Excimer laser sources

There have been several experimental developments in the last few years that have resulted in more definitive experiments on photodissociation dynamics. First and foremost is the greater availability of intense laser sources, particular in the region below 300 nm (8,9). Excimer laser sources provide large numbers of photons at 157, 193, 222, 249, and 308... 

Previous workers had used the molecular beam TOF technique (134) and the VUV flash photolysis LIF technique (135). Ling and Wilson (136) had suggested that either the A(2n) state of CN is produced in the original photolysis process or that I atoms were produced in the Pi/2 and 3/2 states. It had been previously shown (135), by collisional quenching studies, that the A state of CN was not produced. This earlier work has been reviewed by Baronvaski (137) but recently both he and others have done further work on this molecule using excimer laser sources in both static gases and pulsed molecular beams. 

The number of resolution elements per unit area is expanded enormously by the scanning system. Such systems will easily provide the number of resolution elements required for 0.5-p.m ground rules. If such systems can be developed by using DUV excimer laser sources with a moderate NA,... 

Biomimetic nanocrystalline apatite coatings were deposited on titanium substrates by matrix-assisted pulsed laser evaporation (MAPLE), a technique with potential application in tissue engineering (Visan et al., 2014 Caricato etal., 2014). The targets were prepared from nano-sized, poorly crystalline apatite powders, analogous in composition to mineral bone. For the deposition of thin films, a KrF excimer laser source was used (A = 248 nm,rFWHM < 25 ns). Analyses of the deposited films showed that the structural and chemical nature of the nanocrystalline precursor apatite was preserved. Hence, MAPLE may be a suitable technique for the congruent transfer of a delicate material such as nanohydroxyapatite. 

Table 13.1 Commercially available excipiex and excimer laser sources. (Adapted from K. Jain. °) ...

Sandstrom, Argon fluoride excimer laser source for sub 0.25 [xm optical lithography, Proc. SPIE 1463, 610 616 (1991). 

To acconunodate the needs of photolithography, some polymers were developed that cross-link upon irradiation with an Ar-F excimer laser source at 193 nm [180]. To this end were synthesized cycloolefin-maleic anhydride-alternating copolymers. This material was formed by free-radical copolymerization of norbomene and maleic anhydride ... 

Deep UV systems (e.g., excimer laser sources at 248 nm wavelength)... 

Fig. 40. Schematic of an euv exposure tool. Key features are the excimer laser-driven x-ray source and the redective optical elements (including the mask) in...

To evaporate the source material, various heating methods are used such as resistance heating, electron beam, pulsed excimer laser, or cathodic arc (where the source is the cathode). 

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... 

For EPy-doped PMMA film, a 308 nm excimer laser (Lumonics TE 430T-2, 6ns) was used as as exposure source. We used a tine-correlated single photon counting systen (18) for measuring fluorescence spectra and rise as well as decay curves of a snail ablated area. The excitation was a frequency-doubled laser pulse (295 nm, lOps) generated from a synchronously punped cavity-dumped dye laser (Spectra Physics 375B) and a CW mode-locked YAG laser (Spectra Physics 3000). Decay curves under a fluorescence microscope were measured by the same systen as used before (19). 

Excimer lasers are of great importance for UV and vacuum UV (VUV) spectroscopy and photochemistry. They are also found in a wide range of applications. For example, they are used in micromachine medical devices, including refractive surgery, in photo-lithography for the microelectronics industry, for material processing, as optical pump sources for other type of lasers (dyes), and so on. More details about excimer lasers can be found in Rodhes (1979). 

Dubroeucz, G. M. Zahorsky, D. "KrF Excimer Laser as a Future Deep UV Source for Projection Printing," International Conference on Microlithography, Grenoble, France, Oct. 1982. 

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