Compound materials have shown stable and enhanced optical performance in soft x-ray energy region. However, the growth related change in structural and chemical properties lead to affect their ...performances. In the present study, thin films of different thicknesses of ZrC compound material were deposited on Si (100) substrate. Optical response of ZrC thin film was measured in soft x-ray energy region using Indus-1 reflectivity beamline. It was found that the soft x-ray reflectivity data of ZrC thin films cannot be explained with Henke's tabulated data. To understand this disagreement a detailed structural and chemical investigation was carried out using x-ray reflectivity, grazing incidence x-ray diffraction, atomic force microscopy and x-ray photoelectron spectroscopy techniques. It was found that the presence of unreacted carbon along with small oxygen in ZrC matrix is responsible for variation in optical constant value. Details of the investigations are discussed.
•ZrC thin films of different thicknesses were deposited by ion beam sputtering.•We found that Henke's data cannot explain the soft x-ray optical response of ZrC.•Structural studies were performed using several techniques (XRR, GIXRD, AFM and XPS).•Films were poly-crystalline with near bulk density and smooth surface morphology.•Mismatch in SXR data can be explained from unreacted carbon and oxygen in ZrC matrix.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Hydrocarbon cracking and carbon contamination of optical elements in soft X-ray spectrometers and synchrotron radiation beamlines is a severe problem. Carbon contamination seriously affects the ...optics performance. In the present work, an Nd:YAG laser providing 2mJ of pulse energy and 100ns of pulse duration has been used for carbon cleaning experiments. The laser cleaning is a non-contact, accurate, efficient and safe process. A surface area of 48cm2 having ∼20nm thick carbon layer on gold surface has been removed with six number of laser passes and with 80% laser spot overlapping without any change in surface roughness of the underneath gold film. Effect of laser beam on gold film after carbon removal has been analyzed using X-ray photoelectron spectroscopy, soft X-ray reflectivity techniques. Atomic force microscopy was used to analyze surface morphology before and after laser cleaning process. Power spectral density function was calculated over large frequency range of 10−1 to 10−4nm−1 to understand topographic data.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A microfocus X‐ray fluorescence spectroscopy beamline (BL‐16) at the Indian synchrotron radiation facility Indus‐2 has been constructed with an experimental emphasis on environmental, archaeological, ...biomedical and material science applications involving heavy metal speciation and their localization. The beamline offers a combination of different analytical probes, e.g. X‐ray fluorescence mapping, X‐ray microspectroscopy and total‐external‐reflection fluorescence characterization. The beamline is installed on a bending‐magnet source with a working X‐ray energy range of 4–20 keV, enabling it to excite K‐edges of all elements from S to Nb and L‐edges from Ag to U. The optics of the beamline comprises of a double‐crystal monochromator with Si(111) symmetric and asymmetric crystals and a pair of Kirkpatrick–Baez focusing mirrors. This paper describes the performance of the beamline and its capabilities with examples of measured results.
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BFBNIB, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Multilayer period thickness changes for various thickness ratios, Γ (ratio of W layer thickness to period thickness) as a function of annealing temperatures were studied by grazing incidence X-ray ...reflectivity (GIXRR), and grazing incidence X-ray diffraction (GIXRD). Both period thickness expansion and compression were observed depending upon Γ and annealing temperatures. Multilayer with the W layer thickness close to the B4C layer has undergone less period thickness changes. Successive appearance and disappearance of multilayer Bragg maxima in GIXRR were observed. Such behavior suggested that redistribution of atomic density within bilayer, the displacement of interface and the multilayer period thickness change as annealing proceeds. GIXRD measurements performed using synchrotron radiation suggested the formation of phases corresponding to tungsten boride and carbide.
