Laser Irradiation Of Films Research Articles

Image analysis of structural changes in laser irradiated thin films of photodeposited a-Se

Write and erase features by the photodeposition effect have been accomplished in recent investigations. Quantitative analysis of the surface grains size and structure in the laser affected areas of the deposited thin films is of importance to the understanding of the material surface redistribution phenomena. Fractal dimensionality and 2D-Fourier spectral analyses have been employed as the most straightforward quantitative approaches connecting the change of grain size distribution with the driving forces involved in the formation of the grain shapes. These approaches have been used since the irregular spatial shapes of the grains cannot be approximated by simple or regular geometrical shapes of definite size. Hence, we use these two topological analysis methods for classifying the surface morphology in the various zones of the laser beam written thin film.

X-ray photoelectron spectroscopy of KrF laser-irradiated polycarbonate films

Spun films of polycarbonate were photoablated in air at 248 nm. The etch and incubation data have a superlinear dependence on the laser fluence. The surface compositional changes were analysed by X-ray photoelectron spectroscopy (XPS). As evidenced by the decrease of the O/C ratio, photoablation is inferred as distinct from the low-intensity photooxidative degradation. A direct correlation is observed between the XPS and incubation data and the ablation seems to occur by chain scission at the CO bond, the fully incubated surface being an average of monomeric composition.

Effect of laser irradiation on structural, electrical and optical properties of SnO2 films

Thin films of SnO2 were prepared using a spray pyrolysis technique. Films were irradiated with Nd:YAG laser pulses of various energy densities (2–50 mJ cm−2) with varying number of pulses from 1–50. X-ray diffraction studies were made to investigate the structural changes due to laser irradiation. An improvement in crystallinity and an increase in grain size were observed in laser-irradiated films. Hall coefficient and Hall mobility studies were made in the temperature range 77–300 K for the as-grown as well as laser-irradiated films. An increase in mobility and a decrease in carrier concentration were observed in the films after laser irradiation. Optical transmission studies revealed that the refractive index increased as a result of laser irradiation.

Laser marking of thin organic films

The threshold marking response of a laser-irradiated dye-polymer thin film is described by a simple, thermally thresholding model. The apparent loss of thermal reciprocity is related to active reflectance changes during mark formation. It is shown that incorporation of measured differences between physical and optically detected mark lengths are required for the model to accurately replicate the subsequent marking response. A theoretical expression is derived that permits the estimation of media thermal diffusivity from the measured marking response.

Ｚｎ／Ｎｉ二層めっき皮膜の表層合金化に及ぼすＣＯ２レーザ処理の影響

A new method of Zn-Ni alloy coating has been developed in which Zn/Ni double coated films were electroplated onto steel substrates, and then irradiated by a high-power CO2-laser to alloy the Zn/Ni.Alloying conditions of the laser-irradiated films were then examined. X-ray diffraction analysis revealed that the irradiated films were of the Ni5Zn21 (γ-phase) structure. EPMA line analysis showed that the surface of the irradiated films was produced by diffusion from the Ni in the underlying film to the surface of the Zn overlying film.This demonstrated the utility of alloying Zn/Ni double coated films by CO2-laser irradiation.

Excellent thermal stability of superconducting properties in YBa2Cu3O7 films irradiated by pulsed excimer lasers

We have investigated the microstructure and superconducting properties of YBa2Cu3O7 films irradiated by nanosecond pulsed excimer lasers. The superconducting YBa2Cu3O7 thin films were deposited in situ on (100) LaAlO3 substrates using the pulsed laser evaporation technique. The virgin unirradiated YBa2Cu3O7 films exhibited excellent superconducting properties with Tco (temperature for zero resistance) of 90 K and critical current densities Jc (at 77 K and zero magnetic fields) of approximately 5.0 × 106 A/cm2. The films were further irradiated by a pulsed excimer XeCl laser (λ=308 nm, τ=45×10−9 s) with energy density varying from 30 to 300 mJ/cm2. Excellent thermal stability was observed for YBa2Cu3O7 films on LaAlO3 substrate for laser irradiation at all energy densities between 30 and 300 mJ/cm2, with no deterioration in the Tco values (90±0.3 K). An improvement in the Jc of the films was observed at low-energy density irradiation, however, for energy densities above the melt threshold the Jc values decreased sharply. The Raman measurements for laser irradiated films showed improvement in the crystallinity of the film with stronger Raman peaks at 140 and 340 cm−1, thus correlating the improvement in Jc to better crystallinity of the films.

