A comprehensive study on the growth of nanoscale transition metal-on-transition metal (TM-on-TM) systems is presented. The near room-temperature intermixing and segregation phenomena during growth are studied in vacuo using high-sensitivity low-energy ion scattering. The investigated TM-on-TM systems are classified into four types according to the observed intermixing and segregation behavior. Empirical rules are suggested to qualitatively predict the growth characteristics of any TM-on-TM system based on the atomic size difference, surface-energy difference, and enthalpy of mixing between the film and substrate atoms. An exponential trend is observed in the effective interface width as a function of the surface-energy difference between the film and substrate layers, with a subtrend based on the crystal structure of the TM layers. A semiempirical model that accurately describes the experimental data is presented. It serves as a scaling law to predict the effective interface width and the minimum film thickness required for full film coverage in TM-on-TM systems in general. The ability to predict the growth characteristics as well as the interface width for any TM-on-TM system significantly contributes to the process of finding the best material combination for a specific application, where layer growth characteristics are implicitly considered when selecting materials based on their functional properties.

Low Energy Ion Scattering (LEIS) has been performed on several lanthanum-based surfaces. Strong subsurface matrix effects-dependence of surface scattered He+ ion yield on the composition of subsurface layer-have been observed. The ion yield of He+ scattered by La differed by a factor of up to 2.5 for different surfaces, while only the La peak was visible in the spectra. To study these effects and enable surface quantification, He+ ion yields have been measured in a range of incident He+ energies from 1000 to 7500 eV for LaB6, La2O3, oxidized La and pure La surfaces. The investigation showed that as many as two simultaneous matrix effects are present, each one driven by a separate charge exchange mechanism. The first one is a resonant neutralization from the conduction band of La to an excited state of the He+ ion. It depends on the work function of the surface, which is lowered significantly when La interacts with O or B. The second mechanism is quasiresonant charge transfer between bound La levels and He 1s, which creates characteristic oscillations in the energy dependence of ion yields. The exact structure of the oscillations depends on small changes in binding energies of interacting La levels. This is the first time quasiresonant charge transfer is proven to be present in La. It is likely that La 5p orbitals participate in this resonance, which can be the first clear observation of a resonance between p and s orbitals in LEIS. This type of resonance was previously believed to be absent because of strong damping. We also demonstrated that despite the complex matrix effect precise measurements over a wide energy range allow quantification of the atomic composition of La-based surfaces.

Correspondence email: a.zameshin@utwente.nl Synopsis A custom free-form approach is used for reconstruction of GIXRR from periodic multilayers, simulated and experimental data fits are presented.Abstract Grazing Incidence X-ray Reflectivity (GIXRR) is a widely used analysis method for thin films and multilayer structures. However, conventional so-called model-based approaches of structural reconstruction from GIXRR data are lacking analytical power when dealing with very thin structures (down to the nm scale), because a priori assumptions have to be made about the interface composition and structure. This makes it very difficult to reliably analyse such structures. In this work custom freeform approach is presented which solves this task without the need for a priori assumptions on layer or interface parameters. As a proof of principle, a perfect optical constant profile reconstruction and GIXRR curve matching for the simulated data are demonstrated. The developed approach is used to analyse structures of multilayer LaN/B Bragg reflectors designed for the Extreme UV range. Performed analysis allowed to reveal the difference in optical constant profiles of these structures produced with different processes. The uncertainties of structural reconstruction are also discussed.

The effect of ion polishing in sputter deposited W/Si multilayer mirrors with a d-spacing of 2.5 nm was studied. 0.1 to 0.5 nm of Si were etched with 100 eV Ar+ ions. This process resulted in a pronounced reduction in diffused scattering, measured at wavelengths about 0.1 nm. However, CuKa X-ray specular reflectivity and AFM showed only a marginal reduction of the roughness amplitude in the systems. Furthermore, the soft X-ray reflectivity at 0.84 and 2.4 nm did not show any changes after the ion polishing as compared to the nonpolished structures. Grazing incidence X-ray reflectivity (GIXR) analysis revealed that there was no pure W present in the deposited multilayers, with WSi2 being formed instead. As a result, it was concluded that the initial roughness in W/Si multilayers grown by magnetron sputtering is not the major factor in the reflectivity deviation from the calculated value for an ideal system. Nevertheless, the grazing incidence small-angle X-ray scattering (GISAXS) analysis revealed that ion polishing reduces the vertical propagation of roughness from layer to layer by a factor of two, as well as favorably affecting the lateral correlation length and Hurst parameter. These improvements explain the reduction of diffused X-ray scattering at 0.1 nm by more than an order of magnitude, which is relevant for applications like high resolution XRD analysis.

Electronic properties of thin films differ at the interfaces as well. For example, Schottky barriers are an important effect of metal-semiconductor interfaces [12]. These effects are even more important for organic semiconductors [13].The performance of multilayer structures for optical applications also strongly depends on interface properties. This topic is discussed in the next section. 1 8 1.4. Analysis of thin film interfaces ExperimentalBefore I came here, I was confused about this subject. Having listened to your lecture, I am still confused -but on a higher level.