**5.1 Experimental setup**

To reach near-ultimate spatial resolution *zp* has to be reduced even further, according to Equations (7) and (20). A sample was composed of carbon nanotubes (CNT) with diameters between 50 and 80 nm and length 10-20 m, placed on a 100 nm thick silicon membrane acting as a support. It was imaged using a table top EUV laser in Gabor's inline configuration as depicted in Fig. 7 and described in more details in (Wachulak et al., 2008b).

Fig. 7. Experimental setup in Gabor's hologram configuration. The EUV laser beam illuminates the object composed of carbon nano-tubes deposited on top of Si membrane.

The thin Si membrane has a transparency of approximately 60% at λ = 46.9 nm 1. The sample was placed approximately *zp* = 2.6 μm away from the Si wafer spin-coated with 120 nm thick layer of PMMA photoresist, resulting in recording NA practically equal to 1. However the limited area of the AFM scan that digitizes the hologram (9.9×9.9 μm2) limits the NA to 0.88. The photoresist was later developed and the hologram stored in the resist was digitized with the AFM and numerically reconstructed using the same Fresnel propagator code. Fig. 8a,c show the holograms digitized with the AFM. The corresponding numerical reconstructions are shown in Fig. 8b,d. The CNTs are clearly visible as white lines in a black background.

The spatial resolution in the reconstructed image was found applying the knife-edge method. It is based on measuring 10-90% rise of the intensity in the line-cuts through the image. Two examples of such line-cuts depicted in Fig. 9a,b were taken in regions indicated in Fig. 8b,d. These cuts were realized in region where a "plateau" in the maximum and minimum intensities was clearly reached, to recreate the knife-edge resolution test. The measurements yielded the spatial resolution of ~46 nm. A mean value of resolution was found in similar cuts realized in different areas in the reconstructed images resulting in the statistical resolution of 45.8±1.9 nm, where error is assigned by a standard deviation spread in the measurements (Wachulak et al., 2008b).

<sup>1</sup> *from CXRO database, "http://www-cxro.lbl.gov/".* 

To reach near-ultimate spatial resolution *zp* has to be reduced even further, according to Equations (7) and (20). A sample was composed of carbon nanotubes (CNT) with diameters between 50 and 80 nm and length 10-20 m, placed on a 100 nm thick silicon membrane acting as a support. It was imaged using a table top EUV laser in Gabor's inline configuration as depicted in Fig. 7 and described in more details in (Wachulak et al.,

Fig. 7. Experimental setup in Gabor's hologram configuration. The EUV laser beam illuminates the object composed of carbon nano-tubes deposited on top of Si membrane.

The thin Si membrane has a transparency of approximately 60% at λ = 46.9 nm 1. The sample was placed approximately *zp* = 2.6 μm away from the Si wafer spin-coated with 120 nm thick layer of PMMA photoresist, resulting in recording NA practically equal to 1. However the limited area of the AFM scan that digitizes the hologram (9.9×9.9 μm2) limits the NA to 0.88. The photoresist was later developed and the hologram stored in the resist was digitized with the AFM and numerically reconstructed using the same Fresnel propagator code. Fig. 8a,c show the holograms digitized with the AFM. The corresponding numerical reconstructions are shown in Fig. 8b,d. The CNTs are clearly visible as white lines in a black

The spatial resolution in the reconstructed image was found applying the knife-edge method. It is based on measuring 10-90% rise of the intensity in the line-cuts through the image. Two examples of such line-cuts depicted in Fig. 9a,b were taken in regions indicated in Fig. 8b,d. These cuts were realized in region where a "plateau" in the maximum and minimum intensities was clearly reached, to recreate the knife-edge resolution test. The measurements yielded the spatial resolution of ~46 nm. A mean value of resolution was found in similar cuts realized in different areas in the reconstructed images resulting in the statistical resolution of 45.8±1.9 nm, where error is assigned by a standard deviation spread

**5. Wavelength resolution holography** 

**5.1 Experimental setup** 

2008b).

background.

in the measurements (Wachulak et al., 2008b).

<sup>1</sup> *from CXRO database, "http://www-cxro.lbl.gov/".* 

Fig. 8. a,c) Holograms and b,d) reconstructed images of 50-80 nm diameter carbon nanotubes. The holograms were obtained by scanning the photoresist surface with the AFM. Knife-edge test was applied to estimate the resolution of the reconstructed image in b,d).

Fig. 9. The intensity lineouts through the reconstructions indicating a 10-90% intensity modulation over approximately 4.5 pixels. Figure a,b) corresponds to the reconstructed images in Fig. 8b,d) respectively. A mean value of multiple cuts obtained at different locations yielded the spatial resolution of 45.8±1.9 nm.
