Depth profiling of marker layers using x-ray waveguide structures

Abstract

It is demonstrated that x-ray waveguide structures can be used for depth profiling of a marker layer inside the guiding layer with an accuracy of better than 0.2 nm. A combination of x-ray fluorescence and x-ray reflectivity measurements can provide detailed information about the structure of the guiding layer. The position and thickness of the marker layer affect different aspects of the angle-dependent x-ray fluorescence pattern, thus making it possible to determine the structure of the marker layer in an unambiguous manner. As an example, effects of swift heavy ion irradiation on a Si/ M / Si trilayer ͑M = Fe, W͒, forming the cavity of the waveguide structure, have been studied. It is found that in accordance with the prediction of thermal spike model, Fe is much more sensitive to swift heavy ion induced modifications as compared to W, even in thin film form. However, a clear evidence of movement of the Fe marker layer towards the surface is observed after irradiation, which cannot be understood in terms of the thermal spike model alone.

Depth resolved structural study of heavy ion induced phase formation in Si/Fe/Si trilayer

“…The base pressure in the chamber was 1.5 × 10 −7 Torr. The Si/Fe/Si trilayer is sandwiched between the two Pt layers in order to form the wave guide structure [4,6]. The Fe layer is enriched in Fe 57 up to 95% in order to get good signal in conversion electron Mössbauer spectroscopy (CEMS).…”

“…Swift heavy ion (SHI) induced mixing in Fe/Si system has been studied extensively in the literature [1][2][3][4]. The observed dependence of mixing efficiency on the mass and energy of bombarding ions can in general be understood in terms of thermal spike model [5].…”

Study of nano-scale diffusion in thin films and multilayers

“…3. Standing waves are generated using total external reflection of x-rays from a layer of high Z material (e.g., Au) [6,7,17]. The incident and the reflected x-ray amplitudes interfere with each other to form standing waves above the surface of totally reflected layer.…”

“…However, some of the x-ray based techniques for depth profiling, e.g., x-ray reflectivity and x-ray fluorescence under standing wave conditions can be conveniently used for studying atomic diffusion at nanometer scale [5,6]. In general, x-rays cannot differentiate between two isotopes of an element, and therefore cannot be used for depth profiling of an isotopic marker layer (as required for studying self-diffusion).…”

Advanced x-ray multilayer waveguide optics

“…C11(c). The detailed fluorescence pattern depends upon the position and thickness of the Co marker layer [93]. Owing to the thinned Co layer and limited step sizes of the instruments, the fluorescence peaks can not match the corresponding resonant modes.…”