Diamond-like carbon (DLC) films have a unique combination of physical and chemical properties such as high hardness, optical transparency, low coefficient of friction and chemical inertness. A pulsed laser (248 nm) has been used to ablate a pyrolytic graphite target to deposit DLC films on Si (100) and 7059 Corning glass substrates. The deposition was carried out in high vacuum (≤ 10−6 Torr) at different temperatures ranging from room temperature to 400°C. The films were characterized by x-ray diffraction, scanning electron microscope, and Raman spectroscopie techniques. The mechanical properties (hardness and Young's modulus) of these films were characterized by nanoindentation. We have found that the films deposited at room temperature and 100°C show the characteristic features of DLC films and have the better hardness and modulus properties compared to the films fabricated at higher temperatures, which transform into amorphous carbon. Correlations of pulsed laser deposition process parameters with the properties of deposited DLC films will be discussed in this paper.

We have deposited unhydrogenated diamond-like carbon (DLC) films with 100 femtosecond laser pulses, at intensities in the 3x1014 - 6.5x1015 W/cm2 range. Film surface topography, optical property, and bonding structure were examined, respectively, with atomic force microscopy (AFM), spectroscopie ellipsometry (SE) and Raman spectrometry. The femtosecond pulse generated plasma was studied through time-of-flight (TOF) experiment. The most probable kinetic energy of carbon ions was estimated to be in the 300 – 2000 eV range, increasing with laser intensity. In addition, a unique ‘suprathermal’ component with kinetic energy ranging from 4 to 40 keV was observed in the TOF spectrum. This high energy peak is believed to originate from fast ions in a solid density plasma created during the absorption of each femtosecond laser pulse.

The fabrication of sensors and actuators requires new materials with multicomponent stoichiometry as well as new three-dimensional microstructures. We present several potential applications of laser processing for the fabrication of sensors and actuators. The first example concerns gas sensors which require ionic conductor multicomponent ceramics whose stoichiometry is not maintained by conventional sputtering methods. We have successfully employed pulsed laser deposition (PLD) for producing high quality NASICON (Na SuperIonic CONductor) thin films. XPS measurements show that all elements are transferred from a target of Na1+xZr2SixP3-xO12, (where 0 < x < 3 ) to the substrate, and that the composition of the thin film is very close to that of the target. Electrical measurements show good ionic conductivity. Thus, these films are suitable for the fabrication of electrochemical gas sensors. Since such ceramic thin films are very sensitive to liquids, wet etching is prohibited, and patterning is done using laser ablation. For other applications, a laser micromachining technique has been developed to make tunnels and cavities in Si under SiO2 films, based on the laser-induced CI2 etching of Si and high chlorine Si/SiO2 etch rate ratios. Tunnels with length of up to 3 mm and cavities of 100×100 cm2 were successfully fabricated in SiO2/Si bilayer samples. These are usable in microfluidic or gas pressure measurement systems.

Laser-induced etching of polycrystalline Al2O3TiC material by a tightly-focused CW Ar ion laser has been investigated in a KOH solution with different concentrations. It is found that the KOH concentration can strongly affect the etching quality where low KOH concentration can result in rough and irregular patterns. The etching effect is also related to laser power and scanning speed. Laser-induced etching of polycrystalline AI2O3TiC in a KOH solution is found to be a photothermal reaction in which a threshold laser power exists. With an appropriate set of etching parameters, well defined grooves can be obtained with clean side walls and with an etching rate up to several hundred micrometers per second. It is also found that the grains in the polycrystalline Al2O3TiC material play an important role in the etching dynamics and etching quality. This etching process is believed to be applicable to the formation of a slider surface of magnetic heads in the future.

Excimer laser ablation is applied in the deflashing and demarking of IC packages. It is found that mold flash filled in the interface holes of IC leadframe can be removed completely by the laser deflashing in a short period of time. With appropriate selection of laser parameters, deflashing quality and efficiency can be greatly improved. The laser deflashing is more efficient for higher pin count packages. It is a superior alternative in future applications. In laser demarking, ink marks on package surfaces can also be removed completely in a short time. The surface after the processing has good conditions for remarking. The package remarking shows good permanency. The lifetime for good marking is much longer for IC packages after the laser demarking than those after hydrogen flame-off. Laser processing can be used to replace hydrogen flame-off in the ink printing of IC packages for high efficiency and safety.

