Post beams

Parallel strand lumber (PSL) Strands from softwood veneer PF s Headers, beams, columns and posts industrial uses such as bridge structures and power poles and with CCA pressure treatment, post, beams and columns for decks, balconies, car-ports 280 by 430 cross section (11 by 17), length up to 66 ft ... 

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. 

The basic principle of e-beam SNMS as introduced by Lipinsky et al. in 1985 [3.60] is simple (Fig. 3.30) - as in SIMS, the sample is sputtered with a focused keV ion beam. SN post-ionization is accomplished by use of an e-beam accelerated between a filament and an anode. The applied electron energy Fe a 50 20 eV is higher than the range of first ionization potentials (IP) of the elements (4—24 eV, see Fig. 3.31). Typical probabilities of ionization are in the 0.01% range. SD and residual gas suppression is achieved with electrostatic lenses before SN post-ionization and energy filtering, respectively. 

Surface analysis by non-resonant (NR-) laser-SNMS [3.102-3.106] has been used to improve ionization efficiency while retaining the advantages of probing the neutral component. In NR-laser-SNMS, an intense laser beam is used to ionize, non-selec-tively, all atoms and molecules within the volume intersected by the laser beam (Eig. 3.40b). With sufficient laser power density it is possible to saturate the ionization process. Eor NR-laser-SNMS adequate power densities are typically achieved in a small volume only at the focus of the laser beam. This limits sensitivity and leads to problems with quantification, because of the differences between the effective ionization volumes of different elements. The non-resonant post-ionization technique provides rapid, multi-element, and molecular survey measurements with significantly improved ionization efficiency over SIMS, although it still suffers from isoba-ric interferences. 

Figure 6.4 Atypical multi-bay beam and post construction...

When FAB is utilized for FC-MS, often known as continuous-flow FAB, a matrix material is added to the HPFC eluent, either pre- or post-column, and this mixture continuously flows to the tip of a probe inserted into the source of the mass spectrometer where it is bombarded by the atom beam (Figure 3.3). 

Electron Beam Lithography. LB PMMA films with thicknesses of 6.3 nm (7 layers) are sufficient for patterning a Cr film suitable for photomask fabrication. For ultrathin PMMA films the resolution (see Fig. 1) is limited by the smallest spot diameter available on MEBES I (1/8 pm). However, it is not possible to obtain this resolution if a thicker resist (>100 nm) is used under the same exposure and development conditions, which demonstrates that ultrathin resists are able to minimize the proximity effect. Also, since the radius of gyration of 188,100 Mw PMMA is about 10 nm in the bulk, and the thickness of the 7 layer film (6.3 nm) is less than 10 nm, it is reasonable to assume there must be an alteration of chain configuration in the ultrathin films. This will be particularly true when the post-deposition baking temperature of the multilayer films is less than the glass transition temperature (115°C), as is the case for the present experiments. In such a case, interdiffusion of PMMA chains between the deposited layers may not result in chain configurations characteristic of the bulk. 

Methods 1 and 3 have been utilized in dry developed resist systems. To our knowledge, there are no resist systems commercially available that depend on post-exposure treatment other than the post-curing effect in negative electron beam resists mentioned earlier. Since such systems are still largely in the research phase we will not discuss them here but rather refer the reader to the literature for more detailed descriptions (44-50). 

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