Nanocrystalline self supporting thin films of Ni, Co, Cr, V, and Ti were irradiated with 600 keV Xe ions at liquid nitrogen temperature and the resulting grain growth was measured by transmission electron microscopy. Average grain sizes were seen to increase from about 10 nm to 18–35 nm, depending on the metal. Systematic variations did not support current thermal spike models.

We have used 2-MeV and 200-KeV He implantation into KNbO3 and LiNbO3 single crystals to generate a damaged layer of reduced optical index. MeV implantation enables the formation of optical waveguides of several µm thickness, which have been analyzed by dark and bright line spectroscopy in order to determine the refractive index profiles. In addition, 200-keV implants have been used to model the end-of-range-damage, which was measured by RBS/Channeling. KNbO3 and LiNbO3 show a distinctly different sensitivity of the radiation damage.

The in situ ion irradiation capability of Argonne’s HVEM-Tandem User Facility has been employed to study effects of 1.5 MeV Kr+ irradiation and 300 kV electron irradiation on the crystallization of as-deposited and of partially crystallized 40 nm thick films of CoSi2. Ion fluxes ranged from 8.5×1014 to 6.8×1015 m−2s−1 for which beam heating effects may be neglected. The maximum electron flux at 300 kV was 0.8×1023 m−2S−1. The maximum temperature at which crystalline CoSi2 is amorphized by the ion irradiation of flux = 6.8×1015 m−2s−1 is between 250 and 280 K. At higher temperatures amorphous material crystallizes by growth of any preexisting crystals and by classical nucleation and growth, with radial growth rates which are proportional to ion flux. The average degree of transformation per ion is 4×10−26 m3 per ion. Thermally induced crystallization of as-deposited films occurs above approximately 420 K. For ion doses at least as low as 3.4×1016 m−2 ion irradiation at 300 K promotes thermal crystallization at 450 K, by virtue of enhanced apparent nucleation and at large doses, by enhanced growth rate.

The coarsening of CoSi2 precipitates and the microstructural evolution of (111) Si implanted with 200 keV Co+ ions at 350°C and fluences of 1×1016cm−2 and 6×1016cm−2 were investigated as a function of depth, annealing temperature and annealing time using Rutherford Backscattering Spectroscopy (RBS) and Transmission Electron Microscopy (TEM). After annealing cross-section TEM micrographs show a layered array of platelet-shaped precipitates with preferred facets on {111} planes. The fraction of Co-atoms, that were redistributed during the different annealing temperatures and times, has been used to determine an activation energy for the precipitate coarsening. By applying the Meechan-Brinkman and the change-of-slope methods, we obtained activation energies in the range of 3.2 – 3.6 eV.

High dose zinc implantation (1×1016 to 6×1016 ions/cm2) into c-axis sapphire at 770K produces amorphous surface layers. Post-implantation annealing at temperatures at and above 800°C show that the modes of recrystallisation are strongly dependant on ion dose. At low doses formation of crystallites of α and γ phase Al2O3 is seen, with no evidence of any planar epitaxial growth at the original crystalline-amorphous interface. The zinc is seen to diffuse isotropically within the crystallised layer and becomes partially substitutional within the crystallites. At high doses, however, the formation of crystallites is inhibited, with the layer remaining amorphous. A more rapid diffusion of zinc is seen in the amorphous Al2O3, with some of the zinc being lost at the surface.

The laser-target interactions during pulsed laser evaporation (PLE) of materials have been investigated in detail. Sub-surface temperatures have been calculated to be higher than the surface temperatures during planar surface evaporation of the target material. While the evaporating surface is being cooled due to the latent heat of vaporization, sub-surface superheating occurs due to the finite absorption depth of the laser beam. Detailed computer simulations have been carried out to understand the evaporation characteristics of different targets (Si, YBa2Cu3O7 ) as a function of laser and target variables. For silicon targets irradiated with 25 nanosecond laser pulses (energy density of 10J/cm2, absorption coefficient of 105 cm−1), the sub-surface temperatures were found to be more than 2000°C above the surface evaporation temperatures. The sub-surface superheating increased with increasing energy density and absorption depth. This internal superheating effects may lead to volume evaporation of the target where a solid material in form of particles may be ejected from the target surface. Based on the above understanding, parameters required to reduce the particle density in PLE films are predicted.

