Silicon-carbide (SiC) has excellent refractivity in the range of soft X-ray and is well-used as a diffraction grating for Synchrotron-radiation (SR) light. This material has a high melting point, hardness and chemical stability. Therefore, etching of the material by chemical or physical methods is very difficult. We reported a photo-chemical etching method in which a SiC surface is placed in NF3 gas atmosphere and irradiated by the Xe2* excimer lamp light parallelly and the grating patterned KrF laser light of 248nm perpendicularly on the sample surface. The Xe2* excimer lamp light are employed for NF3 gas decomposition, and KrF laser light used for excitation on the sample surface. This photochemical etching reaction are detected by XPS, QMS and FTIR measurements. This method achieved 0.18 Å/shot in etching efficiency, and became maximum approximately 7 times as high as ArF laser light for photodecomposition.

Polyimide sheet surface was photochemically modified to be hydrophilic property with Xe2* excimer lamp ( λ =172nm) irradiation and pure water solution. The solution was sandwiched between the surface and fused silica glass. With the excimer lamp irradiation, the solution and the surface were excited; the surface was dehydrogenated by the hydrogen atoms which were photodissociated from pure water and replaced the photodissociated OH radicals. The hydrophilic property of the modified surface was evaluated by measuring the contact angle with water. The replacement of the OH radicals were confirmed by FTIR. The modified surface was bonded to stainless steel with an epoxy resin for evaluation of the adhesive strength by the shearing tensile test. As a result, the adhesion was increased to 1.4 times that of the non-irradiated sample.

The surface of partially stabilized zirconia ceramics was irradiated by a Nd:YAG laser in various atmospheres. Zirconia strongly absorbed YAG's laser beam and changed its chemistry and microstructure. The change of color of zirconia into gold was due to the formation of zirconium nitride (ZrN) observed on the irradiated surface in air, nitrogen or ammonia, which was confirmed by X-ray diffraction and secondary ion mass spectroscopy. The observed ZrN phase was 10-20 um in thickness at the irradiated area by the direct beam. The adhesion between formed ZrN and YSZ substrate was very weak.

We have developed a novel laser assisted method to fabricate unique modified surface composites which have industrial applications ranging from improved adhesion of coatings to improved bio-compatibility. The surface consists of two materials with linear variation in composition, thus leading to linear variation in thermal expansion coefficients. The fabrication process is based on the use of a pulsed excimer laser with an energy fluence near the ablation threshold. Using this method we have been able to create adherent diamond coatings on cutting tool materials, high surface area bio-compatible hydroxyapatite ceramics and Mo/W surface composites. This process has also increased the adhesion of coatings in large thermal mismatched systems like diamond on steel substrates.

This paper gives an overview on different types of instabilities and structure formation in various fields of laser processing. Among the examples discussed in detail are non-coherent structures observed in laser-induced chemical vapor deposition (LCVD), in laser-induced surface modifications, and in laser ablation of polymers.

The growth of high quality amorphous hydrogenated semiconductor films was explored with different in situ spectroscopic methods. Nucleation of ArF laser-induced CVD of a-Ge:H on different substrates was investigated by real time ellipsometry, whereas the F2 laser (157nm) deposition of a-Si:H was monitored by FTIR transmission spectroscopy. The ellipsometric studies reveal a significant influence of the substrate surface on the nucleation stage, which in fact determines the electronic and mechanical properties of the bulk material. Coalescence of initial clusters occurs at a thickness of 16 Å for atomically smooth hydrogen-terminated c-Si substrates, whereas on native oxide covered c-Si substrates the bulk volume void fractions are not reached until 35 Å film thickness. For the first time we present a series of IR transmission spectra with monolayer resolution of the initial growth of a-Si:H. Hereby the film thickness was measured simultaneously using a quartz crystal microbalance with corresponding sensitivity. The results give evidence for cluster formation with a coalescence radius of about 20 Å. Difference spectra calculated for layers at different depths with definite thickness reveal that the hydrogen-rich interface layer stays at the substrate surface and does not move with the surface of the growing film. The decrease of the Urbach energy switching from native oxide to H-terminated substrates suggests a strong influence of the interface morphology on the bulk material quality.

