate a larger interfacial roughness and those for the 200 °C sample larger interfacial layers of mixed Mo and Si than for the 150 °C sample. On baking the multilayers to temperatures higher than 400 °C, interdiffusion of Mo and Si is observed. The multilayers deposited at 150 and 200 °C are destroyed after baking to 600 °C, whereas the multilayer deposited at 30 °C has already been destroyed after baking to 500 °C. Up to a baking temperature of 600 °C neither losses of material from the stack nor accumulation of Mo or Si at the surface or the interface between the stack and substrate are observed.