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Single-shot flash imaging using a compact soft x-ray microscope


Microscopes extend the ability of our eyes to see objects at micro- and nanoscales. There are applications, however, for which a static image is not sufficient, and thus require information on the dynamics before a process can be understood and controlled. Therefore, the visualization of nanoscale dynamics in real-space can significantly contribute to the understanding of nanoscale processes and to accelerate the development of new nanodevices. Today, there is a need for practical microscopes capable of delivering nanometer spatial resolution and ultrafast temporal resolution in order to readily visualize any arbitrary nanoscale phenomenon. Conventional visible light microscopes can visualize ultrafast dynamics but are inherently limited in spatial resolution to about 200 nm. Alternatively, transmission electron microscopes can routinely provide atomic spatial resolutions of static samples. Probing dynamics is possible using stroboscopic schemes with nanosecond temporal resolution or scanning methods which can obtain femtosecond temporal resolution at the expense of hours-long image acquisition times. Soft x-rays (SXR) microscopes provide the ability to resolve at the nanoscale and at the same time image dynamics with nanosecond to picosecond time resolution. Pioneering work has been carried out using synchrotron illumination that has allowed to study repetitive phenomena in magnetic materials. There are however processes that are statistically reproducible but individually non-recurring that require SXR flash illumination to capture their dynamics. SXR flash imaging requires a large number of photons per pulse to illuminate the sample (about 10E12 photons per pulse). There are two types of SXR sources presently available which offer such high peak brightness: free electron lasers (FEL) and table-top SXR lasers. FELs have been used to probe dynamics using holographic and diffractive imaging configurations. This thesis describes the first demonstration of real-space flash imaging using a compact SXR laser operating at a wavelength of 46.9 nm. A sequence of flash images obtained with the full-field SXR microscope with a spatial resolution of 50 nm and temporal resolution of 1.5 ns captured the interaction dynamics of a rapidly oscillating magnetic tip in close proximity to a magnetized surface. The interaction of the tip and the stray magnetic fields led to changes in the amplitude of the tip oscillation as small as 30 nm. Modeling of the interaction assuming an undamped perturbed harmonic oscillator corroborate the experimental results. The use of compact plasma-based SXR lasers operating at wavelengths down to 10.9 nm will allow to capture flash images and render animations of picosecond phenomena with a few nanometers accuracy on a table-top.


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dynamic imaging
ultrahigh resolution imaging
soft x-rays
single-shot sequential imaging
soft x-ray microscopy
compact EUV sources


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