A Compact “Water Window” Microscope with 60 nm Spatial Resolution for Applications in Biology and Nanotechnology

Abstract

Short illumination wavelength allows an extension of the diffraction limit toward nanometer scale; thus, improving spatial resolution in optical systems. Soft X-ray (SXR) radiation, from "water window" spectral range, λ=2.3-4.4 nm wavelength, which is particularly suitable for biological imaging due to natural optical contrast provides better spatial resolution than one obtained with visible light microscopes. The high contrast in the "water window" is obtained because of selective radiation absorption by carbon and water, which are constituents of the biological samples. The development of SXR microscopes permits the visualization of features on the nanometer scale, but often with a tradeoff, which can be seen between the exposure time and the size and complexity of the microscopes. Thus, herein, we present a desk-top system, which overcomes the already mentioned limitations and is capable of resolving 60 nm features with very short exposure time. Even though the system is in its initial stage of development, we present different applications of the system for biology and nanotechnology. Construction of the microscope with recently acquired images of various samples will be presented and discussed. Such a high resolution imaging system represents an interesting solution for biomedical, material science, and nanotechnology applications.

Development and optimization of a “water window” microscope based on a gas-puff target laser-produced plasma source

“…The system is compact in size and makes possible wider collaboration in a multidisciplinary context with biologists, chemists, and scientists from other disciplines locally, in the university laboratories or companies. Moreover, such system offers higher spatial resolution to the visible light microscopes [17], [22] and do not require sample preparation like SEM microscopes. Although the spatial resolution achieved cannot compete with the SEM, it has to be EPJ Web of Conferences 167, 03002 (2018) https://doi.org/10.1051/epjconf/201816703002 PPLA 2017 noted that the SXR microscope still operates using photons instead of electrons.…”

Plasma characterization of the gas-puff target source dedicated for soft X-ray microscopy using SiC detectors

“…Figure 4 shows typical emission spectrum from nitrogen plasma in the 'water window' range (dashed line), generated by focused Nd:YAG laser pulse interacting with nitrogen/helium gas-puff target. The plot shows the H-like nitrogen line ( = 2.48 nm), attenuated by 200 nm thick Ti fi lter (dash-dotted line), and the He-like nitrogen line at  = 2.88 nm wavelength (solid line) used for imaging with the SXR microscope [18].…”

Nanoimaging using soft X-ray and EUV laser-plasma sources

“…The geometrical magnification of the system was ~220x. It was already demonstrated that such system is capable to achieve a half-pitch spatial resolution of ~60nm [24]. More details about this work can be found in [25].…”