A nanometer axial resolution X-ray coherence tomography with a broadband SXR radiation emitted from a compact laser plasma double-stream gas-puff target source

摘要

The optical coherence tomography (OCT), typically used in the visible wavelength range, due to relatively longwavelength is limited by the axial resolution to approximately a few hundreds of nanometers to a micron. Visible light isalso incapable of resolving multilayered structures of tens of nanometers periods. Thus, the extension of the OCT toshorter wavelengths, such as the extreme ultraviolet (EUV) and soft X-ray (SXR), in the so-called X-ray coherencetomography (XCT), allows mitigating those problems. We present a nanometer resolution XCT using broadband SXRradiation with 2 nm axial resolution using a compact laser plasma soft X-ray source. The laser-produced Kr/He plasmawas formed by the interaction of nanosecond laser pulses with a gaseous target in a double stream gas puff targetapproach, emitting 2 to 5 nm wavelength broadband radiation. The coherence parameters of the SXR radiation allowedfor the OCT measurements of a bulk multilayer structure composed of Mo/Si multilayers with 10 nm period, with anaxial resolution of about 2 nm, the interface position accuracy of sub-nm and detection of multilayer interfaces up to adepth of about 100 nm. The experimental data were compared to the OCT simulations.