Laser dry cleaning of ZrO2 particles from air bearing surface (ABS) of magnetic head sliders has been investigated. The experimental results show that the cleaning threshold of removing ZrO2 particles from ABS is about 100 mJ/cm2. For laser fluence larger than this threshold, cleaning efficiency increases with increasing laser fluence and pulse number, but does not depend on repetition rate up to 30 Hz. The mechanisms of this laser dry cleaning are laser-induced ABS vibration, particle thermal expansion and particle vibration, which produce forces strong enough to detach ZrO2 particles from ABS. With increasing laser fluence and pulse number, the average acceleration and vibration number of particles induced by laser increase respectively, so that it is easier to remove particles which corresponds to higher cleaning efficiency. For fixed laser fluence and pulse number, changing the repetition rate does not change the average acceleration or the vibration number of particles, therefore laser cleaning efficiency is almost the same for different repetition rates.

A surface-cleaning and preparation method that uses high-energy photons and a laminar flowing inert gas has been demonstrated as a feasible technology for broad-based industrial applications such as semiconductors, electronics, optics, coated optical and magnetic media, automotive, aerospace and art restoration. This technology is flexible in tool embodiment and is environmentally friendly because no water and chemicals are not used.

Directed light fabrication (DLP) is a rapid fabrication process that fuses gas delivered metal powders within a focal zone of a laser beam to produce fully dense, near-net shape, 3-dimensional metal components from a computer generated solid model. This study used iron-based alloys to evaluate the microstructural development in the DLF process. Continuous microstructural features are evident, implying a continuous liquid/solid interface during processing. In addition, solidification cooling rates have been determined based upon secondary dendrite arm spacings in Fe-25wt.%Ni and 316 stainless steel. Cooling rates vary from 101-105 K s-1, and the solidification behavior has been simulated using macroscopic heat transfer analyses.

We describe a novel laser chemical process having potential for optical data storage and processing applications. Reversible oxygen exchange involving WO3, using readily available laser sources offers improved durability and versatility over existing erasable optical data storage media. Being interconvertable using heat and blue-green laser sources, the well known yellow WO3 and blue W2O5 can function as erased and written states.

Ultraviolet light having sufficiently short wavelength can drive photochemical processes at polymer surfaces. We find that irradiation at 193 nm, but not at 248 nm, results in conversion of amide groups at the nylon surface to amines, still bound in the polymer chain. These amines show anti-microbial activity [1].

Complex oxide perovskites, namely strontium aluminum tantalum oxide (SAT) and strontium aluminum niobium oxide (SAN) were recently investigated to be potential substrate materials for HTSC films in microwave applications. Single crystals were prepared by laser heated pedestal growth technique (LHPG). We report Raman vibrational spectrum studies on them for the first time. Order-disorder effects of (Al, Ta) and (Al, Nb) sites were studied with particular interests by comparing Raman spectra of single-crystal samples with ceramic samples. Influences of B sites (Ta and Nb) on O-O modes are discussed in relation to their dielectric properties.

Reactive laser ablation of Si targets by ArF* excimer laser (wavelength 193 nm, pulse width 15 ns (FWHM)) was performed in He, Ar or O2 0.05-1 Torr atmospheres and led to Si-SiOx nanocluster thin film formation within laser-induced plasma plume. Optical spectroscopy and optical Time-of-Flight (TOF) measurements were carried out during ablation-deposition experiments. A number of large weak emission bands in blue and green-yellow spectral branches were observed both in inert gases and in oxygen ambient atmospheres and attributed to the emission from excited nanoparticles in the plasma plume. TOF measurements proved a different spatio-temporal evolution of this emission compare to the emission of monoatomic particles. The films exhibit photoluminescence bands in the UV region (around 290 nm and between 310-370 nm), in the blue (between 420 and 500 nm), and in the green-yellow (at 520-560 nm). The relative intensities of the luminescence bands depend on the average cluster size, which is determined by preparation conditions (nature and pressure of the ambient gas, laser fluence).

We report the preparation of the nanometer Si crystallites constrained between a-SiNx:H barrier layers by means of KrF excimer laser induced crystallization. X-ray diffraction (XRD) and Raman scattering spectra demonstrate that ultra thin a-Si:H well layers have been crystallized. The average grain size of Si crystallites is on the order of magnitude of a nanometer. Small-angle XRD spectrum indicates multilayer structures have not undergone laser damage. The results of TEM are presented to show smooth and abrupt interfaces of layered structures and nanometer Si crystallites arrayed one-by-one in the Si layer. The thermodynamics of KrF laser-induced crystallization of ultra-thin Si layer has been discussed.

