ABSTRACT
Correction for 'Depth-resolved oxidational studies of Be/Al periodic multilayers investigated by X-ray photoelectron spectroscopy' by Niranjan Kumar et al., Phys. Chem. Chem. Phys., 2023, 25, 1205-1213, https://doi.org/10.1039/D2CP04778K.
ABSTRACT
The quantification of surface and subsurface oxidation of Be/Al periodic multilayer mirrors due to exposure in the ambient atmosphere was investigated by depth-resolved X-ray photoelectron spectroscopy. The contribution of oxidation was lower for the thicker layer of Al in the periodic structures since the surface was less chemically reactive for the oxidation. This was investigated by finding the depth-resolved slope of the intensity ratio of metal/oxides (Be/BeOx and Al/AlOx) by analyzing the chemical shift of Al 1s and Be 1s photoelectrons. Furthermore, a well-resolved doublet chemical shift in the O 1s spectra indicated the formation of BeOx/AlOx and BeOH/AlOH oxides. The investigation showed that the subsurface and surface regions were dominated by metal-hydroxide (BeOH/AlOH) and metal-oxide (BeOx/AlOx) bonding, respectively, analyzed by the depth-resolved chemical shifts.
ABSTRACT
In periodic W/Be multilayers, thickness-dependent microstructural and phase modifications were investigated in W and Be layers. In X-ray diffraction, α-W was predominant for the ultrathin layer of W, while ß-W evolved along with the α-W phase for higher film thickness. For the thicker layers, the thermodynamically metastable ß-W vanished and a single well-defined preferably oriented stable α-W phase was observed. The lattice spacing revealed that these phases exist in the tensile stressed condition. With the increase in thickness of Be layers, the blueshift and narrow linewidth of the transverse optical (TO) phonon mode was observed in Raman scattering studies. However, the TO mode was redshifted and the linewidth was further narrowed consistently with an increase in the thermal annealing temperature of the multilayers. The investigation has quantified an increase in compressive strain and reduction of defects with an increase in thickness of the Be layers. However, for thermally annealed samples, the compressive strain in the Be layers was relaxed and crystalline quality was improved.
ABSTRACT
In the present paper, the formation of an interface region in the multilayer periodic Mo/Be structure with/without a B4C or Si barrier layer depending on the annealing conditions was studied using X-ray photoelectron spectroscopy. The formation of different beryllides at the interfaces Be-on-Mo and Mo-on-Be was explained by the impact of the deposition-induced exchange caused by ballistic collisions and surface free energy. The influence of the high temperatures on the thermal stability of Mo/Be multilayer systems without/with a barrier layer was studied. Since the appropriately selected barrier layers prevent the formation of the interlayer region of mirrors at room temperature, it was concluded that it would also lead to a weakening of interlayer diffusion in multilayer mirrors at higher temperatures. The effect of barrier layer insertion on the thermal stability of Mo/Be structures was analyzed in detail. It was established that regardless of the material, the introduction of a barrier layer: (i) limits the formation of beryllides with an increase in the annealing temperature at the Be-on-Mo interface; (ii) prevents the formation of MoBe2, while forming MoBe12 beryllide at the Mo-on-Be interface; and (iii) does not limit the beryllium oxidation process at the Mo-on-Be interface.
ABSTRACT
In the present study, the formation of intermediate compounds in the Mo/Si multilayer was realized by the introduction of barrier layers at the interfaces. Their impact on the interdiffusion of Mo and Si was analyzed via X-ray photoelectron spectroscopy. It was established that the insertion of a thin Be barrier layer led to the formation of beryllide MoBe12 at the interface Si-on-Mo, which prevented the formation of molybdenum disilicide and improved the interface. The insertion of the B4C barrier layer led to its complete decomposition with the formation of borides and carbides of molybdenum and silicon (MoBx, SiBx, MoxC and SiCx) at the Si-on-Mo interface. The formation of only MoBx and SiCx was detected at the Mo-on-Si interface. It was important that the insertion of a thin B4C barrier layer did not fully prevent the formation of MoSi2 at both (Si-on-Mo and Mo-on-Si) the interfaces. These facts allowed us to assume that the diffusion barrier function of the B4C interlayer could be caused by the stability of the formed compounds, rather than the stability of the B4C layer itself.
ABSTRACT
We present an approach adapted to study the interface (composition and extension) of X-ray multilayer mirrors using angle resolved photoelectron spectroscopy (ARXPS). In the approach we rely on the concept of the average effective attenuation length (EAL) of the photoelectron and not on the inelastic mean free path (IMPF), which allows us to take into account the contribution of elastically scattered electrons and to increase the accuracy of the determined thickness of the layers. We apply the developed approach to study the formation of interfaces in a multilayer periodic Mo/Si mirror. The chemical composition and significance of the interfaces depending on the number of periods were investigated by means of the ARXPS spectra decomposition technique. Formation of a molybdenum silicide MoSi2 at the interfaces was revealed. It was shown that molybdenum silicide with different thicknesses is formed at the interfaces depending on the film order. In addition, it was established that increasing the period number of the [Mo/Si] system leads to a decrease of the interface extension.
ABSTRACT
The He-II (λ=30.4 nm) emission line is one of the spectral channels chosen to study solar corona. This Letter reports on investigations of novel beryllium (Be)/magnesium multilayer coatings which, when incorporated beneath a protective bilayer of aluminium and Be, ensure particularly high-reflection coefficients of up to 56%, a spectral width of Δλ=1.6 nm (λ/Δλ≈20), and high temporal stability.
