UV-excimer laser irradiation

The work by Pireaux et al. (1995) on the so-called reactive (pol3detra-fluoroethylene) and even more stable (polypropylene and polyethylene) polymers based on the use of XPS valence band spectra, showed that irradiation can lead to superficial structural modification - lateral chain grafting, or cross-linking. This structural modification appears more pronounced for high fluence UV excimer laser irradiation in air, than for (more moderate) exposition to harder X-rays in vacuum. 

Compaction has also been observed as a result of neutron irradiation and extended exposure to iatense uv (excimer) laser light (131,132). The compaction tends to relax over months at room temperature and can be reversed quickly by annealing at sufficiently high temperatures (133). 

A photosensitive composition, consisting of an aromatic azide compound (4,4 -diazidodi-phenyl methane) and a resin matrix (poly (styrene-co-maleic acid half ester)), has been developed and evaluated as a negative deep UV resist for high resolution KrF excimer laser lithography. Solubility of this resist in aqueous alkaline developer decreases upon exposure to KrF excimer laser irradiation. The alkaline developer removes the unexposed areas of this resist. 

The UV spectra for this resist film, before and after exposure to KrF excimer laser irradiation for 100 mJ/cm2, are shown in Figure 6. The absorbance of the azide renders the reist film of l.o micron thickness essentially opaque at 248 nm. After exposure of 100 mJ/cm2, the absorbance bleaches from 0.5 to 6.0% at 248 nm. Intense absorption by this resist at 248 nm closely relates to the pattern profile of the resist, which will be discussed in the last section. 

Iwanaga S, Akiyama Y, Kikuchi A et al (2005) Fabrication of a cell array on ultrathin hydrophilic polymer gels utilising electron beam irradiation and UV excimer laser ablation. Biomaterials 26(26) 5395-5404... 

The transmission for ns UV pulses is clearly dependent on the fluence in a range of a few mj cm-2 to several J cm"2. With 248-nm irradiation, only a slight increase of the transmission ratio, TH/TL, could be detected, whereas with the XeCl excimer laser irradiation much higher transmission ratio values are reached which are close to the theoretical limit. 

Finally, we tried to activate dopant atoms using pulsed laser irradiation, which is effective in lowering the process temperature. The light source was a 308-nm XeCl excimer laser, which is a standard source for crystallizing a-Si films used in the LTPS process.19 A test sample of 76 nm thickness, prepared from the copolymerized solution (l-wt% phosphorus, 30-min UV irradiation, 500 °C 2hr annealing), was irradiated using a XeCl laser at various intensities to activate the dopant atoms. Figure 5.19 shows the relationship between the... 

The irradiation of a polymer surface with the high intensity, pulsed, fer-UV radiation of the excimer laser causes spontaneous vaporization of the excited volume. This phenomenon was first described by Srinivasan (1) and called ablative photodecomposition. The attention of many researchers was drawn to the exceptional capabilities of photoablation (2). Etching is confined to the irradiated volume, which can be microscopic or even of submicron dimensions, on heat-sensitive substrates like polymers. In most experimental conditions, there is no macroscopic evidence of thermal damage, even when small volumes are excited with pulses of... 

Both LDI and MALDI make use of the absorption of laser light by a solid sample layer. The energy uptake upon laser irradiation then causes evaporation and ionization of the sample. Wavelengths ranging from ultraviolet (UV) to infrared (IR) have been employed, e.g., nitrogen lasers (337 nm), excimer lasers (193, 248, 308 and 351 nm), Q-switched, frequency-tripled and quadrupled Nd Yag lasers (355 and 266 nm, respectively), [24] Er Yag lasers (2.94 pm) [24,25] and TEA-CO2 lasers (10.6 pm). [16,26]... 

After irradiation, a silver-colored thin polymer layer totally covers the liquid phase. During the irradiation process, the color of the liquid phase has changed from yellow to a deep red one. The red color is due to a charge transfer complex between iodine and the thiophene ring dissolved in the liquid. The polymerization process takes place only at the surface of the irradiated sample. However, it was observed that when the UV-irradiation by excimer laser is over, the polymerization process continues, but only at the surface of the irradiated sample a postpolymerization without incident UV-photons takes place. It was also observed that the presence of oxygen during... 

The main reactions taking place when chloromethylated polystyrene (CMS) and chloromethylated poly(diphenylsiloxane) (SNR) are irradiated with high energy electrons or deep UV (KrF excimer laser, 248 nm) radiation have been studied. The results are discussed in terms of short-lived reactive species generated using pulse radiolysis and laser (248 nm) photolysis techniques. 

Figure 1 shows the ultraviolet (UV) spectra of an unexposed MP2400-17 film and a film exposed to 470 mJ/cm. The films were spin coated onto quartz substrates and baked at 90 C for 30 minutes in a forced-air oven. The film thickness after baking was 0.465 bm. Exposure was accomplished by direct irradiation of the film to the narrowed output of a Math Sciences EXL-100 KrF excimer laser. Thirty pulses were delivered at an average dose of 15.7 mj/cm per pulse. The spectrum of the quartz substrate was automatically subtracted from the spectra of the films on the substrates to obtain Figure 1. The absorbance of the two films is the same at wavelengths below 310 nm and the solid curve in Figure 1 represents the absorbance of both films. The absorbance at 248 nm is 0.49 for both films. Destruction of the PAG by the 248 nm radiation, as evidenced by the disappearance of the longer wavelength absorption in the irradiated film, presumably occurs after nonradiative energy transfer.

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