EXCIMER LASERS LABORATORY
2000-2001 ANNUAL REPORT
      Introduction  up

The term excimer laser covers a family of laser systems that emit pulses in the ultraviolet (UV) spectrum with high efficiency. The good reliability of the performance of commercial excimer lasers promoted their widespread use in many applications requiring intense UV light, e.g., photolithography, micro-electronics, material processing, surface treatments, micromachining, photo-chemistry, remote sensing , corneal-corrective-surgery, X-ray emission by laser-plasma. However, commercial excimer lasers are not suitable for important applications, such as large area material processing and laser beam propagation down optical fibres. This is due, respectively, to the limited (< 5 cm2) beam size (which in turn limits the output energy) and to the short (< 30 ns) laser pulsewidth typical of commercial excimer laser systems. These limitations were addressed at the ENEA Frascati back in the late seventies, when work started on designing and constructing XeCl lasers with large active medium, high output energy and long pulsewidth.
During the years 2000 - 2001, the work at the ENEA Frascati Excimer Laboratory was mainly focused on constructing the first Italian industrial XeCl laser (in the frame of the European Project FOTO, aimed at achieving high-mobility thin-film-transistors by laser-induced a-Si recrystallisation) and on using the XeCl laser facility Hercules to drive a plasma X-ray source for extreme ultraviolet microlithography and high-resolution spectroscopy. In addition, work was done on the design and test of a novel beam homogenizer (ENEA patent pending), on a novel laser-plasma debris mitigation system (ENEA patent pending), on developing and testing the first European capillary-discharge soft X-ray laser, and on X-ray contact microscopy and radiography.
 

The project FOTO  up

The European project FOTO aims at the realisation of a clean room for the laser annealing of amorphous silicon (a-Si) as a first step to finally achieve high-mobility thin-film-transistors (TFTs) and/or high-efficiency photovoltaic cells. This project involves many partners: among them, we had a close collaboration with the ERG FORI Division (ENEA Portici), CNR IESS (Rome) and the SME El.En. S.p.A. (Calenzano, Florence).

Hercules-L, an industrial prototype of excimer laser
The new XeCl excimer laser, named “Hercules-L”, is a commercial version of the laser facility Hercules described in the 1998 Annual Report of the ENEA Applied Physics Division. The main technical improvements of Hercules-L vs. Hercules can be summarised as follows:

During 2000-2001, Hercules-L was installed at ENEA Portici (see Figure 1) and the laser performance were optimised to the main irradiation processes of the ENEA Portici Lab, namely the annealing of a-Si films on both glass and plastic substrates. Table 1 summarises the main Hercules-L laser performance achieved.
We point out that Hercules-L is the first industrial prototype of large-volume excimer laser made in Italy, and it is one of the highest output energy excimer laser commercially available world-wide.
 
 
Hercules L Figure 1. Hercules-L installed at ENEA Portici. The overall laser system dimensions are h x w x l = (2 x 1.5 x 2.5) m3

 

Table 1. Main features of the industrial prototype Hercules L.

Active medium
XeCl
Active medium pressure
4.5 bar
Emitted wavelength
308 nm
Preionisation
  X-rays (80 keV) 
Gas flow
Axial, 25 m/s
Discharge voltage
50 kV
FWHM laser pulsewidth 
100-140 ns
Max output energy
 12 J
Peak power (typical)
82 MW 
Maximum repetition rate
10 Hz
  Average power (in bursts of 100 shots) 
100 W
Near-field laser beam size
7 cm x 10 cm
Shot-to-shot stability
 > 97%

