Effects Of Excimer Laser Irradiation Research Articles

Exploring UV-Laser Effects on Al-Implanted 4H-SiC

In this paper, we explore the effects of excimer laser irradiation on heavily Aluminum (Al)-implanted silicon carbide (4H-SiC) layer. 4H-SiC layers were exposed to UV-laser radiation (308 nm, 160 ns), at different laser fluences and the effects of the laser exposure surface were evaluated from morphological, micro-structural and nano-electrical standpoints. Depending on the irradiation condition, significant near-surface changes were observed. Moreover, the electrical characteristics of the implanted layer, evaluated by means of transmission line method, gave a sheet-resistance of 1.62×104 kW/sq for the irradiated layer, linked to a poor activation of the p-type dopant and/or a low mobility of the carriers in the laser-modified 4H-SiC layer. This study can be useful for a fundamental understanding of laser annealing treatments of 4H-SiC implanted layers.

Effects of Excimer Laser Irradiation on the Morphological, Structural, and Electrical Properties of Aluminum-Implanted Silicon Carbide (4H-SiC)

Effects of Excimer Laser Irradiation on the Morphological, Structural, and Electrical Properties of Aluminum-Implanted Silicon Carbide (4H-SiC)

The effect of excimer laser irradiation on mid-IR spectra of mineral mixtures for remote sensing

We examined the influence of micrometeorite bombardment simulated with an excimer laser, which irradiated mixtures of minerals with an energy density between 1.9 J/cm2 and 3.3 J/cm2. As starting material for the mixtures, we selected a natural olivine (Fo91) and a natural pyroxene (En87). Olivine and pyroxene are important rock-forming minerals of Earth's upper mantle and also occur on other terrestrial planetary bodies. The minerals were used to prepare a compositional range of mixtures that were pressed into pellets and examined especially by diffuse reflectance mid-infrared spectroscopy to identify changes caused by micrometeorite impacts as one tracer of space weathering on airless bodies such as Mercury or Moon. Spectral mid-IR measurements were carried out on untreated and treated samples in high vacuum. For comparison, the untreated samples are investigated in low vacuum under various phase angles. Especially the spectral variation between 7 μm–14 μm is of interest as the most important mid-IR features of rock-forming minerals as the Christiansen feature, Reststrahlen bands, and Transparency feature are located in this spectral region.As a result, we found that the mid-IR spectra of the powder pellets show signs of agglutination after irradiation. Here, olivine demonstrates a larger effect on irradiation than pyroxene, whereby pyroxene in mixtures can mask the presence of olivine in the mid-IR spectra after micrometeorite bombardment. We also observed a shift of the CF to longer wavelengths (shorter wavenumbers) after irradiation, and from high to low vacuum, a modification more prominent in olivine than in pyroxene. Therefore, this study shows that the identification and quantification of minerals in mixtures solely on the base of the CF location of the respective material can lead to an overestimation of modal abundances, which is important for the interpretation of data coming back from space missions, e.g., from the MERTIS experiment onboard BepiColombo.

Excimer laser annealing method for achieving low electrical resistivity and high work function in transparent conductive amorphous In2O3:Zn films on a polyethylene terephthalate substrate

We have developed an excimer laser annealing method to achieve low electrical resistivity (ρ) and a high work function in amorphous In2O3:Zn (IZO) films on polyethylene terephthalate (PET) substrates. The effect of excimer laser irradiation of the films on crack formation, electrical properties (ρ, carrier concentration, and Hall mobility), and work function were investigated. KrF excimer laser irradiation produced cracks in the surface of the IZO films on PET as a result of thermal expansion of the PET substrate. By inserting an amorphous SiO2 layer as a heat barrier between the IZO layer and PET substrate, crack formation was prevented. Moreover, it was found that the work function of IZO film could be controlled by the laser fluence and repetition rate. Irradiation of a 150-nm-thick amorphous IZO film on a SiO2-coated PET substrate achieved a low ρ of 3.55 × 10−4 Ω cm and a high work function of 5.4 eV due to the reduction of oxygen and carbon while maintaining a flat surface.

Effects of excimer laser irradiation on the expression of Th17, Treg, TGF-beta1, and IL-6 in patients with psoriasis vulgaris

