R. Teghil

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.

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.

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.

Spatial distribution of laser-ablated material by probing a plasma plume in three dimensions

Abstract A Pb0.2Bi1.8Sr2Ca1Cu2O{ce:italic}x{/ce:italic} target has been irradiated with 30 ns FWHM KrF excimer laser pulses having a wavelength of 248 nm and an energy density of ∼ 8 J/cm2. An intensified charge coupled device camera was used to measure the overall luminescence of the resulting plume in three dimensions as it moved from the target to the substrate. For small enough laser spots the plumes were found to have an ellipsoidal shape with {ce:italic}two{/ce:italic} distinct axes. On the other hand, for a large rectangular laser spot ({ce:inline-formula}3.0 × 1.2mm2{/ce:inline-formula} or {ce:inline-formula}2.4 × 1.0mm2{/ce:inline-formula}) the plumes were found to have an ellipsoidal shape with {ce:italic}three{/ce:italic} distinct axes. For example, at a time delay of 1000 ns the extensions were {ce:inline-formula}z = 34mm{/ce:inline-formula} (normal), {ce:inline-formula}y/2= 12mm{/ce:inline-formula}, and {ce:inline-formula}x/2= 8mm{/ce:inline-formula}, the lateral dimensions ({ce:inline-formula}x{/ce:inline-formula} and {ce:inline-formula}y{/ce:inline-formula} axes) being rotated at 90° with respect to the laser spot. The {ce:inline-formula}z{/ce:inline-formula} extension is sufficiently greater than those for {ce:inline-formula}x/2{/ce:inline-formula} and {ce:inline-formula}y/2{/ce:inline-formula}, and the {ce:inline-formula}z{/ce:inline-formula} expansion-front velocity is sufficiently high, that both {ce:italic}normal{/ce:italic} vaporization and {ce:italic}normal{/ce:italic} boiling can be excluded as the mechanisms of the laser sputtering. Subsurface explosion can be eliminated on the grounds that the analysis demonstrating its existence was wrong. It follows that either an electronic process or else phase explosion (also termed {ce:italic}explosive{/ce:italic} boiling) or else another still-to-be-defined but violent process may be involved. The results were finally compared with numerical solutions of the two-dimensional flow equations and a rotation effect was found essentially as observed. For example, it was largely absent at 200–700 ns, fully developed at 600–2000 ns, and, interestingly, starting to disappear at 3000–9000 ns.

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.

Pulsed laser ablation and deposition of semiconducting thin films : characterization of transient species

Abstract A study of laser-induced production and mass spectrometric analysis of ionized clusters from powder mixtures of the Group VI elements S, Se and Te and Cr, Fe, Ni, Cu, Ag, Zn, In and Cd is discussed. The binary systems Li2S, FeS, Ni2S, Ag2S, Ag2Te, ZnSe, CdS, CdSe and CdTe have also been investigated. The results show the formation of sequences of ionized products from laser ablation. Their relative stabilities are correlated to structure and reaction kinetics parameters.

Polycrystalline aluminum nitride films prepared by laser assisted Al and NH3 reaction

Abstract Aluminum nitride thin films have been fabricated by reaction of laser evaporated Al in a NH 3 atmosphere. The results indicate that AlN may deposit on a suitable substrate in a hexagonal crystal structure. A fairly dense homogeneous texture of the film surface morphology is seen by scanning electron microscopy (SEM). The main process parameters to produce layers of this material have been investigated.

Pulsed laser ablation: reactivity of photoablated neutral particles from FeCr alloy

Abstract In this paper experimental measurements taken in our laboratory on pulsed laser ablation of a FeCr alloy by Nd:YAG and KrF lasers are reported. REMPI ionization of the neutral Fe and Cr atoms formed indicates that the atoms in the excited states are not completely quenched when they are carried by the supersonic jet. The formation and stability of clusters of photoablated mono and diatomic metals with NH 3 molecules has also been investigated and the results show that they can generate electrostatic bonded clusters.