Laser, ablation wavelength

Figure Bl.22.7. Left resonant seeond-hannonie generation (SHG) speetnimfrom rhodamine 6G. The inset displays the resonant eleetronie transition indueed by tire two-photon absorption proeess at a wavelength of approximately 350 mn. Right spatially resolved image of a laser-ablated hole in a rhodamine 6G dye monolayer on fiised quartz, mapped by reeording the SHG signal as a fiinetion of position in the film [55], SHG ean be used not only for the eharaeterization of eleetronie transitions within a given substanee, but also as a mieroseopy tool.

Approximately 70 different elements are routinely determined using ICP-OES. Detection limits are typically in the sub-part-per-billion (sub-ppb) to 0.1 part-per-million (ppm) range. ICP-OES is most commonly used for bulk analysis of liquid samples or solids dissolved in liquids. Special sample introduction techniques, such as spark discharge or laser ablation, allow the analysis of surfaces or thin films. Each element emits a characteristic spectrum in the ultraviolet and visible region. The light intensity at one of the characteristic wavelengths is proportional to the concentration of that element in the sample. 

A LSX-200 Plus Laser Ablation System (CETAC Technologies, Omaha, Nebraska, USA), using a Nd YAG laser with a wavelength of 266 nm, was used for the analyses. A spot size of 100 pm was selected. Sufficient volume of ablated... 

Laser Ablation. A mixture of UFPs composed of TiN and Ti was synthesized by laser ablation of titanium in N2 gas at 0.1 MPa using an Nd YAG laser (wavelength 1.06 xm) with peak power of 10 kW for 200-ns pulse (33). This method, however, was not successful in obtaining nitride UFPs of Mo, Al, Fe, and Si. Pure TiN UFPs were produced using a high-power YAG laser generator maximum power of 80 J/pulse, repetition rate of 4-10 pulses/s (34). The particle size of TiN UFPs obtained was about 20 nnr at an ambient N2 gas pressure of 13.3 kPa, and decreased with decreasing N2 gas pressure. AIN UFPs can be synthesized by an excimer laser (12 J/cm2) ablation of aluminum under N2 gas pressure of 10 kPa and the subsequent calcination at 900°C for 2 hr under N2 flow (35). 

Although Eq. (2) is not adequate to fully describe ablation processes, the absorption coefficient is still a useful parameter as it provides a quantitative evaluation of the level of interaction between a given medium and photons of a specific wavelength and, to a first-order approximation, their propensity to laser ablation. 5 different materials can have different chemical compositions and structural arrangements, it is not surprising that they have different absorption coefficients and thus can exhibit different ablation characteristics. This is indeed found to be the case. For instance, PMMA is readily structured at 193 run ( 193 2 X 10 cm I) although it is essentially transparent and unaffected at 308 nm (a 308 < 1 x 10 cm i). However, for an aromatic polyimide such as the system whose dianhydride/diamine components are pyromelletic dianhy-dride/oxydianiline (PMDA-ODA), ablation occurs readily not only at 193 nm... 

Figure 21-26 Emission from a plasma produced by laser irradiation of the high-temperature superconductor YBCI2CU3O7. Solid is vaporized by the laser and excited atoms and molecules such as YO emit light at characteristic wavelengths. [From w.a. warmer. "Plasma Emission from Laser Ablation of YBa2Cuj07." Appf. Phys. Lett. 1988, 52.2171]...

To analyze metals and alloys directly without dissolution, both spark ablation [349] and laser ablation [61,211] dry aerosol generation systems have been used to introduce samples into an ICP-MS. These approaches often require matrix-matched standards, although several active research groups are focusing on techniques to reduce that requirement. The amount of material ablated depends on the sample type. Fractionation of elements can also be a problem, depending on the sample, the laser fluence, the laser wavelength, and the number of laser pulses used to sample from a fixed location. Volatile elements that are segregated in the samples appear to be most prone to fractionation problems [61],... 

Figure 5.22 Schematic of laser ablation inductively coupled plasma mass spectrometer a laser ablation system (wavelength 213 nm) is coupled to a double-focusing sector field ICP-MS (Element, Thermo Fisher Scientific, Bremen). The cooled laser ablation chamber using two Peltier elements was developed in the author s laboratory. (M. V. Zoriy, M. Kayser, Izmer, C. Pickhardt and ). S. Becker, Int J. Mass Spectrom., 242, 297 (2005). Reproduced by permission of Elsevier.)...

The application of LA-ICP-ToF-MS and LA-ICP-QMS for depth profiling of various titanium based coatings on steel and tungsten carbide and Ti based single layers is discussed in references respectively. Thickness determination was performed by LA-ICP-QMS with 5% RSD, a laser ablation rate of < 100 nm per laser shot (Nd-YAG laser at wavelength 266 nm using a laser energy of 1.5 ml at 120 p,m laser spot size), and a depth resolution of 2.5 p-m was observed. ... 

Smejkal P, Siskova K, Vlckova B, Pfleger J, Sloufova I, Slouf M, Mojzes P (2003) Characterization and surface-enhanced Raman spectral probing of silver hydrosols prepared by two-wavelength laser ablation and fragmentation. Spectrochim Acta A 59 2321-2329... 

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