A novel laser beam homogeniser
A good spatial uniformity of the laser beam incident onto the a-Si panel is a preliminary condition to ensure a good uniformity of the poly-Si grain size and of the electric properties of TFTs. A convenient way to make uniform the energy distribution of a beam is using a suitable optical beam homogeniser. The basic principle of the beam homogeniser is using cylindrical lenses to divide the incoming beam in a 2-D matrix of secondary beamlets that overlap in the focal plane of the condenser lens. In this way, local spatial fluctuations of the beam energy are averaged due to the overlap of different portions of the input beam. Figure 2 shows the calculated beam path of a conventional homogeniser acting along one direction, with four secondary beamlets.
During 2000, we have filed a patent on a novel homogeniser optical system, schematised in Figure 3. Unlike conventional homogenisers, the ENEA Homogeniser uses up to three equivalent optical elements for each of the two transverse directions, thus allowing a continuous variation of the beam size on the focal plane along both transverse directions separately, for any input beam size. Unlike conventional homogenisers, the ENEA Homogeniser may use arrays possibly made by lenses with different size to achieve a better reduction of local intensity fluctuations when they are very different from the average intensity fluctuations. ENEA’s Homogeniser technology (patent pending) includes a proprietary software to design the optimum optical system to achieve the wished output beam performance (once known the input beam characteristics), and to know the modification of the beam shape on the focal plane when changing the position of each optical element. This software is written in Visual C++ and runs on MS Windows 95/98. It makes use of either a geometrical optic approach or a ray-tracing technique in order to simulate the path of the light beam, depending on the requirements of the user/designer. The simulated results are in excellent agreement with the experimental ones.
 
 

Figure 2.  One-dimensional scheme of a conventional beam homogeniser. The laser beam, coming on the left, is splitted in four beamlets that are overlapped in the focal plane by a condenser lens.
Figure 3.  One-dimensional scheme of the ENEA Homogeniser. The laser beam, coming on the left, is splitted by the lens array in four beamlets, which are overlapped in the focal plane by a condenser lens and a zoom lens.

Table 2 is a partial specification sheet of the ENEA Homogeniser. Unlike commercial  systems, ENEA’s Homogeniser can be easily adjusted to a broad range of custom requirements.

Table 2. Specifications of the ENEA Homogeniser parameters.

PARAMETER
SPECIFICATION
EXPERIMENTAL TEST
Wavelength Any wavelength, from Vacuum Ultraviolet to Infrared Visible (HeNe) and UV (XeCl)
Input beam size No beam size limits Up to 5 cm x 10 cm
Input beam profile Gaussian or not Gaussian Not Gaussian
Beam energy The maximum energy depends on beam size and beam fluence Up to 8 J @ 308nm
Beam fluence / power density The maximum energy/power density depends on coating/optics damage threshold as given by manufacturers
Zoom factor The zoom factor is given by the ratio maximum to minimum beam size. Theoretically, the maximum zoom factor along one side can be as large as one thousand Up to 10
Homogenizer length Depends on the input beam size and on the zoom factor required  From 0.4 m to 1.7 m
Beam Size at Image Depends on the input beam size and on the zoom factor required From 0.5cm x 0.5cm to 5cm x 5cm. No problems for achieving larger or smaller sizes
Attenuation The minimum attenuation depends on the beam divergence and on the quality of coatings/optics. It can be increased by a manual attenuator 20% @ 308nm (coating not optimised, laser beam not collimated)

The ENEA invention is suitable for any application that requires light beams with a uniform spatial energy density distribution, a sharp spatial steepness and a variable spot size and/or a variable energy density value. Typical examples are thermal and ablative treatments of materials by laser radiation (surface cleaning, selective material removal, drilling, metal hardening, corrective eye surgery, annealing of silicon, photoresist irradiation, chipmaking, etc.) as well as high-power fiber injection issues.
In particular, the ENEA’s Homogeniser Optical System is useful in the following cases:
1. irradiation processes when the optimum energy density and/or spot size of the irradiation (illumination) process are not known in advance. Operators can vary the output spot size and/or energy density of the homogenised beam until the optimal working point is reached - all without making the expensive and time-consuming equipment adjustments necessary with existing beam-handling systems.
2. homogenisation of light beams having such strong local intensity fluctuations that the average homogeneity value is much different of the local homogeneity value.
Thanks to the licensing agreement between ENEA and Info & Tech S.p.A. (via Milazzo, 8, 33100 Udine Italy, fax: +39 0438 402415; and via Teognide, 24, 00124 Roma, Italy; tel +39 06 52364770; fax +39 06 52364778; www.infoetech.com E-mail: mail.roma@infoetech.com) the ENEA’s Homogeniser technology is commercially available.
Figure 4 shows the first prototype of the ENEA Homogeniser System after it was installed at ENEA Portici. This prototype is optimised to make spatially homogeneous the laser beam emitted by Hercules-L, with a 1-D zoom factor up to seven.