The focused output from a copper laser (λ = 510nm) has been used for direct writing of Al on silicon substrates by pyrolitical decomposition of trimethilaluminum (TMA). These results demonstrate that direct writing can be accomplished at room temperature by a single-step deposition process induced by a single light source. For a laser power density between 5 and 50 kW cm−2, the widths of the stripes varied between 60 and 200 μm with corresponding thickness between 0.5 and 0.8 μm. The width of the stripes proved to be independent of the scanning velocity, Vs, within the range 50 μm s−1 < Vs < 300 μm s−1. The analysis included scanning electron microscopy (SEM) to study the film morphology, a step profiler to evaluate the thicknesses and the profiles of the stripes, and energy dispersive spectroscopy (EDS) to provide their chemical compositions.

Three-elements (In-Sb-Se) alloy thin films are synthesized by laser irradiation of multi-layered films. Optical characterization of the films is performed function of laser fluence which helps defining optimized conditions for the production of good quality, homogeneous alloy films. Such films exhibit particularly high reflectiviy contrast (4:1) for the alloy SeSb2 25 In1.75·.

Radiation heat transfer has been found to have the greatest Impact on the quality of the thin recrystalllzed silicon film during zone-melting recrystallizatlon (ZMR) processing. This study focused on the radiation effects during ZMR with an Infrared radiant line heat source such as a graphite strip heater. The multilayer nature of the capped sllicon-on-tnsulator (SOI) structure Induces complex optical effects which affect the temperature distribution during processing. A two dimensional numerical model of the ZMR process has been developed using a finite difference scheme. The effect of the radiant line heat source’s emission into the wafer has been modeled with a matrix method using Fresnel coefficients. A numerical parametric study was conducted to observe the effects of varying the thickness of the different layers In a capped SOI wafer on the maximum temperature and melt width attained. Results indicate that the variation of either the capping or insulating silicon oxide layer causes significant fluctuations of the reflectivity and temperature profile of the film. Increasing the thickness of the Si layer results in a nearly linear increase in temperature and melt width after complete melting. Layering schemes that are sensitive to small variations In thickness that may result in large changes in reflectivity were Identified.

Selective surface modification of fluorocarbon resin has been demonstrated by using an ArF excimer laser beam and an ammonia complex which was made from NH3 and B2H6 gases. The fluorocarbon resin was set in the atmosphere of NH3 gas. NH3 molecules which were adsorbed on the surface reacted quickly with the B2H6 molecules, and an ammonia complex was produced. As a result, the complex was adsorbed on the surface. The resin surface was selectively irradiated by ArF laser beam. The complex and C-F bonds of this resin were excited by the laser beam, and the surface was selectively modified to be hydrophilic property. The modified samples were evaluated by XPS analysis, measuring the contact angles of the water and the SEM image on the surface.

Thermally labile involatile inorganic complexes and biomolecules have been laser desorbed from silver doped emulsions without significant fragmentation. The silver doped emulsions are saturated with the molecule of interest and then mounted in the source chamber of a skimmed molecular beam apparatus. A pulsed frequency doubled Nd:YAG laser is used to desorb the molecules. The desorbed molecules are entrained in a pulsed supersonic expansion of argon, and are thereby cooled rotationally and vibrationally. A pulsed tunable dye laser is used to ionize the desorbed molecules (either resonantly or non-resonantly) between the acceleration grids of a Wiley-McLaren configuration time-of-flight mass spectrometer. Mass-resolved detection of the ions created from the desorbed species reveals that the desorption process causes almost no fragmentation for all the species studied (various aromatic amino acids and inorganic coordination compounds such as the [Ru(2,2’bipyridyl)3] moiety). While other techniques are successful for introducing relatively involatile materials into mass spectrometers, they often lead to substantial fragmentation of the molecular species of interest. Laser desorption combined with laser ionization can minimize fragmentation during both the vaporization process and the ionization step. Furthermore, a specific merit of our sample handling technique involving silver doped emulsions is that the number density of desorbed species is found to remain sufficiently stable on a shot-to-shot basis so as to permit the recording of wavelength scanned resonance enhanced multiphoton ionization spectra. The combination of laser desorption with resonance enhanced multiphoton ionization spectroscopy has thus provided for the first time a means of recording electronic spectra for a range of vibrationally and rotationally cooled involatile materials.

Maskless patterning of alumina (A12O3) films of various thicknesses and ceramic (TiC-Al2O3) substrate material was accomplished by using pulsed excimer and Nd:YAG laser systems. Etched structure size was defined through the computer software which also controls the workpiece position and laser operating parameters. Etch profile, materials removal rate and surface roughness was found to be dependent on laser emission wavelength, fluence, pulse rate and relative scan speed. Smoother etching was obtained with the excimer lasers. The etch characteristics are compared with those of the polymeric and metallic materials. Various potential applications of this laser based etching process in microelectronic and micromagnetic device fabrication are identified.

