## 2 Materials and Methods  
### The EUV and SXR microscopes  
Soft X-ray contact microscope and the full-field EUV/SXR microscopes are schematically depicted in Figure 1b-d, respectively. The sources for those microscopes are based on a compact Nd:YAG laser, \(\lambda\) = 1064 nm, 0.5-0.7 J pulse energy, 3 ns pulse duration, and 1-10 Hz repetition rate. The laser beam is focused onto a double-stream gas puff target, which is schematically depicted in Figure 1a.  
The target is produced by an electromagnetic valve with double radially-symmetric nozzles. Laser pulses irradiate the gaseous target producing plasma. The plasma emits radiation in various spectral ranges, including the EUV and SXR regions of electromagnetic spectrum. Depending on the spectral range and on the type of the microscope, the gas puff target source was optimized for efficient emission in the \"water window\" (both quasi-monochromatic for the SXR full-field microscope and broadband for contact SXR microscope) and the EUV spectral range, using spectral narrowing with thin metal filters. A nitrogen plasma radiation, filtered with a Ti foil, provides \(\lambda\) = 2.88 nm wavelength radiation and an Ar plasma emission, filtered with Mo/Si multilayer mirror and Zr filter provides radiation at \(\lambda\) = 13.84 nm. However, for the argon plasma, if a silicon nitride filter is used, it provides emission from 2.8 to 4 nm with much larger number of photons than in case of nitrogen plasma, suitable for contact microscopy. Such sources were employed for SXR and EUV experiments, respectively. The gas pressures, nozzle position in respect to the laser focus, and valve timing in respect to the laser pulse were optimized in order to maximize the photon flux at the sample plane. The inner nozzle injects a small amount of working gas (high \(Z\) gas--N\({}_{2}\) at 8 bar, in case of SXR full-field microscope, and Ar, at 10 bar, in case of the EUV full-field microscope and contact SXR microscope), while the outer nozzle injects an outer gas (low \(Z\) gas--He, with a pressure of 6 bar), to narrow down the flow of the working gas, reducing its density gradient along the nozzle axis. Such an approach can obtain higher target density by confining the target gas flow and, in turn, allows for higher photon yield in the EUV/SXR region. Such radiation is then focused using condenser optics and illuminates the sample, Figure 1c,d, located in a second focal point of a condenser in the case of full-field microscopes. Depending on the type of microscope, plasma radiation is collected and focused by a different condenser and filter, and images of the objects are obtained with different zone plates using a back-illuminated charge-coupled device (CCD) camera. In the case of contact SXR microscope the scheme is much simpler, as can be seen in the case of contact SXR microscope.  
Figure 1: (**a**) Scheme of the double stream gas puff target employed in laser-plasma EUV/SXR sources, (**b**) scheme of the contact SXR microscope, (**c**) scheme of the SXR full-field microscope, and (**d**) scheme of the EUV full-field microscope employing off-axis condenser geometry.  
seen in Figure 1b, because radiation from the plasma is transmitted through a 200 nm thick Si\({}_{3}\)N\({}_{4}\) filter and illuminates the sample directly to form its imprint in the surface of the photoresist. In the following paragraphs, the systems will be described in more detail.