ENEA homogenizer installed at Portici (Naples) Figure 4. First prototype of the ENEA’s homogeniser, installed at ENEA Portici. It is used to make spatially homogeneous the 10cm x 7cm laser beam emitted by Hercules-L, with a linear zoom factor up to seven along the vertical direction.

Extreme Ultraviolet light source for microlithography  up

Recently, the research on the Extreme Ultra-Violet Lithography (EUVL) has reached a strategic importance for microchips fabrication in the microelectronic industry. In fact, EUVL potentially allows a technological jump, leading the spatial resolution on dense lines from the current value of 180 nm to values as low as 70 nm (expected within 2005) and 30 nm (expected within 2010). This can be obtained by using radiation at about 14 nm (in the EUV spectrum, i.e. photons with energies in the range 20 < hn < 300 eV) rather than at 248 nm or 193 nm today used for the projection of the electric circuit from the mask to the silicon wafer. The use of EUV radiation at 14 nm implies the use of multilayer mirrors rather than lenses for the mask imaging.
In this frame, the Excimer Laboratory at ENEA Frascati contributed to submit three proposals for the development of a clean, high-efficiency EUV laser plasma source, respectively in the frame of two National Projects (FISR and FIRB) and of one European Project (EUNETE).
In the meantime, using our laser-plasma EUV source (detailed in the Annual Report 1999 of the ENEA Applied Physics Division), we carried out preliminary experiments in co-operation with L'Aquila University and ENEA FIS TEO. In particular, our effort was devoted to reduce the amount of debris (ions and clusters) emitted by our plasma-source. This is a very important task since a main concern on EUVL systems is the life-time of the expensive mirrors, limited by debris surface contamination. By using a novel Debris Mitigation System (ENEA patent pending), we have substantially reduced the debris flux by more than two orders of magnitude. The Debris Mitigation System (DMS), schematized in Fig. 5, is based on rotating apertures in an atmosphere of low-pressure krypton. The dramatic filtering effect of the DMS on copper debris emitted by the ENEA laser-plasma source is shown in Fig. 6.

The ENEA Debris Mitigation System Figure 5: Schematic of the DMS (ENEA patent pending). When the holes of the rotating disks overlap, the laser-plasma EUV source is fired. The EUV photons pass through the holes and reach the condenser mirror, while the debris, slowed down by krypton, are finally stopped by the disks, which have turned in the meantime.

 
Debris on a glass (without DMS)
Debris on a glass (with DMS)
a)  without DMS   (OD=0.6)
b)  with DMS   (OD=0.002)
Figure 6:  Copper debris deposited on a glass plate exposed to 500 shots without (a) and with (b) the DMS. White bright bowls are cluster debris while the dark areas are layers formed by deposition of ions. The optical densities (OD) of the glasses shown in (a) and (b), compared with the non-exposed glass, are 0.6 and 0.002, respectively.



High-resolution spectroscopy and atomic physics in the 1 keV spectral region  up

This activity was done in co-operation with the MISDC of VNIIFTRI Institute of Moscow, using spectrometers based on a proprietary technology of spherically bent crystals developed at MISDC and the ENEA Frascati laser-plasma soft X-rays source, whose emission was tuned around 1000 eV. On the basis of experimental and theoretical investigations we demonstrated for the first time that in cold and optically thick laser produced plasmas, created near the target surface, the capture into the He-like ground state 1s2 + e à 1s3 l n l ' is negligible for the line formation and that the observed high intensity He?-Rydberg satellite lines are correlated with highly populated He-like excited states  1s2 l. X-ray emission spectra simultaneously measured with high spectral (l/Dl = 10,000) and spatial resolution (Dx = 10 mm) provided a direct verification of the proposed excitation mechanism. Atomic data calculations for all configurations with n = (3 – 6) have been carried out and employed in spectral modelling, obtaining an excellent agreement with experiments, as shown in Fig. 7. Successful cross-checks with the spectral interval near the Hea-line have been demonstrated.
 

