XeCl-Excimer laser

The potential of LA-based techniques for depth profiling of coated and multilayer samples have been exemplified in recent publications. The depth profiling of the zinc-coated steels by LIBS has been demonstrated [4.242]. An XeCl excimer laser with 28 ns pulse duration and variable pulse energy was used for ablation. The emission of the laser plume was monitored by use of a Czerny-Turner grating spectrometer with a CCD two-dimensional detector. The dependence of the intensities of the Zn and Fe lines on the number of laser shots applied to the same spot was measured and the depth profile of Zn coating was constructed by using the estimated ablation rate per laser shot. To obtain the true Zn-Fe profile the measured intensities of both analytes were normalized to the sum of the line intensities. The LIBS profile thus obtained correlated very well with the GD-OES profile of the same sample. Both profiles are shown in Fig. 4.40. The ablation rate of approximately 8 nm shot ... 

Uchino, O., Mizunami, T., Maida, M., and Miyazoe, Y. (1979) Efficient dye lasers pumped by an XeCl excimer laser. Appl. Phys. 19, 35. 

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... 

Sameshima, T. Usui, S. Sekiya, M. 1986. XeCl excimer laser annealing used in the fabrication of poly-Si TFTs. IEEE Electron Device Lett. 7 276-278. 

Two-photon absorption chemistry of 2AP, specifically photoionization processes, can be induced by intense nanosecond 308-nm XeCl excimer laser pulses [10]. Typical transient absorption spectra of 2AP in deoxygenated neutral aqueous solutions are shown in Fig. 1. The stronger (385 nm) and weaker (510 nm) absorption bands were assigned to 2AP radicals derived from the ionization of 2AP (bleaching near 310 nm) [10], whereas a structureless absorption band from -500 to 750 nm corresponds to the well-known spectrum of the hydrated electron (eh ) [41]. 

Fig. 1a,b Transient absorption spectra of 2AP (0.1 mM) in deoxygenated 20 mM phosphate buffer (pH 7) solutions recorded after 308-nm XeCl excimer laser pulse excitation (70 mj pulse" cm" ) [10]. The decay of hydrated electrons was recorded at 650 nm (a) and bleaching of the 2AP band at 310 nm (b). Reprinted with permission from the J Phys Chem, Copyright (1999) American Chemical Society... 

We have investigated the reactions of the COs " radicals with double-stranded DNA by laser flash photolysis techniques [15]. In these time-re-solved experiments, the COs radicals were generated by one-electron oxidation of HCOs by sulfate radical anions, SO4 the latter were derived from the photodissociation of persulfate anions, S20s initiated by 308-nm XeCl excimer laser pulse excitation. In air-equilibrated buffer solution containing the self-complementary oligonucleotide duplex d(AACGCGAATTCGCGTT), 208 , and an excess of HCO3., the decay of the CO3 radical anion absorption band at 600 nm is associated with the concomitant formation of the characteristic narrow absorption band of the G(-H) radicals near 310 nm. 

Cu+ emission spectra were recorded using a nanosecond laser kinetic spectrometer (Applied Photophysics). Cu+-zeolites were excited by the laser beam of the XeCl excimer laser (Lambda Physik 205, emission wavelength 308 nm, pulse width 28 ns, pulse energy 100 mJ). The 320-nm filter was situated between 2 mm thick silica cell and monochromator. Emission signal was detected with the photomultiplier R 928 (Hamamatsu), recorded with the PM 3325 oscilloscope and processed by a computer. All the luminescence measurements were carried out at room temperature. The Cu+ emission spectra were constructed from the values of luminescence intensity at the individual wavelengths of emission in selected times after excitation (2, 5,10, 20, 50, 100 and 200 ps). For details see Ref [7]. 

The lignin model compounds and their derivatives used in this study were custom synthesized at Queen s University by Dr. R. Bowers (Colour Your Enzyme). CIDEP and conventional ESR experiments were conducted using either a Varian E-104 spectrometer or a customized Bruker X-band spectrometer, modified similarly as previously described (7). The light source used for in situ irradiation was either a super high pressure 200 W mercury lamp, a Lambda-Physik EMG101-MSC XeCl excimer laser at 308 nm., or a Quanta-Ray GCR-11 Nd YAG solid state laser equipped for all four harmonic generations. 

A XeCl excimer laser (308 nm) was used to photoablate biodegradable polymers (PDLA and PVA) into channels (10-50 pm deep) [196],... 

Our laser system consists of three stages A XeCl excimer laser, a combination of dye and Ti Sa laser, and a H2 Raman cell for conversion to 6 pm (Fig. 8). 

