Papers by alessio perrone
Superficies y vacío, 1999
We have ablated, for the first time, graphite in a nitrogen atmosphere at different pressures by ... more We have ablated, for the first time, graphite in a nitrogen atmosphere at different pressures by using a sub-picosecond excimer Ž . laser KrF, s 248 nm, s 0.5 ps . In this paper, we have discussed the deposited film properties using several diagnostic L Ž techniques scanning electron microscopy, profilometry, X-ray photoelectron spectroscopy, Fourier transform, infrared and . Raman spectroscopies in terms of the different physical mechanisms involved in the reactive laser ablation process when the graphite target is ablated in a nitrogen atmosphere by lasers with different pulse duration. The deposition rate, the nitrogen concentration and the amount of the carbon bonded to nitrogen atoms were extremely reduced with respect to what was observed in the films deposited by nanosecond lasers. Moreover, the particulate and droplet density, one of the worst drawbacks of laser deposition technique, was not decreased.
Studio di fotoemissione da catodi di ittrio
Pulsed laser deposition in a chemically reactive environment: application to the synthesis and deposition of high quality thin films
From more than a decade now, the lasers have been applied to the synthesis and/ or the deposition... more From more than a decade now, the lasers have been applied to the synthesis and/ or the deposition of performnat thin films. The thin films are usually grown by laser chemical vapour deposition (LCVD). This method, however, suffers from the necessity of high-temperature substrate heating and usually resorts to dangerous gaseous precursors.
Applied Physics A, 2016
In this work yttrium and lead thin films have been deposited by pulsed laser deposition technique... more In this work yttrium and lead thin films have been deposited by pulsed laser deposition technique and characterized by ex-situ different diagnostic methods. All the films were adherent to the substrates and revealed a polycrystalline structure. Y films were uniform with a very low roughness and droplet density while Pb thin films were characterized by a grain morphology with a relatively high roughness and droplet density. Such metallic materials are studied because they are proposed as a good alternative to copper and niobium photocathodes which are generally used in radiofrequency and superconducting radiofrequency guns, respectively. The photoemission performances of the photocathodes based on Y and Pb thin films have been also studied and discussed.
Le Journal de Physique Colloques, 1979
Thin Solid Films, 2016
In this work, yttrium (Y) thin films have been deposited on Si (100) substrates by the pulsed las... more In this work, yttrium (Y) thin films have been deposited on Si (100) substrates by the pulsed laser deposition technique. Ex-situ morphological, structural and optical characterisations of such films have been performed by scanning electron microscopy, X-ray diffractometry, atomic force microscopy and ellipsometry. Polycrystalline films with a thickness of 1.2 μm, homogenous with a root mean square roughness of about 2 nm, were obtained by optimised laser irradiation conditions. Despite the relatively high thickness, the films resulted very adherent to the substrates. The high quality of such thin films is important to the synthesis of metallic photocathodes based on Y thin film, which could be used as electron sources of high photoemission performance in radiofrequency guns.
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2016
In this work, the authors compare the morphological, structural, nanomechanical, and microtribolo... more In this work, the authors compare the morphological, structural, nanomechanical, and microtribological properties of Pb films deposited by thermal evaporation (TE) and pulsed laser deposition (PLD) techniques onto Si (111) substrates. Films were investigated by scanning electron microscopy, surface probe microscopy, and x-ray diffraction in θ-2θ geometry to determine their morphology, root-mean-square (RMS) roughness, and microstructure, respectively. TE films showed a percolated morphology with densely packed fibrous grains while PLD films had a granular morphology with a columnar and tightly packed structure in accordance with the zone growth model of Thornton. Moreover, PLD films presented a more polycrystalline structure with respect to TE films, with RMS roughness of 14 and 10 nm, respectively. Hardness and elastic modulus vary from 2.1 to 0.8 GPa and from 14 to 10 GPa for PLD and TE films, respectively. A reciprocal friction test has shown that PLD films have lower friction co...
Physical Review E, 2015
We demonstrate that chemical reactions leading to the formation of AlO radicals in plasmas produc... more We demonstrate that chemical reactions leading to the formation of AlO radicals in plasmas produced by ablation of aluminum or Ti-sapphire with ultraviolet nanosecond laser pulses can be predicted by the model of local thermodynamic equilibrium. Therefore, emission spectra recorded with an echelle spectrometer and a gated detector were compared to the spectral radiance computed for uniform and nonuniform equilibrium plasmas. The calculations are based on analytical solutions of the radiation transfer equation. The simulations show that the plasmas produced in argon background gas are almost uniform, whereas temperature and density gradients are evidenced in air. Furthermore, chemical reactions exclusively occur in the cold plume periphery for ablation in air. The formation of AlO is negligible in argon as the plasma temperature is too large in the time interval of interest up to several microseconds. Finally, the validity of local thermodynamic equilibrium is shown to depend on time, space, and on the elemental composition. The presented conclusions are of interest for material analysis via laser-induced breakdown spectroscopy and for laser materials processing.