An argon-ion laser based direct-writing technique was used to deposit micron-size silicon lines from the decomposition of silane (SiH4) and trisilane (Si3H8) gases. The substrates used were 0.1 μrn polysilicon/1 μ.m silicon dioxide/<100> monosilicon multilayered structures. The vertical silicon deposition rate was investigated as a function of the laser-induced surface temperature and gas pressure. For temperatures ranging between 1000 and 1410 °C, the pressure was varied in the range 5-250 mbar and 0.1-30 mbar for SiH4 and Si3H8, respectively. For both gases, three growth regimes could be distinguished according to precursor pressure. The deposition rates achieved using trisilane are far higher than those obtained with silane in spite of the use of a reduced gas pressure range. For a laser-induced surface temperature of 1300 °C and a precursor pressure of 10 mbar, the deposition rates achieved using SiH4 and Si3H8 are, respectively, 0.42 and 20 μ.m/s, representing an enhancement factor of 50 with the later.

A systematic study of the composition of Ni-Fe steel microstructures grown from iron pentacarbonyl and nickel tetracarbonyl by direct laser-induced pyrolysis is presented. The partial pressures of both precursors were varied from 2 to 40 mbar, resulting in needles of iron, nickel, and iron-nickel alloys. An Ar+ laser was employed at incident powers of 100 to 600 mW. Auger Spectroscopy and a microprobe were used to determine the composition of the needles vs. partial pressure and laser power. Composition was also measured along the length of the rods to determine temperature changes during needle growth. This latter effect is useful in modelling the heat flow mechanisms during 3-dimensional laser CVD, as the threshold decomposition temperatures of Fe(CO)5 and Ni(CO)4 differ and the composition of the rods affects their thermal conductivity. In some iron samples, periodic banded structures were observed along the length of the rods, indicative of periodic melting. Axial deposition rates were also measured relative to laser power density, and rates up to 40 μm/s were achieved. Photolysis in the gas phase was observed for the iron-nickel carbonyl mixture, and was largely eliminated with a high-pass UV filter at 420nm. Additional disassociation of the carbonyl groups produced carbon soot near the reaction zone, but only for high nickel carbonyl concentrations. Convective cooling of the needles during growth was determined to be the primary heat transfer mechanism.

High quality diamond spots were deposited on silicon substrates by a hot filament process combined with laser heating. A mixture of CH4(1.8 vol%) and H2was passed over a tantalum filament having a temperature of about 2200 °C. The substrate temperature was varied by small adjustments of the filament power. A focused laser beam was used to locally raise the temperature on the substrate surface. By a proper choice of filament temperature, background substrate temperature and laser induced temperature, isolated islands of polycrystalline diamond could be deposited on the silicon substrate. The deposited diamond spots were characterized by micro-Raman spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and scanning force microscopy.

Hydrogen-containing amorphous carbon films were produced from CH,I, by photolytical laser assisted chemical vapour deposition at room temperture. An Ar+ laser operated in the ultraviolet spectral region (351 and 364 nm) was used as the excitation source. The beam was focused in parallel to the Si(lOO) substrate. The deposition process was studied for different partial pressures of CH,I2 and for different heights of the laser beam above the substate surface. The mass thickness of the film was determined by energy dispersive X-ray spectrometry. The hydrogen content of the carbon films was determined by nuclear reaction analysis and the iodine content in the films was obtained by Auger electron spectroscopy and energy dispersive X-ray spectrometry. Carbon hybridization was investigated by Raman and infrared spectroscopy while morphology was examined by atomic force microscopy.

The nucleation of tungsten on bare Si and SiO2/Si surfaces by Ar ion laser induced CVD has been studied with high speed real-time specular reflection and scattering. Our experimental results show that the induction time of tungsten nucleation decreases with laser power and is longer on thicker SiO2 surfaces than on thin native SiO2 surfaces at the same laser power. The activation energy of tungsten nucleation on native SiO2/Si obtained from an Arrhenius plot of induction time is about 33 kJ/mol at temperatures less than 1000 K and 16 kJ/mol at temperatures higher than 1000 K. The results on bare Si with and without H2 reveal that the initial reaction mechanism appears to be the same in both cases. An Arrhenius plot of induction time shows two different apparent activation energies at different temperature ranges, which suggest that W nucleation is controlled by H atom desorption from the Si surface at temperatures less than 714 K and is dominated by Si atom reduction of WF6 molecules at surface temperatures greater than 800 K.

Illumination of titanium thin films with an argon-ion laser has been used to fabricate nanometer scale features by localized oxidation. The laser induces a temperature gradient in the metal film, within which oxidation may occur. Due to the non-linearity of the reaction with temperature, the reaction zone can be laterally confined to regions narrower than the diffraction limit of optical resolution. Scanning probe microscopy indicates widths ranging from 105 to 600 nm and heights of 0.8 to 30 nm. The possibility of forming novel structures is demonstrated.

