Irradiation pulsed laser

The enhancement of nucleation and adhesion of diamond films has been achieved on Cu, stainless steel and Si using a pulsed laser irradiation pretreatment, followed by HFCVD.t l A thin buffer layer of a-C, WC or cBN was first deposited on the substrates by pulsed laser evaporation, followed by pulsed laser irradiation. For the Cu substrates, diamond nucleation densities on the a-C overlayer and WC (or cBN) buffer layer were 

4-5 times and more than an order of magnitude, respectively, higher than that on an untreated Cu substrate. It is postulated that the irradiation converted some of the a-C on the surface into diamond or led to a reaction product that cilitates the nucleation of diamond. Laser can evaporate carbon preferentially, leaving diamond particles unaffected. In addition, the irradiation might melt the substrate sur ce and embed diamond particles into it, leading to an improvement in the adhesion of the diamond films with the substrates. 

The deposition of diamond on stainless steel substrates is quite difficult but technologically very important. The difficulty is due partly to the very high diffusion rate of C into steel, leaving insufficient C or DLC on the substrate surface for diamond nucleation. The laser irradiation pro-cessf297] jnay lead to the formation of carbide phases or diamond microcrystallites in the C overlayer on a stainless steel substrate, providing nuclei fpr diamond growth during subsequent HFCVD. The WC or cBN buffer layers on stainless steel substrates act as a diffusion barrier which makes the surfece rapidly achieve carbon saturation. 

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Photothermal sensitization has been mentioned briefly with regard to nickel(II) octabutoxy-naphthalocyanine (Section 9.22.10.1). A similar phenomenon has been observed with copper(II) haematoporphyrin ((1), Cu for 2H).196 This substance is accumulated by amelanotic melanoma cells. When the impregnated cells were subjected to light from a quartz-halogen lamp cell survival was not affected (i.e., no PDT effect), but intense pulsed laser irradiation (532 nm, Q-switched... 

D.M. Zehner, Surface Studies of Pulsed Laser Irradiated Semiconductors D.H. Lowndes, Pulsed Beam Processing of Gallium Arsenide R.B. James, Pulsed C02 Laser Annealing of Semiconductors R. T. Young and R.F. Wood, Applications of Pulsed Laser Processing... 

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 PLP-SEC method, like the rotating sector method, involves a non-steady-state photopolymerization [Beuermann, 2002 Beuermann and Buback, 2002 Komherr et al., 2003 Nikitin et al., 2002], Under pulsed laser irradiation, primary radicals are formed in very short times ( 10 ns pulse width) compared to the cycle time ( 1 s). The laser pulse width is also very short compared to both the lifetimes of propagating radicals and the times for conversion of primary radicals to propagating radicals. The PLP-SEC method for measuring kp requires that reaction conditions be chosen so that no significant chain transfer is present. The first laser pulse generates an almost instantaneous burst of primary radicals at high... 

Fig. 3.20 The peak temperature reached by pulsed laser irradiation of a tip as a function of the energy flux of the laser pulse for Rh, Pt and W tips. The pulse width is 300 ps. Data are also given for 5 ns pulse width for W.

Figure 4. Kinetics of the polymerization of polyester- and epoxy-acrylate photoresists under pulsed laser irradiation at 337.1 nm in the presence of air.

An important quantity that can be deduced from the reaction profile is the rate of the cross-linking polymerization (Rp), i.e., the number of double bonds polymerized or of cross-links formed per second. Rp values were determined from the maximum slope of the kinetic curves (usually reached for conversion degrees between 20 and 40%). Table I summarizes the Rp values for the two photoresists tested under various conditions, namely conventional UV and continuous or pulsed laser irradiation at different light intensities. According to these kinetic data, Rp increases almost as fast as the light-intensity the ratio Io/Rp which is directly related to the product of the light-intensity and the required exposure time was found to vary only in the range 10-8 to... 

