C. Flamini

AIN thin film deposition by pulsed laser ablation of Al in NH3

Abstract Aluminium nitride films were synthesized by reaction of laser-evaporated Al in NH3 atmosphere. Optical multichannel emission spectroscopy (OMA) and intensified charge coupled device (ICCD) imaging have been applied to in situ identification of deposition precursors in the plasma plume moving from the target to the substrate. Mass spectrometry has also been used to detect ionic species ejected from an Al target in a mixture with NH3. Thin films prepared by this method were characterized by conventional techniques such as Auger, energy dispersive analysis of X-ray (EDAX), scanning electron microscopy (SEM), and X-ray diffraction. Highly oriented films of AIN (100) on Si (100) were identified.

Luminescence from pigments and resins for oil paintings induced by laser excitation

Abstract The present work reports results of an extensive study of laser induced luminescence by tripled Nd:YAG laser ( λ =355 nm) of a few most common painting materials, namely, natural and synthetic pigments and resins. The luminescence spectra have been analyzed by an Optical Multichannel Analyzer (OMA III). Luminescence time decay has been measured by a Streak camera or by the OMA III. Pigments and resins show characteristic emission spectra with bands peaking in the visible. The decay ranges from less than 1 ns up to 700 μ s for pigments and for resins. The mechanism of excitation and relaxation leading to luminescence is discussed for the various materials. Oil colour specimens have been irradiated by a UV KrF laser ( λ =248 nm). Luminescence photographs have been detected by an intensified charge coupled device (ICCD) camera at different time delays.

Reactive pulsed laser ablation and deposition of thin indium tin oxide films for solid state compact sensors

Thin indium tin oxide (ITO) films have been deposited on Si (100) substrates by laser ablating pure metals in oxygen atmosphere. The ablation has been carried out by a frequency doubled Nd:YAG laser and the oxygen pressure has been varied between 50 and 500 Pa. The substrate temperature has been varied from 25 to 700°C. The gaseous phase has been studied by mass spectrometry and fast ICCD imaging. The deposited films have been analysed by X-ray diffraction, scanning electron microscopy and electric resistance measurements.

Angular distribution and expansion of laser ablation plumes measured by fast intensified charge coupled device photographs

Abstract Laser ablation plumes produced from various targets including metals, semiconductors, and superconductors have been photographed in real time with a gated, intensified charge coupled device (CCD) camera system. The expansion rates of the three-dimensional images have been measured in a wide range of delay times after the laser pulse by varying the beam parameters such as spot size, spot shape, and fluence. The analysis of the observed plumes leads to the angular distribution of the ablated material which is strongly related to the process of film growth by pulsed laser deposition.

Ablation of transition metal oxides by different laser pulse duration and thin films deposition

Thin films of transition metal oxides are of interest in many applications such as anticorrosion coatings and optical and electrochromic devices. In this work, the effect of different wavelength and pulse duration on ablation of oxides target has been investigated. The plume has been characterized by mass spectrometry and optical spectroscopy. Ablation thresholds have been measured by detecting ion emission from the target and from the onset of the plume luminescence. Morphology and optical properties of thin films deposited in different conditions are presented.

Reaction of Al with ammonia by pulsed laser ablation: Optical analysis and mass spectrometry

Abstract In situ techniques have been employed to characterize laser plasma (plume) formation and reactions in the gas cloud formed from Al and NH 3 . Optical emission imaging and spectroscopy, and time of flight mass spectrometry have been used to monitor ablation plume components. AlN films have been synthesized by reaction of laser evaporated Al in a NH 3 atmosphere. Optical multichannel emission spectroscopy (OMA) and intensified charge coupled device (ICCD) imaging have been applied to identification of the deposition precursors occurring in the plasma.

Time-resolved studies of electron-phonon relaxation in metals using a free-electron laser

Here we report recent experiments on ion emission from metals (Ti, Nb, Mg) using a free-electron laser that delivers a train of subpicosecond micropulses in the mid-infrared (IR). The laser intensities for the surface damage and ion emission thresholds are used as markers for the onset of energy transfer to the lattice for ablation. Numerical calculations based on the Anisimov two-temperature model are used to evaluate the electron temperature Te and the lattice temperature Ti. The results are discussed in terms of the Hertz–Knudsen equation for vaporization and a model based on laser-induced multiple electronic transitions.

Zirconium oxide films deposited by reactive pulsed laser ablation

Abstract Laser ablation, by Kr–F and Nd–YAG lasers, of solid targets of ZrO2 has been studied in vacuum and in oxygen atmosphere. The plume expansion and composition have been characterized by mass spectrometric and optical techniques. Cluster ions ZrxOy and neutral species, formed in the plasma, have been identified by mass spectrometry. Plume velocity has been measured by a ICCD camera. Buffer gas effects and geometrical parameters have been optimized to improve the quality of the deposited thin films.

Laser-induced evaporation, reactivity and deposition of ZrO2, CeO2, V2O5 and mixed Ce-V oxides

Abstract It has been found that pulsed laser ablation has good potentiality for the deposition of ZrO2, CeO2, V2O5 and mixed Ce-V oxides which are very important materials for their application in optics and electrochromic devices. Laser induced compositional changes of thin films in the ablation and deposition processes of these materials have been explored. The effect of the oxygen gas pressure on the thin film composition has been examined. The congruency of the process has been treated on the basis of a thermal mechanism of evaporation–decomposition of the compounds. An attempt to model the processes by means of a thermodynamic approach is reported.

Preparation of the group III nitride thin films AlN, GaN, InN by direct and reactive pulsed laser ablation

The methods of preparation of the group III nitrides AlN, GaN, and InN by laser ablation (i.e. laser sputtering), is here reviewed including studies on their properties. The technique, concerns direct ablation of nitride solid targets by laser to produce a plume which is collected on a substrate. Alternatively nitride deposition is obtained as a result of laser ablation of the metal and subsequent reaction in an NH3 atmo- sphere. Optical multichannel emission spectroscopic analysis, and time of flight (TOF) mass spectrometry have been applied for in situ identification of deposition precursors in the plume moving from the target. Epitaxial AlN, GaN, and InN thin films on various substrates have been grown. X-ray diffraction, scanning electron microscopy, have been used to characterise thin films deposited by these methods.