Figure 7: The Mg spectrum (emitted by the ENEA laser plasma source driven by Hercules laser, 10 ns - 1.3 J) compared to the computed MARIA-spectrum fitting the Heb-line and its dielectronic satellites 
1s2l3l', 1s3l3l', 1s3l4l' and 1s3l5l'.
The data are: ne = 8*1021 cm-3, kTe = 100 eV, Leff = 15 mm, V = 2*105 cm/s. The labels "1, 2, 3, 4" indicate the density-sensitive transitions for the 1s2l3l' - 1s22l satellites

Contact micro-radiography of leaves by X-ray laser plasma source  up

We carried out contact micro-radiography for imaging of leaves using different target materials as laser-plasma sources of soft X-rays (i.e. photons with energies in the range  300< hn <8000 eV). The aim of this study (done in collaboration with the Biology Lab FIS-LAS at ENEA Frascati, L’Aquila University and the Engineering Institute of Tor Vergata University) is to demonstrate the possibility to detect a chemical element in the leaf structures, by using the same chemical element as target of the laser-plasma source.
Iron, magnesium and copper targets were chosen for their own importance in the leaf structure. In fact, magnesium activates many molecules involved in respiration, RNA and DNA synthesis; it is also an important component of the porphyrin structure of chlorophyll. Iron is a fundamental constituent of molecules like cytochrome, involved in the electron transport chain during photosynthesis. Copper is involved in the activity of some electron carriers (as plastocyanin).
The soft X-rays images of leaves give a natural high contrast of the leaf structure, as shown in Fig. 8. In order to increase the contrast inside the leaf structure, some leaves were treated with a solution of copper sulfate and compared with untreated leaves. The preliminary results suggest that the copper sulfate mainly concentrates in bowls having a size of 50 mm (probably corresponding to the stomata of the leaves), as shown in Fig. 9.
The results show differences of imaging treated leaf compared to untreated leaves and indicate that this technique could be useful to predict and to find an illness of a plant due to the lack of some elements like iron and magnesium, and it could help in detecting the real intake of elemental pollutants by a plant for phytoremediation of the ground.

 a) with visible light
b) with soft X-rays 
Figure 8: Comparison of a hedera leaf observed in transmission at visible light and at soft X-rays (1000 eV). Note that in the X-ray image the internal structure is visible everywhere (even in the dark green areas of the leaf) with a higher contrast compared with the visible light image. The height of both images is 35 mm.

 
a) 
b) 
Figure 9: Soft X-ray micro-radiography of Viola x wittrockiens leaves. Detail of a non-treated leaf (a) and of a leaf treated with 5% Cu sulfate for 24 hours before being exposed to soft X-rays emitted by Cu targets (b). The contrast is much higher in the treated leaf and the 50-mm-wide bowls opaque to X-rays (probably corresponding to stomata) are much more evident. The spatial resolution is limited to about 5 mm by the film emulsion grains, which make the image a bit noisy.

Luminescent patterns after EUV irradiation of LiF crystals  up

The EUV and soft-X-rays emitted by our laser-plasma source driven by the laser facility Hercules can generate permanent color-centers in LiF crystals and LiF films, more efficiently than conventional X-rays and on a much thinner layer. This means that high-resolution (sub-mm) luminescent patterns can be obtained in LiF crystals/films by means of EUV-lithographic techniques. This new application of soft X-rays potentially allows producing miniaturised active optical devices, compact photonic and optoelectronic devices, etc. This is one of the most fascinating field in the nano-technology: in fact, visible solid state sources emitting in the visible can be used in CD readers, laser printers, displays and optical memory units.
Recently, we have carried out preliminary experiments in collaboration with the Solid State Laboratory (ENEA Frascati), the Thin Films Laboratory (ENEA Casaccia), and the MISDC of VNIIFTRI Inst. of Moscow, for the generation of luminescent patters in LiF crystals / films. We made a first attempt to produce patterns by the "contact mode" lithographic technique, that is by placing a mask (e.g., a grid) as close as possible to the LiF crystal/film. This technique exploits the extremely small dimensions (< 100 mm) of the laser-plasma sources, which allows a very small penumbra blurring. By exposing a LiF crystal to 1000 shots at 10 cm from the ENEA laser-plasma source we obtained intense luminescent patterns over a large area (1 cm2) and with a high spatial resolution (1 mm), as shown in Fig. 10. Further experiments are scheduled by 2002 and 2003 in order to reach a sub-micron resolution.

