V. Marotta

Pulsed laser ablation and deposition of bioactive glass as coating material for biomedical applications

Abstract A study of the laser ablation and deposition, on Ti–Al substrates, of a biologically active glass (Bioglass®) suitable for bone implants is reported. The analysis of the gaseous phase by emission spectroscopy and the characterisation of the films from a compositional and morphological point of view have been carried out. The mean chemical composition of the deposits obtained from Bioglass ablation is very close to the target composition and the morphology indicates that different mechanisms of material ejection are present.

Characterization of the plasma plume and of thin film epitaxially produced during laser ablation of SnSe

Abstract Laser-induced ablation was applied to thin film deposition from a tin selenide target. Diagnostic methods are applied to the characterization of the laser ablated plume. Emission from atomic and ionic excited states of tin and selenium dominates the total emission of the plasma plume with excitation temperatures up to 12 000 K. A high-speed ICCD camera has also been used to study three-dimensional plume propagation. Positive and negative cluster ions of bare tin, selenium and of the combined elements have been detected by laser mass-spectrometry of the plume. The growth of SnSe has been analysed by electrical and optical techniques. The effect of laser fluence on the plume and on the properties of the deposits has also been studied. The epitaxial growth of SnSe on several substrates is reported.

Laser ablation and deposition of Bioglass 45S5 thin films

Abstract A study of the laser ablation and deposition, on Ti6Al4V substrates, of a biological active glass (Bioglass ® 45S5) is reported. The gaseous phase composition has been determined by laser ablation inductively coupled plasma mass spectrometry, optical imaging and emission spectroscopy. The deposited films were studied by scanning electron microscopy coupled with energy and wavelength dispersive X-ray analysis and X-ray diffraction. The adhesion of films to the substrates has been studied by scratch tests. Moreover, after exposing the coatings to a simulating body fluid solution, their bioactivity has been monitored by X-ray diffraction analysis of the hydroxylapatite growth. This procedure has been followed for different time scales up to a maximum of 24 days. The deposition mechanism seems to be related mainly to the mechanical transport of the target material in form of droplets, while the gaseous phase, having a very different composition, plays a marginal role. The overall film retains the target stoichiometry and bioactivity in a large range of experimental conditions.

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.

Study of the gaseous phase from pulsed laser ablation of titanium carbide

The gaseous phase of laser ablated TiC target has been analyzed by time of flight mass spectrometry and optical emission spectroscopy. Various molecular clusters TinCm, with n ranging from 1 to 4 and m from 1 to 5, are observed and the excited atoms emission spectrum is determined, together with the electronic temperature of the plume. The angular distribution of the material ejected from the target is also discussed.

Titanium nitride thin films deposited by reactive pulsed-laser ablation in RF plasma

Abstract Titanium nitride thin films were deposited on Si (100) substrates by pulsed laser ablation of a titanium target in a N 2 atmosphere (gas pressure approx. 10 Pa) using a doubled frequency Nd:YAG laser (532 nm) also assisted by a 13.56-MHz radio frequency (RF) plasma. Deposition was carried out at various substrate temperatures ranging from 373 up to 873 K and films were analyzed by X-ray diffractometry, scanning electron microscopy and optical emission spectroscopy. A comparison between the ‘normal’ pulsed laser deposition (PLD) and the RF plasma-assisted PLD showed the influence of the plasma on the structural characteristics of the thin films.

NbN superconducting thin films grown by pulsed laser ablation

Abstract NbN superconducting thin films have been grown by using pulsed laser ablation in a N 2 pure atmosphere. The X-ray spectra indicate that highly oriented superconducting NbN films having a FWHM of the 002 reflection narrower than 0.5°, has been obtained. Critical zero resistance temperature T c higher than 16.3 K and resistivity ratio ≈ 1.3 were measured as well as critical field of 12 T at LHe temperature on the high quality films. Transport critical current density J c , measured on a patterned film with a 50 μV cm criteria, gave an extrapolated value of J c0 higher than 1 × 10 7 A/cm 2 computed by using a Kim Andersen model. Preliminary photoemission spectroscopy measurements in the presence of N 2 background gas indicate some reactivity in the plume region.

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.

Sensors based on pulsed laser deposition of multilayers of metal oxides

Abstract Pulsed laser ablation has been utilized in our laboratory to deposit thin films of semiconducting oxides such as indium oxide and tin oxide. Deposition of these thin films has been carried out by a frequency doubled Nd-YAG laser (λ=532 nm) on silicon (100) substrates. A comparison has been performed, among indium oxide, tin oxide, and multilayers of indium and tin oxides, to evaluate their use as NO gas sensors. The influence of physical parameters, such as substrate temperature and laser fluence, on the velocity response of the films and on their resistance variation, has been investigated. The deposited films have been characterized by X-ray diffraction (XRD) and electric resistance measurements.

STUDIES ON NITRIDATION OF LASER EVAPORATED III-IV GROUP ELEMENTS WITH GASEOUS AMMONIA AND THIN FILM DEPOSITION

Abstract Groups III and IV nitrides have been viewed as promising materials in many technological applications, mostly in electronic devices and in ceramic materials. Many techniques such as CVD and MBE have been used to grow nitride thin films. A method to prepare nitrides by adding gaseous ammonia to laser evaporated elements has been developed in our laboratory. B, In, Si and Ge nitrides have been prepared by this method. The intermediate steps in nitride production have been examined by optical emission measurements and by mass spectrometry of the gas phase. The final products of the reaction have been characterized on various substrate surfaces by conventional techniques such as SEM, XRD and IR.