Effect of separation space on yield was found in some experiments. A higher quantum yield was observed for In2S3 with larger particle size when the electron transfer to methylviologen in aqueous solution was examined by pulse-laser irradiation.13) A decrease in the yield of the products with decreasing size has also been reported for the photocatalytic polymerization of methyl methacrylate with ZnO of the size ranging from 4 to 40 nm 15) this was attributed to the increase in the recombination caused by the reduction of the dimensions. 

Abdallah Jr. J, Csanak G, Fukuda Y, Yamakawa K, Akahane Y, Aoyama M, Inoue N, Ueda H, Faenov AYa, Magunov AI, Pikuz TA, Skobelev IYu (2003) Time-dependent Boltzmann kinetic model of X-rays produced by ultrashort-pulse laser irradiation of argon clusters. Phys. Rev. A 68 0632011-0632018... 

D. H. Lawndes and G. E. Jettison, Jr., Time-Resolved Measurement During Pulsed Laser Irradiation of Silicon D. M. Zebner, Surface Studies of Pulsed Laser Irradiated Semiconductors... 

Laser ablation is one of the modem and frequently used methods. The disadvantage of broad size distribution could be improved by the so-called laser-induced size reduction . For instance, in the case of gold nanoparticles, their well expressed plasmon resonance around 520 nm can be used to influence the size and shape of the particles.Thus, more or less monodisperse gold particles of 1.7nm and 3.4nm could be generated with a 532-nm pulsed laser irradiation of gold metal plates in diluted sodium dodecylsulfate solutions. ... 

Pulsed laser irradiation of both the alcohol and the ketone gave strong transient absorption spectra. Both spectra resemble that of the Ceo triplet [99]. That of the alcohol (tj = 21 p) is shown in Fig. 3. 

Time evolution of the ground state hole as well as fluorescence spectra initiated by a short pulse laser irradiation in solution has been conventionally explained in terms of the two-dimensional configuration coordinate model by Kinoshita . According to his theory, two adiabatic potential curves corresponding to the ground and excited states are assumed to have the same curvature but have the different potential minimum in the configuration coordinate. 

The theory of thermal aspects of laser desorption has been developed for a substrate surface subjected to pulsed laser irradiation, assuming that the laser intensity has a Gaussian distribution [21], The given surface is covered with the organic layer, which does not absorb the laser energy. However, the heat flux in the substrate that absorbs the energy heats the sample to the same temperature as the substrate. For this case, the laser intensity flux /(r,t) is given by... 

Zhigilei, L.V. and Garrison, B.J. (1998) Computer simulation study of damage and ablation of submicron particles from short-pulse laser irradiation. Appl. Surf. Sci., 127-129, 142-150. 

Figure 34.13 Viabilities of HeLa cells following pulsed laser irradiation (1064 nm, 10 Hz, 250 mj pulse-1) without (a) and with (b, c) PC-NRs in the medium. PC-NR concentrations in the medium (a) 0, (b) 0.4, (c) 0.8 mM (Au atoms).

More recent experiments have addressed the photochemistry of Fe(CO)5 on the surface of single crystals under ultra-high vacuum conditions (10,33,34). It is difficult to compare our results with the results of these experiments, but some interesting results have been obtained. In the experiments by Friend and coworkers (10) for example, Fe(C0)s is adsorbed onto the surface of Si(lll) at low temperature, yielding roughly monolayer coverage. Photolysis is carried out by pulsed laser irradiation at an average fluence of... 

Fig. 10.13. Random and channeling backscattering spectra of as-implanted Si (100) showing the annealing results from pulsed laser irradiation (Q-switched ruby laser 1.6 J cnT2, 75As 100 keV, 1.4 x 10ls in (100) Si, [110] aligned spectrum) (after White et al. 1979)...

Pulsed laser irradiation of a thin buffer layer of a-C, WC or cBN deposited on Cu, stainless steel, and Si substrates leads to enhancement of nucleation and adhesion of diamond film.s on the substrates. The irradiation may convert a portion of the a-C on the surface into diamond or result in the formation of a reaction product that cilitates diamond nucleation. 

M. F. Modest and H. Abakians, Heat Conduction in a Moving Semi-Infinite Solid Subjected to Pulsed Laser Irradiation, J. Heal Transfer, 108, pp. 597-601,1986. 

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