Luminescence emitted by a LiF crystal after EUV exposure

Figure 10: Luminescence yellow light emitted by the surface of a LiF crystal after irradiation of 1000 shots of EUV radiation, masked by two grids placed in contact with the crystal. The luminescence (related to the presence of color-centers in the crystal structure) is emitted only by the areas exposed to the EUV radiation. The depth of the luminescent patterns in the LiF crystal is just 50 nm, while the transverse spatial resolution is less than 1 mm
 

Capillary discharge soft X-ray laser  up

The Excimer Laser Laboratory has contributed to the development and test of a capillary discharge soft X-ray laser, installed at L'Aquila University, based on the amplification of the 3p-3s transition of the Ne-like argon ions. The laser active medium is 0.3 mbar of Ar gas, contained in a 15-cm-long, 3-mm-diameter tube, and it is heated by a 30-kA fast current pulse (see Figs. 11 and 12). During the current rise-time, the column of hot gas is pinched by the current magnetic field down to a diameter of 0.5 mm (see Fig. 12), where the temperature rises to 106 K and the ionisation state of Ar atoms reaches the Ne-like level. Soft X-rays (mainly in the EUV spectral region) are emitted by spontaneous emission during the whole 150 ns current pulsewidth, but the lasing effect at 46.9 nm is obtained only at the maximum plasma compression (corresponding to the highest plasma temperature), as shown in Fig. 13. The laser pulse lasts only 1.5 ns.
It is worth noticing that this is the first successful capillary-discharge soft X-ray laser emission in Europe since the first discharge-pumped X-ray laser developed by the group of J. Rocca (Colorado University, USA) in 1994.

High voltage discharge in an Argon capillary tube Figure 11: Photo of the Ar plasma column, inside a Perspex capillary tube, when heated by a high current pulse. Visible, UV, VUV end EUV radiation are emitted by spontaneous emission. Laser radiation at 46.7 nm is only emitted axially at the end of the 15-cm-long amplification path.
Figure 12: Radius of the plasma column (solid line) and current intensity (dashed line) as calculated by a magneto-hydro-dynamic code.
Figure 13: Oscilloscope trace of the X-Ray Detector (XRD) signal (solid line) and of the Rogowski current probe (dashed line). The XRD is placed 1 m away the capillary discharge exit.

Contact X-ray microscopy

The contact X-ray microscopy technique allows to image one or few biological samples in vivo by exposing them to plasma-laser soft X-rays in the water-window spectrum (284 eV <  h < 532 eV, between the carbon and the oxygen absorption K-edge). In this spectral range proteins (containing carbon) have a much larger absorption coefficient than water (containing oxygen), so that high contrast transmission images of living biological specimen can be obtained on a suitable resist put in contact with the specimen. The small wavelength of soft X-rays allows a higher resolution (typically, better than 100 nm) than that of optical microscopes, while their small absorption in water-rich tissues allows to image relatively thick samples (1 mm - 10 mm), like whole cells.
This activity started many years ago in collaboration with the University of L'Aquila, Dept. of Physics and Dept. of Biology (see the 1994 and 1998 Annual Reports of the ENEA Applied Physics Division). After imaging alga chlamydomonas, red blood corpuscles and bacteria leptolyngbya, we have recently imaged a wine saccharomycetus shown in Fig. 14.
In the next future we are planning a change in the microscopy technique from "contact mode" to "projection mode" using Fresnel zone-plate lenses and a CCD camera. This change should allow a spatial resolution better than 100 nm.
 

Figure 14: Contact X-ray microscopy image of a wine saccharomycetus. Both horizontal and vertical scales are in mm.

 

PAPERS   up

REPORTS

1) S. Bollanti, P. Di Lazzaro, D. Murra, A. Imparato, C. Privato, R. Carluccio, G. Fortunato, L. Mariucci, A. Pecora: “Cristallizzazione di silicio amorfo via laser: rapporto degli esperimenti a Frascati (Progetto FOTO)” RT/INN/00/12 (2000).