The excimer-laser-assisted etching of GaAs in Cl2 at 308 nm has been studied as a function of substrate temperature in the range of 23 to 150°C. Rectangular channels were etched into (100)-oriented, undoped GaAs wafers. The fluence from the xenon chloride excimer laser at the GaAs surface was 175 mJ/cm2. At temperatures below 75°C, the etch rate was independent of substrate temperature and the etch rate increased with Cl2 pressure from 0.4 to 2.0 Torr. At substrate temperatures above 75°C, the etch rate increased with increasing substrate temperatures and was independent of Cl2 pressure. Analysis of the temperature dependence of the total etch rate above 75°C according to an Arrhenius expression gave an activation energy of 11.8 kcal/mol, which is consistent with the enthalpy of vaporization of GaCl3. The onset of the temperature dependent region coincides with the melting point of GaCl3.

Photoexcitation of the Si electronic subsystem during ion implantation was found to be able to control radiation damage accumulation. Conditions when additional light illumination during ion bombardment suppresses radiation defect formation are determined. The model of effect observed taking into account recombination of nonequilibrium electron and holes is proposed. Coefficient between the change in amount of damage accumulated and the rate of nonequilibrium charge carriers generation is estimated.

Threats of lasers to human eyes and electro-optics on the modern battlefield has been significantly increased due to the rapid growth of laser technology in military applications. Currently polycarbonate (PC) and poly [methyl methacrylate] (PMMA) are being used as transparencies for aircraft and goggle materials for aircrews and combat soldiers [Ref 1,2]. A carefully monitored laser test was conducted on these two particular polymers using a medium-power, continuous-wave CO2 laser to determine the brightness of the laser-induced plume radiance and how much luminance was transmitted to the back of the sample. Plume luminance for photopic (daytime) and scotopic (nighttime) visual conditions, as well as the recovery times for human eyes exposed to these levels of luminance were calculated. Our test results demonstrated that the plume induced by the CW CO2 laser irradiation can be an ocular hazard to soldiers operating behind these conventional transparent materials.

A pulsed excimer laser was used to ablate aluminum metal into an oxygen-containing atmosphere. The resulting fine powder was collected on a 0.1 μm filter and analyzed to determine structure and composition. Using a combination of TEM, EELS, and thermal analysis techniques, the product was found to be amorphous aluminum oxide, Al2O3. The morphology of the powders was investigated using SEM, TEM, and surface area measurements. The resulting powder was crystallized and examined by x-ray diffraction.

A model describing melting and thermocapillary (or Marangoni) flow in laser irradiated thin films is presented. The free surface formulation leads to predictions of surface profiles that are in qualitative agreement with experimental observations. Additional experimental results for direct-writing of palladium from palladium acetate films demonstrate the influence of thermocapillary effects on the dynamics of the process.

We have theoretically and experimentally investigated the dynamics of the evaporated material generated by nanosecond excimer laser irradiation of YBa2Cu3O7 targets in vacuum. The velocity distribution and the ionization of the plasma were determined by the ion time of flight measurements. The excimer laser ablated species possessed very high velocities (> 106 cm/sec) which increased non-linearly with energy density. The ionization/ volume of the evaporated material exhibited a weak dependence on energy density, thereby suggesting the role of nonthermal mechanisms in the ionization process. These experimental results have been correlated with the theoretical model analyzing the plasma dynamics during pulsed laser evaporation of materials. A new modification to the earlier theoretical model is developed which accurately predicts the terminal velocities and the effect of ionization on these velocities. Various factors including, evaporation rates, degree of ionization, and laser wavelength which affect the plasma velocities will also be discussed.

We have investigated laser ablation of excited atoms from the ferroelectrics LiNbO3 and KNbO3 at 308 nm. Comparisons of the yields for O*, K* and Nb* from pure and undoped KNbO3 show the effects of changing intensity, surface condition and irradiation time on the yield of excited atoms. Below about 20 GW cm−2, the mechanisms for production of excited atoms differ among the various species; above that intensity, the production of a dense electron-hole plasma appears to impart a collective character to the ablation mechanism.

Speed distributions were determined for the ions ejected from MoS2 by excimer laser ablation. It was found that the majority of ionic species were atomic and were ablated with speeds in excess of 6 km/s. The speed distributions were found to be non-Maxwellian and were best described by a supersonic expansion model. The differences in ArF and KrF excimer laser ablation are discussed.