Substrate Surface Effects on the Properties of Sputter-Deposited and Laser-Irradiated Films.

ABSTRACTSapphire substrates, mechanically polished to an optical finish, were annealed for two days at either 1000°C or 1350°C. The near surface condition of as-polished and of the annealed substrates was analyzed by Rutherford backscattering/channeling (RBS-C) and by scanning electron microscopy/channeling (SEM-C), by transmission electron microscopy (TEM), and by scanning tunnelling microscopy (STM). The polished substrates were found to be RBS-amorphous up to 100 nm, and heavily damaged at larger depths. In agreement with these results, no electron channeling was obtained from polished samples. TEM, however, showed that the damaged region was crystalline, and the only defects detected were microtwins. Both RBS-C and SEM-C analyses revealed that the damage is removed when the sapphire substrates are annealed for 48 hrs. at 1350°C. The condition of the near-surface region, viz., as-polished or annealed, is found to strongly affect the morphology of the laser-irradiated copper films deposited on sapphire substrates. A correlation is found between the threshold for film evaporation and for film rupture upon laser irradiation, both being a function of the substrate condition. It is concluded that the near-surface damaged layer acts as a thermal barrier for heat transport across the substrate.

Excimer Laser Irradiation of Metallic Films on Ceramic Substrates

ABSTRACTCopper films sputter deposited on mechanically polished (optical finish) and on annealed substrates were laser-irradiated at various energy densities. The effect of the substrate condition on both the evaporation threshold and the morphology of the laser-irradiated metallic films was investigated. The energy density threshold for laser-induced evaporation of the copper films was studied using energy dispersive x-ray spectroscopy (EDS) in a scanning electron microscope (SEM). It was found that for annealed substrates the energy density threshold decreases relative to the threshold for the as-polished condition. These results are compared with predictions of a mathematical model that assumes that the near surface region of the as-polished ceramic is a highly damaged region and, thus, constitutes a thermal barrier. The film remains intact and with almost no change in morphology after laser irradiation at energy densities lower than 0.80 J/cm2 if the substrate has been previously annealed. On the other hand, copper films deposited on as-polished substrates break up during laser processing forming copper islands.

Through-thickness mark length variations in laser-irradiated thin films

Low-conductivity, laser-irradiated thin films such as the chalcogenides employed for optical data storage can display manifestations of significant through-thickness thermal gradients. A combined Laplacetra nsform, Fou rier-i nteg ral method was used to derive the tern peratu re distributions in such films, and the results were used to examine the effects of some marking parameters on through-thickness thermal gradients. The results were in good qualitative agreement with experimental observations.

Thermocapillary Effects in Laser Direct-Write Metallization

AbstractA 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.

Crystallization of TeOx-Pd Films for Optical Recording Materials

The crystallization of TeOx-Pd films has been studied by differential thermal analysis, X-ray diffraction and transmission electron microscopy. The optical transmittance changes accompanying crystallization are not monotonous, but stepwise with increasing annealing temperature. The changes in films annealed at temperatures lower than 270°C are based on the phase transformation of PdTe from the amorphous to the crystalline state without large grains. For the films annealed at temperatures up to 270°C, large crystal grains of PdTe are observed. On the other hand, no large crystal grains in the recorded spots by laser irradiation are observed though the laser power is increased up to the level sufficient to melt the films. The degree of crystallization in laser-irradiated films is the same as that in films annealed at 270°C.