Fig. 8. The components of the laser system. The high power XeCl excimer laser pulse triggered my the muon entrance detector is converted in two steps to a high quality 7 ns long pulse of 708 nm which is shifted to the desired 6 pm light inside the multipass Raman cell. The light is injected into a multipass cavity to effectively illuminate the muon stop volume inside the PSC solenoid. High resolution frequency selection is provided by injection of a cw Ti Sa laser...

Bigger clusters have been formed, for instance, by the expansion of laser evaporated material in a gas still under vacuum. For metal-carbon cluster systems (including M C + of Ti, Zr and V), their formation and the origin of delayed atomic ions were studied in a laser vaporization source coupled to a time-of-flight mass spectrometer. The mass spectrum of metal-carbon cluster ions (TiC2 and Zr C j+ cluster ions) obtained by using a titanium-zirconium (50 50) mixed alloy rod produced in a laser vaporization source (Nd YAG, X = 532 nm) and subsequently ionized by a XeCl excimer laser (308 nm) is shown in Figure 9.61. For cluster formation, methane ( 15% seeded in helium) is pulsed over the rod and the produced clusters are supersonically expanded in the vacuum. The mass spectrum shows the production of many zirconium-carbon clusters. Under these conditions only the titanium monomer, titanium dioxide and titanium dicarbide ions are formed. 

Tin dioxide thin films can be grown on silicon at room temperature by XeCl excimer laser metal-organic deposition (MOD 100 mJ cm, repetition rate 10 Hz for 5 min) from a solution of Sn(acac)2 in w-BuOH, whereby crystalline films were obtained without heat treatment . Increasing the laser energy to 260 mlcm resulted in an improvement of the crystallinity, which is even better than that of films prepared at 900 °C without laser irradiation. Molloy and coworkers used bimetallic [Sn(dmae)2Cd(acac)2]2 (dmae = dimethylaminoethanol) as precursor for AA-CVD of amorphous Sn02 films, containing no detectable amounts of cadmium. 

Similarly, intensity measurements utilizing a pulsed XeCl excimer laser (308 nm, 15 ns, and 150 mJ/pulse) have been carried out using a dye laser unit as flow-through cell for a lO M azobenzene solution (18). A linear correlation was found between the increase in absorbance at 358nm and the number of laser pulses (Ap), and the energy (E ) per laser pulse can be calculated using Eq. (21), i.e.. 

In summary, concentrated azobenzene solutions represent reliable chemical actinometers for pulsed UV sources, such as the nitrogen laser line at 337.1 nm, the third harmonic output of Nd YAG lasers at 355 nm, or the XeCl excimer laser line at 308 nm. In contrast to the ferrioxalate actinometers, the azobenzene actinometers are not restricted to low-energy lasers but can measure laser pulse energies up to 150 mJ. 

In a similar way, anthracene triplet (4>,gj3=0.71, z =6A,700Mr cmr ) and the naphthalene triplet (4>jg = 0.75, e j = 24,500 M" cm" ) in cyclohexane solution have been introduced as transient chemical actinometers for the third-harmonic (355 run) and fourth-harmonic (266 nm) output of Nd YAG lasers, respectively (44). In summary, transient chemical actinometers are ideal for accurately measuring the energy of single laser pulses, provided the quantum yields and extinction coefficients of the transients are well known (45 7). Thus, the well-established benzophenone actinometer (42-44) has been used as a reliable reference to calibrate the azobenzene actinometer (see section "Laser Intensity Measurements with the Azobenzene Actinometer" Doherty S, Hubig SM, unpublished results) and the Aberchrome 540 actinometer (48,49) for intensity measurements with pulsed Nd YAG and/or XeCl excimer lasers. However, such actinometer can only be used when a complete set of laser flash photolysis equipment including a kinetic spectrometer is available. 

Lin (83) studied the MRS resist (RD2000N) to determine the effect of optical density on performance. Resist images were delineated by 222-nm KrCl and 308-nm XeCl excimer laser radiation as shown in Figure 3.72. At 308 nm, nearly vertical resist profiles were produced. This result provides... 

In Ref. [185], a Cu surface was abraded with diamond powder, and the diamond deposition was done by HFCVD under conditions of c 1 %CH4/H2, P = 20Torr, and rs = 800°C for 2h. As a result, a diamond film, consisting of diamond grains of 0.5 pm in diameter, was deposited. A patterning by selective deposition was found to be possible by irradiating KrF or XeCl excimer laser pulses on unnecessary areas. 

In a series of XeCl excimer laser photofragmentation and reaction tests with O2 and ammonia reactants, we were able to prove that all these clusters were, in fact, (Lax C,) lanthanum fuUerenes. As levitated positive ions in the FT-ICR apparatus, they are chemically inert, and they fragment only by successive C2 loss. Laser shrink wrapping experiments showed that the smallest cage that can surround two lanthanum atoms is and the minimum cage that can fit around three is Cgg. 

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