Photoinduced processes on surfaces is of fundamental importance in materials processing. For example, photo-assisted chemical vapor deposition has been used to deposit a number of different materials on solid substrates. The effect of substrate morphology on photoinduced processes can be an important factor in film growth. In order to clarify the role of substrate morphology, in particular surface roughness, on surface photochemistry, we have examined the wavelength dependence of the photodissociation of chlorobenzene and 3-chloropyridine adsorbed on smooth and rough silver surfaces. As discussed below, we have measured a red shift in the photodissociation threshold for these molecules adsorbed on a rough surface relative to a smooth surface. The wavelength dependence of the photodissociation cross-section near the threshold has been measured in order to discern the origin of the red shift.

We extend previous work in broadband synchrotron radiation (SR) excitation of condensed multilayers to the study of reactions driven by monoenergetic SR. The long term goal of this work is to understand the importance of core-level excitation on the reactions that lead to materials growth. Results are presented for two systems of interest: formation of silica from Si(CH3)4 and H20 mixtures with 90 eV irradiation (below the core levels) and the energy dependence of the reaction of SiH4 and H2O.

Laser-induced deposition of controlled quality silicon dioxide and thin metallic films was investigated at 248 nm for phase shifting mask (PSM) repair. SiOx (x-1.5-2) films were deposited from single precursors, such as triethoxyvinylsilane (TEVS), tetraallyloxysilane (TAOS), di-t-butoxy-diacetooxysilane (TBSA) with no oxidizing coreactant. A deposition rate of 0.25 A/pulse was possible at room temperature, with excellent optical properties (n-1.47, k-0.05). Metallic films were deposited from tungsten, gold, molybdenum and chromium compounds. The results showed that the optical transmission and phase-shifting properties of the deposits can be matched well to the films commonly used in phase shifting masks.

Severe excimer laser irradiation is reported to impart electrical conductivity to Kapton* polymide films. We find that a proper choice of pretreatment and irradiation practice reduces the required dose markedly. Such films have sufficient conductivity to permit direct, good-quality, adherent copper electroplating.H.M.Phillips, D.L.Callahan, R.Sauerbrey, G.Szabo and Z.Bor; Appl.Phys.Lett.58, 2761 (1991).

Zinc germanium phosphide, an important frequency-conversion material for producing mid-infrared lasers, is plagued by a defect-related absorption band extending from the fundamental edge (0.62 microns) to ∼3 microns. The level of absorption varies with melt composition, and can be reduced by post-growth annealing treatments. In these experiments, further reduction of the near-band-edge absorption was achieved by irradiating with 1.173 MeV and 1.3325 MeV gamma rays. A 40 kiloCurie “Co source was used to irradiate a series of crystals at an average flux of 4.8x10s rads/hr to cumulative doses up to 3.91xl010 rads. The absorption coefficient in the near-infrared was reduced by nearly a factor of two, and the penetration depth of the ionizing radiation was sufficient to uniformly reduce the absorption in the largest samples tested (up to 7x8x23mm3). The loss coefficients achieved at 1 micron (4.28cm∼l) and at 2.05 microns (0.19cm1) are lower than the best results achievable by conventional thermal annealing alone. No saturation effects or absorption increases at longer wavelengths were observed.

We investigate, for the first time, the possibility to crystallize heavily Ge and C implanted silicon substrates by excimer-laser annealing performed in the molten regime. It is demonstrated that the crystalline quality of the laser grown SiGeC alloys strongly depends on the initial dose of implanted carbon.

In order to search for the possibility to synthesize materials with new functions by laser deposition using source materials consisting of characterized microstructures, the porous silicon was ablated in ultrahigh vacuum with ultraviolet lasers of fluence as low as a few Jem”2. The ablated particles were analyzed by the time of flight method and the main species detected were atoms and small molecules such as Si, SÍ2, and SiO. The kinetics of the laser ablation of porous silicon in comparison with crystal silicon was also studied.

We report for the first time laser-modified chemical beam epitaxy (CBE) of InGaAs/GaAs multiple quantum well (MQW) structures using trimethylindium (TMIn), triethylgallium (TEGa), and tris-dimethylaminoarsenic (TDMAAs), a safer alternative to arsine. X-ray rocking curve (XRC) and low-temperature photoluminescence (PL) measurements were used to characterize the pseudomorphic strained quantum well structures. As determined by the X-ray simulation, laser irradiation during the InGaAs well growth was found to enhance the InGaAs growth rate and reduce the indium concentration in the substrate temperature range studied, 440-S00°C, where good interfaces can be achieved. We attribute these changes to laser-enhanced decomposition of TEGa and laser-enhanced desorption of TDMAAs. With laser irradiation, lateral variation of PL exciton peaks was observed, and the PL peaks became narrower.