2) P. Di Lazzaro: “Luce ultravioletta per il finissaggio di tessuti” RT/INN/01/154 (2001).
 

BOOKS

1) P. Di Lazzaro, S. Bollanti, D. Murra, C.E. Zheng: “Improved Beam Quality Excimer Lasers: a Filtering Resonator Study” Chapter 5 in “Filtering Resonators”, S.K. Dixit editor (Huntington, N.Y. Nova Science publisher, 2001).
 

PUBLICATIONS

1) P. Fournier, H. Haseroth, H. Kugler, N. Lisi, R. Scrivens, F. Varela Rodriguez, P. Di Lazzaro, F. Flora, S. Duesterer, R. Sauerbrey, H. Schillinger, W. Theobald, L. Veisz, J. W. Tisch, R. A. Smith: Novel laser ion sources, Rev. Sci. Instrum. 71, 1405 (2000).

2) F. Rosmej, U. Funk, M. Geissel, D. Hoffmann, A. Tauschwitz, A. Faenov, T. Pikuz, I. Skobolev, F. Flora, S. Bollanti, P. Di Lazzaro, T. Letardi, L. Palladino, A. Reale, G. Tomassetti, A. Scafati, L. Reale, T. Auguste, P. Oliveira, S. Hulin, P. Monot, D. Umstadter, N. Shilkin: X-ray radiation from ions with K-shell vacancies, J. Quant. Spectrosc. Radiat. Transfer 65, 477 (2000).

3) E. Biemont, A. I. Magunov, V. M. Dyakin, A. Faenov, T. A. Pikuz, I. Yu. Skobelev, A. Osterheld, W. H. Goldstein, F. Flora, P. Di Lazzaro, S. Bollanti, N. Lisi, T. Letardi, A. Reale, L. Palladino, D. Batani, A. Mauri, A. Scafati, L. Reale: Measurement of the ground state ionization energy and wavelengths for 2l-nl’ transitions of Ni XIX (n=4-15) and Ge XXIII (n=7-9), J. Phys. B: At. Mol. Opt. Phys. 33, 2153 (2000).

4) J. Abdallah, I. Skobolev, A. Faenov, A. I. Magunov, T. Pikuz, F. Flora, S. Bollanti, P. Di Lazzaro, T. Letardi, E. Burattini, A. Grilli, A. Reale, L. Palladino, G. Tomassetti, A. Scafati, L. Reale: Spectra of multiply charged hollow ions in the plasma produced by a short-wavelength nanosecond laser, Quantum Electronics 30, 694 (2000).

5) S. Bollanti, T. Letardi, C.E. Zheng: Flight range of the particulate in a laser-plasma generated soft X-ray chamber, Appl. Phys. A71, 255 (2000).

6) S. Kukhlevsky, F. Flora, A. Marinai, L.Palladino, A. Reale, G. Tomassetti, L. Kozma: Diffraction of X-ray beams in capillary optics,  Appl. Opt. 39, 1059 (2000).

7) S. Kukhlevsky, F. Flora, A. Marinai, G. Nytray, L. Kozma, A. Ritucci, L.Palladino, A. Reale, G. Tomassetti: Wave-optics treatment of X-ray passing through tapered capillary guides, X-rays spectr. 29, 354 (2000).

8) S.V. Kukhlevsky, F. Flora, A. Marinai, G. Nytray, A. Ritucci, L. Palladino, A. Reale, G. Tomassetti: "Diffraction of x-ray beams in capillary waveguides", Nucl. Instr. Meth. B, 168, 276-282, 2000.

9) Batani D, Botto C, Bortolotto F, Masini A, Bernardinello A, Moret M, Milani M, Eidmann K, Poletti G, Cotelli F, Donin CLL, Piccoli S, Stead A, Ford T, Marranca A, Flora F, Palladino L, Reale L: "Contact X-ray Microscopy using the Asterix Laser Source", Phys. Medica, Vol. 16 (2), 49-55,  2000.