Crystallization of hydrogenated amorphous silicon films by pulsed ruby laser irradiation

We observe that the hydrogenated amorphous silicon (a-Si:H) films deposited by glow discharge method on Corning glass are transformed from the amorphous to crystalline state by the ruby laser irradiation. Raman scattering, X-ray diffraction and Nomarski optical microscopy are carried out on the laser irradiated Si films. Raman spectra of the irradiated Si films have the peak at 520 cm -1 just like single or polycrystalline Si. From X-ray diffraction linewidths and Nomarski micrograph of the irradiated films, the estimated grain size is 1 μm.

Generation and detection of 160 MHz acoustic waves using a TEA CO/sub 2/ laser irradiated polymer film combination

High-frequency (~160 MHz) large-amplitude acoustic waves have been generated by irradiating a thin polymer film with a spontaneously mode-locked TEA (transversely-excited atmosphere) CO(2) laser and detected using a wide-bandwidth piezoelectric polymer transducer. This approach uses a simple and commonly available infrared laser, does not require special coatings to be deposited on the acoustic generating surface, and is inherently simple in its design and operation.

Stabilization of GeO phase on n-Ge and laser irradiated Ge films

XPS and XAES study of oxidation of Ge has shown that the GeO phase can be stabilized on n-Ge and laser irradiated Ge films.

New Fluorescence from Molecular Aggregates of 10-(1-Pyrenyl)decanoic Acid

Abstract In addition to the normal monomer and excimer fluorescence, vacuum-deposited, cast and their laser-irradiated films of 10–(1-pyrenyl)decanoic acid showed three kinds of fluorescence bands. Similar new fluorescence bands were also observed in its aqueous solution. These emissions were due to meta-stable aggregates of pyrenyl chromophores whose structures were ascribed to molecular interactions operating during the processes of film preparation.

Picosecond Transient Reflectance Measurements of Crystallization In Pure Metals

ABSTRACTThe kinetics of rapid crystallization in metals is investigated by measuring transient optical property changes in laser irradiated gold and copper films in the picosecond and nanosecond regimes. Melt thresholds are determined by examining concentration profiles of multi-layered films before and after irradiation.

Possibility of self-epitaxial growth of laser irradiated AlSb films

Metallic films of alternating Al and Sb layers are laser pulse irradiated at room temperature in air in order to obtain the semiconducting compound AlSb. Using transmission electron microscopy and high resolution electron diffraction, the crystal growth is studied as a function of the spatial distribution of the laser beam. It is shown that by monitoring the beam inhomogeneities in an easy manner, it is possible to control the crystallite’s size, which may be 50 times the total thickness of the film. The possibility of a self-epitaxy without substrate is also demonstrated.

Substrate Latent Heat Effects in The Calculations for Pulsed Laser Irradiated Thin Films

ABSTRACTWe present a numerical model for the calculation of the temperature rise caused by pulsed laser irradiation of a thin film/substrate structure. This model includes phase changes in both the thin film and the substrate. The inclusion of phase changes results in more complex thermal behavior and significantly affects melt durations. This model was applied to the AuGe/GaAs system. Morphological observation using the scanning electron microscope and SIMS profiles provides experimental verification for the numerical calculations.

Preparation of GaAs Soi and its Laser Recrystallization

ABSTRACTGaAs SOI consisting of a sputtered GaAs film on a SiO2 −Si or sapphire substrate is irradiated by CW Ar+ laser beam with a view to investigating its recrystallization. Using AES, x-ray diffraction, TEM and ED, we have studied the compositions, crystal orientations and grain size of the laser-irradiated GaAs films. The possible application of GaAs SOI to devices is discussed on the basis of the experimental results.

5354. The effect of thermal annealing on the grain size and electrical characteristics of arsenic ion-implanted and laser-irradiated polycrystaliine silicon films: Kenji Shihata and Shinji Onga,J Appl Phys52 (9), 1981, 5566–5574

5354. The effect of thermal annealing on the grain size and electrical characteristics of arsenic ion-implanted and laser-irradiated polycrystaliine silicon films: Kenji Shihata and Shinji Onga,J Appl Phys52 (9), 1981, 5566–5574