The effects of laser irradiation on the expression of T helper 17 (Th17) and regulatory T (Treg) cells and their related cytokines, transforming growth factor beta 1 (TGF-β1) and interleukin-6 (IL-6), respectively, in the peripheral blood of patients with psoriasis vulgaris were investigated. 38 patients with psoriasis vulgaris in the stable state were selected as the treatment group that was treated twice a week for eight weeks. Another 38 healthy persons were chosen as the control group. Before and after treatment, the percentages of Th17 cells and Treg cells in the patients’ peripheral blood were detected using flow cytometry, the content of TGF-β1 and IL-6 in the patients’ sera were detected using enzyme-linked immunosorbent assay, and the extent and severity of lesions were determined by weighing the psoriasis area and severity index (PASI). After laser treatment, the percentage of Th17 cells, the Th17/Treg cell ratio and the level of IL-6 in the peripheral blood of patients with psoriasis in the treatment group were significantly lower than those of the same patients before the treatment (P < 0.01), while the percentage of Treg and the content of TGF-β1 in the patients’ sera were significantly higher than before the treatment (P < 0.01). The effective rate for laser irradiation of psoriasis vulgaris was 84.21%, and the PASI score was significantly lower (P < 0.01). Excimer laser irradiation can positively affect the Th17/Treg cell ratio and the expression of related cytokines in the peripheral blood of patients with psoriasis vulgaris.

准分子激光照射对寻常型银屑病患者外周血Th17/Treg失衡及相关细胞因子表达的影响

准分子激光照射对寻常型银屑病患者外周血Th17/Treg失衡及相关细胞因子表达的影响

不同气氛下ZnO薄膜的准分子激光辐照效应

不同气氛下ZnO薄膜的准分子激光辐照效应

Effect of excimer laser irradiation on crystallinity and chemical bonding of biodegradable polymer

The biodegradable polymer such as poly( l-lactic acid) (PLLA) is promising in drug delivery applications because its chemical structure allows it to hydrolyze into non-toxic substances in the human body. In such applications, drugs are embedded in a polymer matrix and released at the rate at which it degrades. PLLA degradation rate is a strong function of its crystallinity. Thus, control over crystallinity allows for continuous modification of drug release profiles. The excimer laser is used in this study to induce surface crystallinity changes because its spatially uniform intensity profile is favorable for surface treatment. The effects of excimer laser irradiation on the surface morphology, crystallinity, and chemical modifications are investigated via optical microscopy, wide-angle X-ray diffraction, and X-ray photoelectron spectroscopy. A model is developed to numerically examine the spatial and temporal temperature profiles, as well as the amount of chemical modifications. It is found that PLLA crystallinity decreases as a function of laser fluence, and that the amount of chemical modifications is minimized by annealing before laser treatment and reducing laser fluences, which decrease free radical mobility and thus the dissociation quantum yield. A working window is demonstrated in which PLLA crystallinity decreases with no measurable chemical modifications, and the working window can be enlarged by decreasing free radical mobility.

Comparison of the effect of excimer laser irradiation and RF plasma treatment on polystyrene surface

Polystyrene (PS) samples were treated with excimer laser, argon and oxygen plasmas. The surface of PS was irradiated using ArF excimer pulsed laser ( λ=193 nm). Radio frequency glow discharge (RF) was used to generate the argon and oxygen plasmas. The samples were processed at different number of pulses and treatment times. The changes were characterized by atomic force microscopy (AFM), attenuated total reflectance Fourier transform infrared (ATR-FTIR), scanning electron microscopy (SEM) and contact angle measurements. The data from ATR-FTIR spectra showed the induction process of oxygen-based functional group in both PS samples treated with RF plasma and laser. AFM and SEM observations demonstrated that a specific nanostructure was created on the laser-treated PS surface. Contact angle measurement indicated higher wettability of the treated PS with both argon and oxygen plasmas and lesser wettability of laser-treated samples. The data from in vitro assays showed the significant cell attachment and growth onto plasma-treated surfaces in comparison with laser treated samples.

The effects of excimer laser irradiation at 248 nm on the surface mass loss and thermal properties of PS, ABS, PA6, and PC polymers

AbstractExcimer laser irradiation provides a new and important method for polymer surface treatment. In this work, the weight loss of engineering polymers PC, ABS, PS, and nylon 6 were investigated following irradiation by KrF excimer laser. The experimental results revealed that the polymeric weight loss is nonlinearly related to the laser energy and laser frequency for most of the materials tested. The effects of laser irradiation on the thermal properties (Tg or Tm) of the polymers were investigated using DSC. It was found that the Tg and Tm of these materials decreased as a result of laser treatment, indicating the degradation effect of the laser irradiation procedure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1024–1037, 2006

Characterization of enhanced emission from excimer laser treated ZnO ceramics using one- and two-photon luminescence spectroscopy and microscopy

The effects of excimer laser irradiation on the surface structure and luminescence of sintered ZnO ceramics were investigated. Photoluminescence spectra of three materials (as-prepared ZnO ceramic, the ceramic blackened by high-energy irradiation and the recovered ceramic treated using lower-energy irradiation) were compared in the visible region at room temperature and 10 K. Each material exhibited a green luminescence band but the blackened ZnO ceramics had the strongest emission in the visible region while the recovered ceramics had significantly shorter decay times.