•We reported the influence of the layer thickness on thermal stability of W/B4C multilayers.•Depending on the layer thickness ratio, the period variation can be positive or negative.•Diffusion induced structural changes can be minimized by optimizing layers thickness ratio.•Tungsten carbide and boride phases observed at elevated temperatures.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The K–L total vacancy transfer probabilities (η
KL
) of some 3d elements have been determined using Indus-2 synchrotron radiation. The targets, such as Cr, Cu, and Zn, are excited by using 6.5, 10, ...and 11 keV synchrotron radiation, respectively. The K X-ray photons are detected with a silicon drift detector, which has an energy resolution of 130 eV at 5.9 keV. By measuring the K-shell fluorescence yield and K X-ray intensity ratio, the K–L vacancy transfer probabilities have been determined. Measured values have been compared with the theoretical values and other experimental values.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Element‐specific structural analysis at the buried interface of a low electron density contrast system is important in many applied fields. The analysis of nanoscaled Si/B4C buried interfaces is ...demonstrated using resonant X‐ray reflectivity. This technique combines information about spatial modulations of charges provided by scattering, which is further enhanced near the resonance, with the sensitivity to electronic structure provided by spectroscopy. Si/B4C thin‐film structures are studied by varying the position of B4C in Si layers. Measured values of near‐edge optical properties are correlated with the resonant reflectivity profile to quantify the element‐specific composition. It is observed that, although Si/B4C forms a smooth interface, there are chemical changes in the sputtered B4C layer. Nondestructive quantification of the chemical changes and the spatial distribution of the constituents is reported.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
In the present study we report a new multilayer combination comprised of refracting layers of niobium carbide and spacer layers of silicon as a more stable and high reflecting combination for the 10 ...- 20 nm wavelength region. The reflectivity of the new combination is comparable to Mo/Si conventional mirrors. Annealing experiments carried out with NbC/Si multilayer at 600°C temperature showed a ~2.5% drop in the soft x-ray reflectivity along with a marginal contraction in the multilayer period length. The multilayer structure is found stable after the heat treatment. Crystallization of the niobium carbide and silicon layers is responsible for the compaction in the period length as revealed by the grazing incidence x-ray diffraction measurements. No signature of silicide formation or any other chemical species could be detected. The multilayer structures were grown by ion beam sputtering technique using a compound target of niobium carbide. Soft x-ray reflectivity measurements performed at the Indus-1 and BESSY-II synchrotron radiation sources are found in good agreement with the simulations.
Microstructure limited reflectivity of sputter deposited ultra-short period W/B4C multilayers (MLs) has been studied using x-ray reflectivity, diffuse scattering and transmission electron microscopy ...(TEM). In order to understand the W-B4C interface in the near-discontinuous range, the thickness of the constituent layers was systematically varied between 0.5 nm and 2.5 nm. Good density contrast and minimal thickness error were observed in MLs with individual layer thickness higher than ~1.1 nm. However, below 1.1 nm one enters into a regime where the individual layers become discontinuous, leading to embedded growth of the two constituent layers. Consequently, a significant loss of x-ray contrast was observed. In addition, increased area of contact between W and B4C enhances the fraction of tungsten compound resulting in a layer thickness error. Based on these findings, large repetition (upto 400 bilayers) MLs with ultra-short period (down to 1.6 nm) were optimized to achieve reflectivity as high as 53% and resolving power of 149, at 8.047 keV.
We report the results of growth kinetics of oxidation process on niobium thin film surfaces exposed to air at room temperature by using a surface sensitive non-destructive X-ray reflectivity ...technique. The oxidation process follows a modified Cabrera–Mott model of thin films. We have shown that the oxide growth is limited by the internal field due to the contact potential which develops during the initial stage of oxidation. The calculated contact potential for 100 and 230
Å thick films is 0.81
±
0.14 and 1.20
±
0.11
V respectively. We report that 40% increase in the contact potential increases the growth rate for the first few mono layers of Nb
2O
5 from ∼2.18 to ∼2790
Å/s. The growth rates of oxidation on these samples become similar after the oxide thicknesses of ∼25
Å are reached. We report on the basis of our studies that a protective layer should be grown in situ to avoid oxidation of Nb thin film surface of Nb/Cu cavities.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We present precise measurements of atomic distributions of low electron density contrast at a buried interface using soft x-ray resonant scattering. This approach allows one to construct chemically ...and spatially highly resolved atomic distribution profile upto several tens of nanometer in a non-destructive and quantitative manner. We demonstrate that the method is sensitive enough to resolve compositional differences of few atomic percent in nano-scaled layered structures of elements with poor electron density differences (0.05%). The present study near the edge of potential impurities in soft x-ray range for low-Z system will stimulate the activity in that field.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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