Thin films composed of size selected silicon nanocrystallites have been fabricated and their photoluminescence behavior has been studied. The silicon nanocrystallites were produced using a pulsed laser ablation supersonic expansion source. This source typically generates silicon clusters of many different sizes, which leads to photoluminescence spectra with a large fiill width at half maximum. To best utilize our gas phase synthesis technique, we have performed size selection of the silicon clusters using a mechanical velocity selection apparatus. Films of these size selected nanocrystallites exhibited photoluminescence spectra which had a smaller full width at half maximum and which were peaked to the blue of the spectra of samples with a broader size distribution. These results suggest that the photoluminescence wavelength of these nanocrystallite thin films is determined by quantum confinement of the electrons and holes in the crystallites.

Very high-strength alloys of Al(O) have been formed using a pulsed laser deposition (PLD) system to deposit from alternating targets of Al and Al2O3. Ion beam analysis and transmission electron microscopy show that the deposited material is uniform in composition with up to 33 at.% O and has a highly refined microstructure consisting of a fine, uniform dispersion of ∼1 nm diameter γ-Al2O3 precipitates. Ultra-low-load indentation testing combined with finite-element modeling is used to determine the mechanical properties of the layers. Yield stresses as high as 5.1 GPa have been measured in these materials, greatly exceeding the strengths of aerospace Al alloys (∼0.5 GPa) and even high strength steels. The key to the properties of these materials is the dispersion of small, hard precipitates spaced only a few Burgers vectors apart; dislocations are apparently unable to cut through and must bow around them.

Samples of Fe78B13Si9 and Fe81B13.5Si3.5C2 metallic glasses were irradiated with a pulsed alexandrite laser (λ=750 nm, τ=60 μs) using different laser fluences. Kinetics of laser-induced phase transformations and fluence dependence of magnetic properties were studied by scanning electron microscopy (SEM) and Mössbauer spectroscopy. Low laser fluences were found to induce changes in magnetic texture and onset of crystallization. High laser fluences, however, correlated with additional oxidation effects and the formation of stoichiometric Fe3O4 particles in the irradiated alloy system. An activation energy of 11.9 eV was estimated for the laser-driven synthesis of magnetite nanoparticles. Pulsed alexandrite laser processing is an intriguing alternative technique for the controlled synthesis of iron oxide phases from ferromagnetic glass precursors.

By optimizing various experimental parameters, we were able to extend the width of the microstructually optimized regions in grain-boundary-location-controlled (GLC) Si films up to 10 μm. In situ transient reflectance (TR) measurements during the solidification process reveal that the underlying GLC transformation sequence is consistent with the artificially controlled super-lateral growth (ACSLG) scenario, from which the GLC process was developed and is being optimized. A definite change in the slope of the TR signal was found to appear at the transition between the vertical-and-lateral -growth and lateral-growth-only modes. Protrusions at the center of the GLC Si microstructure, which are observed in cross-sectional TEM micrographs and surface profile measurements, are formed as a result of the positive volume change associated with freezing of Si.

Laser ablation of semiconductors presents an increasing interest for both thin film growth and surface modification. We present herein a study of the damage produced in bulk silicon by nanoseconds UV laser pulses with energy above the melting threshold. This study is carried out with a Raman microprobe. Polarized microRaman was used to reveal the main changes in the melted and recrystallized volume. These changes were observed in the liquid/solid boundaries, where tensile stress due to the induced thermal wave is more important. The morphology of the melted region evidences matter accumulation at such a boundary.

Ferroelectric PbZr0.44Ti0.56O3 film with pure ferroelectric phase was fabricated by Ar3+ and KrF laser crystallization technique from as-deposited amorphous films, with the substrate at room temperature. Laser annealing technique was also used to improve the quality of BaTiO3 (BT) films.

PECVD amorphous silicon films deposited at different temperatures on low cost glass substrates have been treated by a Single Shot Excimer Laser Annealing (SSELA) at various energy densities. The influence of a thermal treatment at medium temperature (400°C) prior to the SSELA treatment was also investigated. Spectroscopie ellipsometry and Raman characterizations show that hydrogen contamination produces an important roughness increase with very little polycrystalline grains (650nm) after laser treatment. The thermal treatment prior laser annealing improves drastically the structural quality of the films. Structural results are correlated with the electrical performances of the TFT produced on these films.