Direct writing of GaAs optical waveguides has been achieved by laser assisted chemical vapor deposition (LCVD). The multimode waveguides have gaussian-like cross sections, smooth surfaces, and exhibit losses as low as 5.4 dB/cm. The LCVD technique offers the capability of maskless in situ selective epitaxial growth of diverse multilayer structures, and is therefore a novel alternative for the monolithic integration of optoelectronic integrated circuits.

Aluminum conductor lines were deposited on Si substrates from liquid phase triisobutylaluminum (TIBA) using a scanned argon ion laser. The vertical growth rate of Al lines initially increased, then decreased with increasing dwell time. The maximum vertical growth rate occurred at a particular dwell time depending upon the laser power. Lower vertical growth rates at longer dwell times are propably caused by the depletion of the reactant at the reaction site. A volcano deposit shape was observed, which became more pronounced as dwell time increased. The conductivity of the as-deposited Al lines decreased with increasing dwell time for our experimental conditions. To study the deposition kinetics and calculate the activation energy, the temperature rise on the Si surface was calculated by solving the nonlinear heat equation using finite difference method.

The laser chemical vapour deposition (LCVD) of the organometallic precursor Cu(hfac)TMVS (hexafluoroacetylacetonate)(trimethylvinylsilane) is used to grow copper films on a Teflon AF1600 substrate. Exposure to excimer laser radiation at 248 nm results in a terraced copper growth. A simple model, based on interference effects in the Teflon and copper layers, is presented to account for this structure.

Excimer laser photolysis has been used for the growth of smooth and well-adhering thin films of aluminum nitride (AlN) on Si, fused quartz, and KBr substrates at temperatures as low as 350 K. The photolysis was carried out at 193 nm, with the laser beam propagating parallel to the substrate. Trimethylamine alane and ammonia were used as gas-phase precursors. The growth rate of these films was investigated as a function of laser fluence. These measurements, as well as other investigations of film growth with and without the photolysis laser, reveal that no AlN film is produced in the absence of laser-induced photolysis of the precursors. The morphology and physical properties of these laser-grown films have been studied by scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Optical absorption spectra of films grown on fused quartz were measured as a function of substrate temperature. A substrate temperature of 350 K was found to be optimum for obtaining good film quality while precluding any effects due to the thermal decomposition of the precursors. The films have excellent dielectric properties as shown by I-V and C-V measurements. The details of AlN film growth using low-temperature gas-phase photolysis at 193 nm and the characterization of these laser grown films will be discussed.

Copper thin films were selectively fabricated on a Teflon surface by using an ArF excimer laser and a Cu electroless plating solution in open air. Photo-excited C-F bonds of the surface were effectively defluorinated with hydrogen atoms which were photodissociated from the Cu solution. The dangling bonds of the defluorinated carbon atoms were combined with the oxgen and the copper atoms which were also photodissociated. Thus, C-O-Cu bonds were formed on the surface and functioned as Cu nuclei for an electroless plating. The Cu thin films were successfully deposited in electroless plating solution only on the Cu nuclei.

One of the most technologically important uses of organic photochemistry is in the imaging industry where radiation-sensitive organic monomers and polymers are used in photoresists. A widely-used class of compounds for imaging applications are diazoketones; these compounds undergo a photoinduced Wolff rearrangement to form a ketene intermediate which subsequently hydrolyses to a base-soluble, carboxylic acid. Another use of organic molecules in polymer matrices is for dopant induced ablation of polymers. As part of a program to develop diagnostics for laser-driven reactions in polymer matrices, we have investigated the photo-induced decomposition of 5-diazo-2,2-dimethyl-l,3-dioxane-4,6-dione (5-diazo Meldrum's acid, DM) in a PMMA matrix using picosecond infrared spectroscopy. In particular, irradiation of DM with a 60 ps 266 nm laser pulse results in immediate bleaching of the diazo infrared band (v = 2172 cm-1). Similarly, a new band appears within our instrument response at 2161 cm-1 (FWHM = 29 cm-1) and is stable to greater than 6 ns.; we assign this band to the ketene photoproduct of the Wolff rearrangement. Using deconvolution techniques we estimate a limit for its rate of formation of τ < 20 ps. The linear dependence of the absorbance change with the pump power (266 nm) even above the threshold of ablation suggest that material ejection take place after 6ns.