Effect of excimer laser irradiation on polycrystalline GaN

Polycrystalline GaN films grown on silica substrates by metalorganic chemical vapor deposition were irradiated by a KrF excimer laser. As the laser energy density increased, it was observed that the surface became smoother and the GaN grain size became larger. Band-edge (BE) emissions were found to become stronger at higher laser energy densities whereas yellow luminescence (YL) emissions were unchanged. It was thought that the laser irradiation had a significant effect on the BE emissions which strongly depended on surface morphologies, but no effect on the YL emissions which originated from the entire GaN film due to a shallow irradiation depth.

Comparison between excimer laser irradiation effects in FeCr-based metallic glass and stainless steel

Pulsed excimer laser (248 nm, 8 ns) irradiation of Fe77Cr2B16Si5 metallic glass produces an out-of-plane reorientation of magnetic moment directions as well as changes in the resonant area of the Mössbauer spectra which depend on the irradiation time. Scanning electron microscopy (SEM) determinations linked these changes to the occurrence of molten zones subsequently resolidified. For comparison, Mössbauer spectra of the Fe/Cr18/Ni8/Ti magnetic steel showed additional features in the probability distribution of the hyperfine magnetic field, while the distribution of the Fe/Cr18/Ni8/Mo3 nonmagnetic steel remained unchanged after laser processing. For both steels, the distribution area in the Mössbauer spectra was found to decrease steadily as a function of irradiation time and the magnetic hyperfine fields showed maxima after 10 s/spot. SEM/EDX examination of the laser irradiated areas demonstrated that Ti atoms are displaced from these zones and suggest atomic rearrangements related to the features observed in the distributions of probability.

ArF excimer laser irradiation effects in AlF3-based fluoride glasses for vacuum ultraviolet optics

Color center formation in AlF3–YF3–RF2 (R=alkaline earth metal) glasses doped with PO2.5 (0–3 mol %) by irradiation with ArF excimer laser light was examined by optical absorption (vacuum ultraviolet–visible) and electron paramagnetic resonance (EPR) spectroscopies. Concentrations of impurity iron in all the glasses and oxygen in the P-free samples were ∼0.2 and ∼450 ppm, respectively. Optical absorption ranging from 2–8 eV was induced via one-photon absorption processes. The optical band dominating the transmission loss at 193 nm has a peak at 5 eV in the P-free glasses or a peak at 6.9 eV in the P-doped glasses. The origins of the 5 and 6.9 eV bands were tentatively ascribed to an oxygen-related hole center giving an EPR signal with a width of 7.2 mT at g=2.0097 and P E′ center giving a hyperfine doublet with a separation of ∼70 mT. Provided these correspondences, then the values of oscillator strength for the 5 and 6.9 eV bands were calculated as ∼0.15 and ∼0.1, respectively. No formation of color centers associated with intrinsic constituents such as Al, Y, R, and F ions, was observed. The present results suggest that the reduction of impurity oxygen content is a route to effectively suppress the solarization in the P-free AlF3-based glasses.

Electrical Properties of a Semiconducting Layer Formed on SrTiO3 Single Crystal by Excimer Laser Irradiation

Effects of excimer laser irradiation on electrical properties were investigated for insulating SrTiO3 single crystals, and the mechanism was discussed. A drastic drop of surface resistance from >1013 Ω/cm2 to about 104 Ω/cm2 was observed after irradiation by KrF and XeCl laser light with fluences of about 100 and 200 mJ/cm2, respectively. For laser irradiation with a fluence above these critical values, the surface resistance remained at almost the same, low values. Traces of local melting, in the form of microcracks, were recognized on the surfaces with low resistance. The low-resistance surface had n-type semiconductivity, and the resistivity, electron concentration and mobility were estimated to be 0.2 Ωcm, 5.4×1018 cm-3, 5.4 cm2V-1s-1, respectively, by the Hall coefficient measurement assuming a semiconductive layer thickness of 0.3 µm. On the basis of the result of X-ray photoelectron spectroscopic analysis, the drastic decrease in resistivity is attributed to the generation of oxygen vacancies.

Laser surface modification: structural and tribological studies of AlN coatings

In order to improve the superficial wear resistance and hardness of aluminium substrates, aluminium nitride AlN coatings were elaborated by laser-induced plasma surface processing. Due to plasma formation on the Al surface, the effect of excimer laser irradiation under nitrogen atmosphere allows nitrogen diffusion and then AlN growth in the Al matrix. In this way, it is possible to avoid the adhesion problems encountered in film deposition processes. To understand the mechanisms governing this surface transformation, chemical and microstructural investigations were correlated with processing conditions. The influence of laser spots in overlapping mode from a step-by-step to quasi-continuous scan in the two in-plane directions, X and Y, were studied by grazing incidence X-ray diffraction and scanning electron microscopy, coupled with energy dispersive X-ray spectrometry analysis. These investigations were consequently correlated with wear resistance estimated by a pin-on-disc machine. The results show a strong enhancement of wear resistance when the overlapping rate is maximum in both the X and Y directions.