10) Kukhlevsky S, Kaiser J, Reale A, Tomassetti G, Palladino L, Ritucci A, Limongi T, Flora F, Mezi L: "Capillary discharge experiment for collisional excitation soft X-ray laser", J. Phys IV, 11, 583-586, 2001.

11) S. Bollanti, F. Bonfigli, P. Di Lazzaro, F. Flora, G. Giordano, T. Letardi, D. Murra, G. Schina, C. E. Zheng: “Pulsed X-ray generator for commercial gas lasers” Rev. Sci. Instrum. 72, 3983 (2001).

12)  P. Di Lazzaro: “Finissaggio di tessuti sintetici con luce ultravioletta” Innovare 2, 32 (2001).

13) Pikuz T, Faenov AY, Fraenkel M, Zigler A, Flora F, Bollanti S, Di Lazzaro P, Letardi T, Grilli A, Palladino L, Tomassetti G, Reale A, Reale L, Scafati A, Limongi T, Bonfigli F, Alainelli L, Del Rio MS: "Shadow monochromatic backlighting: Large-field high resolution X-ray shadowgraphy with improved spectral tunability", Laser Part. Beams, 19, 285-293, 2001.

14) Flora F, Mezi L, Zheng CE, Bonfigli F: "Krypton as stopper for ions and small debris in laser plasma sources", Europhys. Lett.  56, 676-682, 2001.

15) Kukhlevsky SV, Kaiser J, Ritucci A, Tomassetti G, Reale A, Palladino L, Kozma IZ, Flora F, Mezi L, Samek O, Liska M: "Study of plasma evolution in argon-filled capillary Z-pinch devoted to x-ray  production", Plasma Sources Sci. T, 10 567-572, 2001.

16) Bollanti S, Bonfigli F, Di Lazzaro P, Faenov A, Flora F, Giordano G, Letardi T, Limongi T, Mezi L, Murra D, Pikuz T, Palladino L, Reale A, Reale L, Ritucci A, Scafati A, Tomassetti G, Vitali A, Zheng CE: "Applications of plasmas produced with the Hercules L excimer laser", J. de Phys. IV, Vol. 11 (PR7), pp. 133-134, 2001.
 

CONFERENCES PROCEEDINGS

1) P. Di Lazzaro, S. Bollanti, F. Bonfigli, F. Flora, T. Letardi, D. Murra: Beam quality of an XeCl laser vs. the repetition rate, in Advanced High-Power Lasers, M. Osinski, H. Powell, K. Toyoda, Eds., SPIE vol. 3889 (2000) pp. 379 – 387.

2) T. Letardi, A. Baldesi, S. Bollanti, F. Bonfigli, P. Di Lazzaro, F. Flora, G. Giordano, D. Murra, G. Schina, C.E. Zheng: Industrial large aperture XeCl laser for surface processing, in High-Power Lasers in Manufacturing, X. Cheng, T. Fujioka, A. Matsunawa, Eds., SPIE vol. 3888 (2000) pp. 587 – 597.

3) D. Murra, S. Bollanti, F. Bonfigli, D. Della Sala, P. Di Lazzaro, T. Letardi: Experimental results on silicon annealing by a long pulse XeCl laser, in ALT ’99, Int. Conf. on Advanced Laser Technologies, V.I. Pustovoy, V.I. Konov, Eds., Proc. SPIE vol. 4070 (2000) pp. 345 - 350.

4) F. Rosmej, D. Hoffmann, W. Suss, M. Geissel, A. Faenov, I. Skobolev, T. Pikuz, R. Bock, T. Letardi, F. Flora, S. Bollanti, P. Di Lazzaro, Yu. Satov, V. Roerich, A. Reale, T. Auguste, P. Oliveira, S. Hulin, P. Monot, B. Sharkov: Investigation of fast ions and hot electrons in laser produced plasmas by means of high resolution spectroscopy, in Inertial Fusion Sciences and Applications: State of the art 1999, C. Labaune, W. Hogan, K. Tanaka Eds., (2000) pp. 545 – 550.

