Rev.Sci.Instrum.95,023904(2024) https://doi.org/10.1063/5.0190169

The soft x-ray energy region available from Indus-2 offers a great opportunity to pursue fundamental studies and carryout new technological developments. In the soft x-ray region x-ray reflectivity becomes very powerful tool to probe low contrast system such as carbonaceous soft condensed matter films as it enables one to enhance the contrast among low Z elements near the absorption edges of respective elements. A reflectometry facility has been setup at Indus-2 synchrotron source to pursue various pure and applied research programs

The Beamline	Inside view of monochromator

Optical layout and beamline parameters

1. The soft x-ray reflectivity beamline uses a constant deviation angle variable line spacing plane grating monochromator with Hettrick type optics.
2. The first optical element of the beamline is a horizontally deflecting and vertically mounted toroidal mirror, TM1, which accepts 2 mrad (H) and 3 mrad (V) of the emitted bending magnet radiation.
3. TM1 focuses the light vertically on to the entrance slit S1, and horizontally on to the exit slit S2.
4. The second mirror is a spherical mirror SM, which is vertically deflecting and forms a convergent beam on the plane grating.
5. Three interchangeable gratings G1, G2 and G3 of line densities 1200, 400 and 150 lines/mm are used to efficiently cover the whole energy region of 100 - 1500 eV.

Experimental Techniques

The experimental station consists of a two -axes high -vacuum compatible goniometer with x-y-z sample manipulation stages. The scattering geometry is in the vertical plane which is suitable for s-polarized reflectivity measurements as synchrotron light is plane polarized in the horizontal plane.

The existing sample holder can accommodate a sample of size up to 300 mm length, 100 mm width and 50 mm height. The maximum weight of the sample in existing configuration can be about 5 Kg. Detector distance from the axis of rotation is 300 mm.

Application Areas

The experimental station of the beamline is a versatile instrument to measure the x-ray reflectivity, x-ray absorption and x-ray fluorescence signals in the soft x-ray region. These techniques provide information about the materials composition, electronic properties and structural information about the thinfilm/ multilayer samples, surface/interface roughnesses, density profiles etc. These techniques have broad application areas in materials science, condensed matter chemistry, x-ray instrumentations, etc.

Reflectivity performance of reflective optics of ~300 mm length can be performed.

Detector active area of 50 mm x 50 mm can be scanned. Overall size of the detector should be within ~300 mm length, ~150 mm width and ~50 mm height.

Angle dependent reflectivity technique is applied to analyse the depth profiles of a thinfilm and multilayer structures.

Soft x-ray fluorescence, Soft x-ray absorption and near edge Soft x-ray reflectivity techniques together are used for chemical and electronic structure analyses of thinfilms and other suitable samples

Science Highlights

Evidence of spin-phonon interactions in MgCu2O3: low temperature Raman studies Phys. Scr. 99, 095910 (2024) https://doi.org/10.1088/1402-4896/ad67b0

A versatile beamline for soft x-ray reflectivity, absorption, and fluorescence measurements at Indus-2 synchrotron source Rev. Sci. Instrum. 95, 023904 (2024) https://doi.org/10.1063/5.0190169

Effect of electronic transitions on near edge optical properties of off-stoichiometric boron carbide thin films J. Appl. Phys. 133, 165302 (2023). https://doi.org/10.1063/5.0145828

Assessment of bonding character of β-(AlxGa1-x)2O3 alloys from photoluminescence and x-ray absorption near edge spectroscopy Appl. Phys. Lett. 122, 152104 (2023). https://doi.org/10.1063/5.0148800

Boron migration during amorphous to crystalline transformation in CoFeB/MgO multilayers: A reflectivity study Materials Research Bulletin 161, 112150, (2023) https://doi.org/10.1016/j.materresbull.2023.112150

Interface analysis of Mg/Sc and Sc/Mg bilayers using X-ray reflectivity Thin Solid Films 763, 139595 (2022). https://doi.org//10.1016/j.tsf.2022.139595

Study of interface reaction in a B4C/Cr mirror at elevated temperature using soft X-ray reflectivity J. Synchrotron Rad. 29 (2022) https://doi.org/10.1107/S1600577522004738

Electronic structure modification in Fe-substituted β-Ga2O3 from resonant photoemission and soft x-ray absorption spectroscopies J. Phys. D: Appl. Phys. 55, 185304 (2022) https://doi.org/10.1088/1361-6463/ac43dc

Investigation of soft X-ray optical properties and their correlation with structural characteristics of zirconium oxide thin films Thin Solid Films 721 (2021) 138552 https://doi.org/10.1016/j.tsf.2021.138552

Interface modification of Cr/Ti multilayers with C barrier layer for enhanced reflectivity in the water window regime J. Synchrotron Rad. 28 (2021) 224–230 https://doi.org/10.1107/S1600577520013429

Carbon removal from a mirror-like gold surface by UV light, RF plasma, and IR laser exposure: a comparative study Applied Optics 60 (2021) 89 https://doi.org/10.1364/AO.400508

Team members