The surface morphology and microstructure of (lll)-oriented CeO2 thin films, grown on amorphous fused silica (S1O2) substrates by low-energy-ion-beam assisted pulsed laser ablation, have been studied by atomic force microscopy (AFM) and x-ray diffraction (XRD). These CeO2 films are aligned with respect to a single in-plane axis despite being deposited on an amorphous substrate. There is a honeycomb-like growth morphology to the films and island-growth can be observed in thicker films. These islands, inside of which are high density of honeycomb-like clusters, are separated by a void network with ∼700nm width. However, on the surface of the thinnest film (∼3nm), only very small clusters (diameter <60nm) appear, and the boundaries of the void network are undefined, which implies that the film is just beginning to coalesce into clusters (grains). The combined AFM images and XRD pattern suggest these clusters probably are the initial seeds for the subsequent island growth. Based on these results, the growth mechanism of oriented CeO2 films on amorphous fused silica substrates is discussed.

A parametric study has been performed of amorphous tetrahedral carbon (a-tC) films produced by ion- assisted pulsed laser deposition (IAPLD). The ion voltage, current density, and feed gas composition (nitrogen in argon) have been varied. The resultant films were characterized by thickness, residual stress, Raman spectroscopy, and electrical resistivity. The Raman spectra have been fit to two gaussian peaks, the so called graphitic (“G”) peak and the disorder (“D”) peak. It has been found that the magnitude of the D peak and the residual compressive stress are inversely correlated. At low beam voltages and currents, the magnitude of the D peak is low, increasing as the ion beam voltage and current are raised. The ion beam voltage has the most dramatic effect on the magnitude of the D peak. At low voltages (200–500 V) the magnitude of the D peak is greater for ion beams with high percentages of nitrogen possibly indicative of C-N bonding in the films. At higher voltages (500 - 1500V) the D peak intensity is less sensitive to the nitrogen content of the beam.

We have deposited unhydrogenated diamond-like carbon (DLC) thin films by laser ablation of graphite, using a high power Ti: Sapphire solid state laser system. DLC films were deposited onto single crystal silicon substrates at room temperature with picosecond laser pulses, at peak power densities in the 5x1011 - 8x1012 W/cm2 range. A variety of techniques, including scanning and transmission electron microscopy (SEM and TEM), Raman spectroscopy, spectroscopic ellipsometry (SE), and electron energy loss spectroscopy (EELS) have been used to analyze the film quality. Smooth, partially transparent films were produced, distinct from the graphite target. Sp3 volume fractions were found to be in the 50 - 60% range, with optical bandgaps ranging from 0. 6 to1. 2 eV, depending on the laser power density.

Thin films of polymeric copperphthalocyanine were fabricated via laser assisted molecular beam deposition by reacting the laser ablated plasma flume of a copper target with 1,2,3,5-tetracyanobenzene entrained within a molecular beam expansion. 1,2,4,5-Tetracyanobenzene entrained within a helium carrier gas was supersonically expanded to intercept a second expansion containing gas-phase aggregates of metallic copper. These two molecular beams met at a point between the target and the substrate producing gas phase polymeric copperphthalocyanine which could be then directly deposited as a thin film coating on room temperature substrates. Such films were characterized by scanning electron microscopy and uv-visible, infrared and x-ray photoelectron spectroscopic techniques. Optical spectra of films dissolved in H2S04 solutions reveal that small amounts of monomeric copperphthalocyanine is also present in the grown films. All the copper in these films is found to be in Cu+2 ionization state.

Metal nanocluster composites have attractive properties for applications in nonlinear optics. However, traditional fabrication techniques — using melt-glass substrates — are severely constrained by equilibrium thermodynamics and kinetics. This paper describes the fabrication of metal nanoclusters in both crystalline and glassy hosts by ion implantation and pulsed laser deposition. The size and size distribution of the metal nanoclusters can be modified by controlling substrate temperature during implantation, by subsequent thermal annealing, or by laser irradiation. We have characterized the optical response of the composites by absorption and third-order nonlinear-optical spectroscopies; electron and scanning-probe microscopies have been used to benchmark the physical characteristics of the composites. The outlook for controlling the structure and nonlinear optical response properties of these nanophase materials appears increasingly promising.