Fluence and mutagenic side effects of excimer laser radiation applied in ophthalmology in human lymphocytes in vitro

To investigate the influence of different fluences in 193 and 248 nm excimer laser radiation on the yields of chromatid and chromosome aberrations induced in human lymphocytes in vitro. Heparinized human blood was exposed to 193 or 248 nm excimer laser radiation. The fluence was gradually increased from 21 to 400 mJ/cm2 in 193 nm (constant total energy of 250 J) and from 150 to 377 mJ/cm2 in 248 nm radiation (constant total energy of 500 J). Chromatid and chromosome aberrations were then analysed microscopically. The yields of chromatid breaks and achromatic lesions depend on the fluence per pulse. This dependence contains a linear component, indicating a threshold of about 70 mJ/cm2 fluence in 193 nm and of about 250 mJ/cm2 fluence in 248 nm laser radiation. An increase of the yield of dicentric chromosomes could only be observed at the highest fluence tested (377 mJ/cm2) in the 248 nm series. Over 126 mJ/cm2 in 193 nm radiation no lymphocytes could be cultured and therefore no aberrations could be found. Our findings show that the fluence of 193 nm and of 248 nm excimer laser radiation has an effect on the yields of chromatid breaks and achromatic lesions in human lymphocytes under in vitro conditions.

Physico-chemical characterization of the effect of excimer laser irradiation on PMMA thin films

We study the cross-linking process taking place in poly(methylmethacrylate) upon irradiation at 248 nm with an excimer laser. The physical and chemical properties of the irradiated polymer are traced with FTIR spectroscopy, UV–visible spectrophotometry, and differential scanning calorimetry. In particular, the evolution of the glass transition temperature is examined as a function of the total energy deposited on the polymer surface. It appears that there occurs a competition between a cross-linking reaction and a photodegradation reaction.

ArF excimer laser irradiation of human dentin.

The use of excimer lasers for treatment of dental hard tissues has considerable potential because the combined characteristics of low wavelength and short pulse result in limited heat diffusion and, therefore, tissue ablation without the problems of collateral damage. To date, there are relatively few published studies concerning the effects of excimer laser irradiation on dental hard tissues. Thus the present study was conducted to examine the morphological changes in tooth dentin subsequent to ArF excimer laser irradiation. The morphologic changes induced in normal, nondiseased human dentin following irradiation by an ArF excimer laser at fluences ranging from 1 to 4 J/cm2 and the number of laser pulses ranging from 50 to 1,000 were evaluated by scanning electron microscopy. Two modes of ablation, photochemical at low fluences and thermal at high fluences, were observed. A fluence of 1 J/ cm2 when combined with 50 or 100 pulses produced a uniform ablation of the dentin surface without signs of tissue melting. At fluences > 1.5 J/cm2, the thermal mode of ablation was more efficient at removing intertubular dentin than peritubular dentin. Further, when compared to the lower fluences, the higher settings produced a rougher ablation crater surface. Additionally, the higher fluences produced surface melting with each pulse and sealing of exposed dentinal tubules after irradiation with 100-300 laser pulses. The photochemical and thermal mechanisms of tooth dentin ablation were identified based on significant differences in tissue morphology following laser irradiation. The rates of tissue ablation and the observed morphologic changes indicate that the ArF excimer laser could be useful for caries removal and sealing of exposed dentinal tubules.

Mössbauer Spectroscopy Evidence for Phase Selectivity in Excimer Laser Induced Amorphization of Thermally Annealed FeCoBSi Metallic Glass

Abstract Pulsed excimer laser irradiation effects (λ = 308 nm, τ = 10 ns, w = 3 J/cm2 , N = 2 laser pulses/spot, repetition rate 1 Hz) on the magnetic properties and phase composition of thermally annealed Fe66Co18B15Si1 metallic glass have been studied by transmission and conversion electron Möss-bauer spectroscopy (CEMS). Radiation-driven surface modifications were examined by scanning electron microscopy (SEM). Excimer laser induced amorphization was observed in partially crystallized Fe66Co18B15Si1 samples (T A = 648 K, t A = 1 hour) and was found to be accompanied by the development of laser-induced magnetic anisotropy. In totally crystallized Fe66Co18B15Si1 specimens (T A = 723 K, = 1 hour), the effect of excimer laser induced amorphization exhibited phase selectivity with respect to the crystalline components of the alloy system. When compared to bulk data, a different behavior of the surface magnetic texture and relative abundance of alloy phases was observed. The laser-induced phase transformation of thermally annealed Fe66Co18B15Si1 specimens was shown to consist of partial amorphization and surface oxidation of the irradiated material.