5) S. Bollanti, F. Bonfigli, P. Di Lazzaro, A. Faenov, F. Flora, G. Giordano, T. Letardi, T. Limongi, L. Mezi, D. Murra, T. Pikuz, L. Palladino, A. Reale, L. Reale, A. Ritucci, A. Scafati, G. Tomassetti, A. Vitali and C.E. Zheng: Applications des plasmas produits par le laser à excimères HERCULES-L: du recuit du silicium à la lithographie par rayons X, Proc. of UVX 2000 Conference (Porquerolles, France 2000).

6) D. Murra, S. Bollanti, P. Di Lazzaro, C.E. Zheng: Peak power density of focused laser beams vs. different beam quality factors, in Laser Beam and Optics Characterization, H. Weber, H. Laabs, Eds., Technische Universität Berlin, Germany (2000) pp. 79 – 87.

7) S.V. Kukhlevsky, F. Flora, A. Marinai, G. Nytray, Zs Kozma, A. Ritucci, L. Palladino, A. Reale, G. Tomassetti: "Wave-optics treatment of X-rays passing through straight and tapered capillaries", Selected Research Papers on  Kumakhov Optics and Applications of 1998-2000, Ed. M.A. Kumakhov, SPIE-Russia-Chapter, Vol. 4155, pp. 61-71, 2000.

8) P. Di Lazzaro, S. Bollanti, F. Bonfigli, F. Flora, G. Giordano, T. Letardi, D. Murra, C.E. Zheng, A. Baldesi: “Amorphous silicon crystallisation by a long-pulse excimer laser", XIII Int. Symp. on Gas Flow and Chemical Lasers and High Power Laser Conf., A. Lapucci, M. Ciofini Eds., SPIE vol. 4184 (2001) pp.525 – 529.

9) P. Di Lazzaro, S. Bollanti, F. Flora, G. Giordano, T. Letardi, D. Murra, C.E. Zheng, A. Baldesi: “Laser eccimero industriale “Hercules L” e omogeneizzatore trasfocale di fascio” in 40 ANNI DI LASER, Collana Quaderni di Ottica e Fotonica vol. 7, a cura di C. Righini e M.A. Forastiere (CTE, 2001) pp. 113 – 117.

10)  F. Flora, S. Bollanti, A. Lai, P. Di Lazzaro, T: Letardi, A. Grilli, L. Palladino, G. Tomassetti, A. Reale, L. Reale, A. Scafati L. Bacchetta, M. Sanchez del Rio, T. Pikuz, A. Ya. Faenov: “A novel portable, high-luminosity monochromatically tunable X-ray microscope” in Applications of X-rays generated from lasers, G.Kyrala, J.C.Gauthier Eds., Proc. SPIE vol. 4504 (2001) pp. 240 – 252.
 

PATENTS

1) D. Murra, S. Bollanti, P. Di Lazzaro: “Sistema ottico per la omogeneizzazione spaziale di fasci di luce, con uscita a sezione variabile” (IT RM000229, filed on 28th April, 2000);
“Optical system for the homogenization of light beams, with variable cross-section output” (U.S. Patent and Trademark Office, n° 09/727268, filed on 30th November 2000; and European Patent Office, n° 00830807.4-2210, filed on 6th December, 2000)

2) F. Flora, L. Mezi, C. Zheng: "Processo di abbattimento del flusso di ioni e di piccoli detriti in sorgenti di raggi-X molli da plasma tramite l'uso di kripton", (IT RM 2000 A000636) filed on Dec. 1st, 2000.
“Abate process of ions and small debris flux in soft X-rays plasma laser sources by using krypton gas” (European Patent Office, No. 01830644.9, filed on Oct. 11th, 2001)

AWARDS

1) Award for the 2nd best communication at the LXXXVI Annual Congress of the Italian Physics Society (SIF), Palermo 6-11 October, 2000, Session Elettronica e Fisica del Plasma.  Communication title: "Sorgenti di radiazione EUV (hn = 100 eV) da plasma per microlitografia in proiezione”.

1) Award for the 2nd best communication at the LXXXVII Annual Congress of the Italian Physics Society (SIF), Milano 24-29 September, 2001, Session Elettronica e Fisica Applicata. Communication title: “Omogeneizzatore trasfocale di luce laser”