Carbon nitride coherently grown on Si (111) substrates by pulsed laser irradiation
ALT '99 International Conference on Advanced Laser Technologies, 2000
Carbon nitride films were deposited on Si substrates at room temperature by XeCl laser ablation o... more Carbon nitride films were deposited on Si substrates at room temperature by XeCl laser ablation of graphite targets in low pressure N2 atmosphere at the fluence of 12 J/cm2. The films have been submitted to x-ray diffraction and transmission electron microscopy investigations in order to study the structure of the films. Results showed that the samples are constituted of a
Parametric studies of carbon nitride thin films deposited by reactive pulsed laser ablation
ALT '99 International Conference on Advanced Laser Technologies, 2000
We report on parametric studies of CNx films deposited by excimer laser ablation of graphite targ... more We report on parametric studies of CNx films deposited by excimer laser ablation of graphite targets in molecular nitrogen atmosphere as a function of gas pressure and laser fluence values. Substrates were Si single crystals at room temperature. Deposition rates decrease with increasing nitrogen pressure. The N/C atomic ratio generally increases with increasing nitrogen pressure and laser fluence, N atoms
Radiation Physics and Chemistry (1977), 1983
The role of the adsorbed gases on the photoelectron performance of Mg-based photocathodes
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2008
The influence of the adsorbed gases on the photoelectron performance of Mg thin film-based photoc... more The influence of the adsorbed gases on the photoelectron performance of Mg thin film-based photocathodes was investigated. Mg thin films were deposited on Silicon and Copper substrates by pulsed laser ablation technique. The samples deposited on Silicon substrate were used to deduce the morphology, the structure and the thickness by using different diagnostic techniques. On the contrary, the samples deposited
Proceedings of the 2005 Particle Accelerator Conference
Advanced high brilliance electron injectors require photocathodes having low thermal emittance, h... more Advanced high brilliance electron injectors require photocathodes having low thermal emittance, high quantum efficiency (QE) and prompt response. They should be easy to handle and capable of working in the very high electric fields of a RF gun. Magnesium films deposited by laser ablation and sputtering techniques are discussed and QE measurements are presented.
2007 IEEE Particle Accelerator Conference (PAC), 2007
Metallic film photo-cathodes are rugged, have a fast response and good emission uniformity. Mg ha... more Metallic film photo-cathodes are rugged, have a fast response and good emission uniformity. Mg has also a relevant Quantum Efficiency (QE) in the near UV. A cathode suitable for a 1.5 cells S-band RF gun has been produced by depositing an Mg film on Cu by Pulsed Laser Deposition (PLD) technique. After different optimizations, stable good results have been reached in the low field measurement scenario. A sample was deposited on a gun flange and tested in the 1.6 cell injector at UCLA Pegasus facility to prove cathode resistance in a high field environment. The results are described.
Morphological Changes and Plume Deflection Effect during Pulsed Laser Ablation Deposition of Al
Materials Science Forum, 2007
The morphological changes and corresponding plume deflection effect during long laser (XeCl excim... more The morphological changes and corresponding plume deflection effect during long laser (XeCl excimer laser, λ=308 nm, τ=30 ns) irradiation of Al target have been investigated,and results showed that, a the number of laser pulses per site increases, the target morphology changes and produces a visible deviation of the plasma plume up to 5º. Scanning electron spectroscopy analys of the target surface related the plume deflection angle to the target morphology and the number of laser pulses per site. Typically well-defined columnar structures oriented along the laser beam direction were observed on the target surface. The plume created during the laser ablation was clearly visible to the naked eye and was recorded by a digital camera. Detailed studies were also performed on the ablation rate at different laser fluences (4.6 J/cm2-12.5 J/cm2). The morphologies and the thickness of the Al thin films deposited on Si substrates during the present laser ablation experiments were also studied...
Thin Solid Films, 2015
Pb thin films were prepared by the ns pulsed laser deposition technique on Si (100) and polycryst... more Pb thin films were prepared by the ns pulsed laser deposition technique on Si (100) and polycrystalline Nb substrates for photocathode application. As the photoemission performances of a cathode are strongly affected by its surface characteristics, the Pb films were grown at different substrate temperatures with the aim of modifying the morphology and structure of thin films. Atomic force microscopy and scanning electron microscopy analyses showed a strong morphological change in the deposited films with the substrate temperature, and the formation of spherical grains at higher temperatures with the nucleation of large voids on the film surface. X-ray diffraction measurements showed that a preferred orientation of Pb (111) normal to the substrate was achieved at 30 °C while the Pb (200) plane became strongly pronounced with the increase in the substrate temperature. Finally, a Pb thin film deposited on Nb substrate at 30 °C and tested as the photocathode showed interesting results for the application of such a device in superconducting radio-frequency guns.
<title>Laser reactive ablation deposition of carbon nitride thin films</title>
High-Power Lasers: Applications and Emerging Applications, 1996
ABSTRACT
Reactive laser ablation deposition of C-N films
SPIE Proceedings, 1996
Reactive laser ablation deposition of CN films. [Proceedings of SPIE 2777, 128 (1996)]. Gilberto ... more Reactive laser ablation deposition of CN films. [Proceedings of SPIE 2777, 128 (1996)]. Gilberto Leggieri, Armando Luches, Alessio Perrone, S. Acquaviva, Rodica Alexandrescu, Ion N. Mihailescu, Joseph Zemek, Paolo Mengucci. Abstract. ...
<title>Parametric study of C-N films deposited by reactive laser ablation</title>
Nonresonant Laser-Matter Interaction (NLMI-9), 1997
ABSTRACT
Thin Solid Films, 1995
Titanium carbide films were deposited on silicon wafers by XeCl(308 nm) excimer laser ablation of... more Titanium carbide films were deposited on silicon wafers by XeCl(308 nm) excimer laser ablation of titanium in low pressure ( 10 3 mbar) methane atmosphere. Series of 10 000 pulses at the repetition rate of 8 Hz were directed to the target surface. The fluence was set at about 5 J cm-'. Pulse duration was about 30 ns. The deposited films were characterized by different techniques (X-ray diffraction, scanning electron microscopy and Rutherford backscattering spectrometry).
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Papers by alessio perrone