Laser sputtering

Our approach is similar to that employed in research of free cluster ions in the gas phase, where various measurements are conducted on the cluster which is mass selected out of the size-distributed clusters generated by laser sputtering. Based on the chemical compositions of the isolated MFCs, we discuss the determining factors of core size in connection with the formation processes. Some core-size dependent properties of the MFCs are also presented. 

Unfortunately, some of the analyzed molecules, as most biologically related molecules (e.g., amino acids), are solids with extremely low vapor pressures at room temperature and rapidly decompose when they are heated. For these molecules, which cannot be thermally vaporized, laser ablation or desorption have been alternatively used to produce neutral species in the gas phase.Both methodologies refer to laser-induced particle removal (laser sputtering) from a surface under the two extremes of massive and negligible rates of surface erosion, respectively. 

Laser-induced multiphoton excitation, 160 Laser sputtering, 158 Li -bound diol complexes, 204 LIF spectroscopy... 

L.B. Knight et al., Laser sputtering generation of B2 for ESR matrix isolation studies Comparison with ab initio Cl theoretical calculations. J. Am. Chem. Soc. 109, 3521-3525 (1987)... 

R. Kelly, A. Miotello, Mechanisms of Pulsed Laser Sputtering. In Pulsed Laser Deposition of Thin Films, ed. by D.B. Chrisey, G.H. Hubler (Wiley, New York Chichester Brisbane Toronto Singapore 1994) pp 55-88... 

Various aerosol processes have been developed for the generation of ultrafine powders at laboratory s e, such as flame (2), tube furnace (5), gas-condensation (4), thermal plasma (5), laser, sputtering and a variety of other aerosol processes named after the energy sources which are applied to provide the high temperatures during gas-to-particle conversion. However, until now, only flame processes have been scaled up to produce commercial quantities of ceramic particulates, such as silica, titania, etc., at low cost (about 1/lb). 

The fonnation of clusters in the gas phase involves condensation of the vapour of the constituents, with the exception of the electrospray source [6], where ion-solvent clusters are produced directly from a liquid solution. For rare gas or molecular clusters, supersonic beams are used to initiate cluster fonnation. For nonvolatile materials, the vapours can be produced in one of several ways including laser vaporization, thennal evaporation and sputtering. 

The requirements of thin-film ferroelectrics are stoichiometry, phase formation, crystallization, and microstmctural development for the various device appHcations. As of this writing multimagnetron sputtering (MMS) (56), multiion beam-reactive sputter (MIBERS) deposition (57), uv-excimer laser ablation (58), and electron cyclotron resonance (ECR) plasma-assisted growth (59) are the latest ferroelectric thin-film growth processes to satisfy the requirements. 

A high temperature optical fiber thermometer has beea developed (32,33). It coasists of a sputtered iridium blackbody tip oa a single crystal sapphire laser. Such a device has beea showa to be accurate to within 0.03° C at 1000°C. 

Alternative Thin-Film Fabrication Approaches. Thin films of electronic ceramic materials have also been prepared by sputtering, electron beam evaporation, laser ablation, chemical beam deposition, and chemical vapor deposition (CVD). In the sputtering process, targets may be metal... 

In Surface Analysis by Laser Ionization (SAU) ionized and neutral atoms are sputtered from the sample surface, typically using an ion beam (like SIMS) or a... 

In other articles in this section, a method of analysis is described called Secondary Ion Mass Spectrometry (SIMS), in which material is sputtered from a surface using an ion beam and the minor components that are ejected as positive or negative ions are analyzed by a mass spectrometer. Over the past few years, methods that post-ion-ize the major neutral components ejected from surfaces under ion-beam or laser bombardment have been introduced because of the improved quantitative aspects obtainable by analyzing the major ejected channel. These techniques include SALI, Sputter-Initiated Resonance Ionization Spectroscopy (SIRIS), and Sputtered Neutral Mass Spectrometry (SNMS) or electron-gas post-ionization. Post-ionization techniques for surface analysis have received widespread interest because of their increased sensitivity, compared to more traditional surface analysis techniques, such as X-Ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES), and their more reliable quantitation, compared to SIMS. 

Figures Quantitative high depth resoiution profile of a complex Ai Ga. j As laser diode test structure obtained using electron-gas SNMS in the direct bombardment mode, with 600-V sputtering energy. The data have been corrected for relative ion yield variations and summed to Al + Ga = 50%. The 100-A thick GaAs layer is very well resolved.

SNMS sensitivity depends on the efficiency of the ionization process. SNs are post-ionized (to SN" ) either hy electron impact (El) with electrons from a hroad electron (e-)heam or a high-frequency (HF-) plasma (i.e. an e-gas), or, most efficiently, hy photons from a laser. In particular, the photoionization process enables adjustment of the fragmentation rate of sputtered molecules by varying the laser intensity, pulse width, and/or wavelength. 

A versatile Laser-SNMS instrument consists of a versatile microfocus ion gun, a sputtering ion gun, a liquid metal ion gun, a pulsed flood electron gun, a resonant laser system consisting of a pulsed Nd YAG laser pumping two dye lasers, a non-resonant laser system consisting of a high-power excimer or Nd YAG laser, a computer-controlled high-resolution sample manipulator on which samples can be cooled or heated, a video and electron imaging system, a vacuum lock for sample introduction, and a TOF mass spectrometer. 

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