Si nanometer structures are promising for exhibiting the quantum size effect at temperatures even as high as a room temperature. The present work investigates by TEM the damages induced by a heavy ion-implantation to the fine Si columns, aim of fabrication of 1-D tunneling PN diode in future. Si columns are fabricated by electron beam lithography and reactive ion etching, followed by thinning by thermal oxidation of Si . Ultra fine Si column with a diameter of 8 nm are successfully formed. TEM lattice image observations for fine Si columns, which are subject to ion-implantation and subsequent annealing, are carried out. In the case of heavy doping of As, as well as BF2, as-doped structure is amorphous, and recrystallization is observed after annealing at 1000 °C for 30 min. Typical damages such as dislocations which are parallel to the {111} planes and Si micro-crystals which are differently oriented from the Si single crystal substrate are observed for Si columns with diameters larger than 40nm. However, it should be noted that no damage is observed for fine Si columns with diameters less than 20nm. It is suggested that defects are diffused out to the surface or the Si/SiO2 interface for ultra fine Si columns during annealing.

Characteristics of polysilicon films, crystallized by excimer laser annealing, have been investigated. The entire amorphous silicon film of 50 mm X 50 mm has been crystallized by scanning a line shape excimer laser beam, which basically reduces the nonuniformity in the beam overlap region of the 2-dimensional scanning method. The laser beam had a Gaussian profile in the scanning direction, which ensured good crystallization by the reversible transitions between the crystalline and amorphous states and was expected to give step annealing effect The laser energy density and substrate temperature were varied.

The stability of laser processed GeSi heteroepitaxial alloys on Si to partitioning driven interface instabilities is examined. Existing stability models are extended to include nonequi-librium solidification effects for nondilute alloys and are examined under typical conditions of laser induced solidification. Ge diffusion and partitioning were measured for quantitative input to the models. The Ge liquid-phase diffusivity was determined to be 2.5 x 10-4 cm2/s. The measured velocity-dependent partition coefficients k(v) were fit to the Continuous Growth Model using an equilibrium k of 0.45 and a diffusive speed of 2.7 m/s. Stability calculations based on these values and our extended stability model are presented. Although instabilities at compositions comparable to those experimentally observed to give defective films are predicted, the growth rates of these instabilities appear too slow to destabilize an interface on laser processing time scales. These results suggest that strain or other effects play an important role in the observed defective microstructures.

It has been shown, that pure massive targets of tungsten and cobalt disilicide can be obtain from the liquid state by means of a set of metallurgical methods. The conditions of laser ablation of the targets ensuring the preparation of tungsten and cobalt suicide films of the specific electric resistance 50 and 30 μΩ cm respectivly have been studied. The grazing beam X-ray difractometry were used to investigate their phase and elemental composition of the films. The method in question has been shown to be promising for the preparation of films of other refractory - metal suicides.

CN1 thin films have been synthesized by ion-beam-assisted laser ablation of graphite. Films with N-concentration of 45% are obtained, indicated by high energy backseattering spectrum (HEBS). Raman and X-ray photoelectron spectroscopy (XPS) data confirm the existence of carbon-nitrogen bonds. Polycrystallites beta-CjNi structure has been detected in the amorphous matrix of the films, as indicated by transmission electron microscopy (TEM) and electron diffraction. Qualitative tests indicate that the films are relatively hard and adhesive.

A method was proposed to generate flat-top polygonal temperature distributions in substrates from a Gaussian-shaped laser source. The original Gaussian beam is equally and diametrically separated into several portions and is then rearranged so that the each portion has its peak intensity allocated toward outside. This can be realized by a symmetrical multi-facet prism. A mathematical model was derived to calculate the temperature rise induced the rearranged portions of the laser beam. Flat-top polygonal temperature profiles with two, three, four and six corners have been investigated by numerical calculations. It is shown that flat-top polygonal temperature distributions can be obtained by this method if the distance between the peaks of the beam portions is arranged to be certain proportions to the original Gaussian beam. It is also found the shape of the temperature profile is almost with the same size as the original Gaussian beam size and does not depend on the incident laser power and the substrate material.