Microelectronics, surface structure

Since most of the papers in this symposium deal primarily with the role of surface composition in industrial applications, in this section we depart from that path to consider an example of the role of surface structure in the performance microelectronics devices. 

Vitreous silica is important not only in the traditional ceramic and glass uses but also in its application in optical fibers, microelectronics, and catalysis. A detailed understanding of the bulk and the surface structure of the material is needed to improve optical fiber coatings, microelectronic devices, and catalytic supports. 

Of these, the most extensive use is to identify adsorbed molecules and molecular intermediates on metal single-crystal surfaces. On these well-defined surfaces, a wealth of information can be gained about adlayers, including the nature of the surface chemical bond, molecular structural determination and geometrical orientation, evidence for surface-site specificity, and lateral (adsorbate-adsorbate) interactions. Adsorption and reaction processes in model studies relevant to heterogeneous catalysis, materials science, electrochemistry, and microelectronics device failure and fabrication have been studied by this technique. 

In nanotechnology, dimensions of interest are shrinking from the fiva to the nm range. For many microelectronic devices, such as laterally structured surfaces, particles, sensors, their physical as well as their chemical properties are decisively determined by their chemical composition. Its knowledge is mandatory for understanding their behavior, as well as for their successful and reliable technical application. This presents a challenge for TOF-SIMS, because of its demand for the unique combination of spatial resolution and sensitivity. 

Thin films of metals, alloys and compounds of a few micrometres thickness, which play an important part in microelectronics, can be prepared by the condensation of atomic species on an inert substrate from a gaseous phase. The source of the atoms is, in the simplest circumstances, a sample of the collision-free evaporated beam originating from an elementary substance, or a number of elementary substances, which is formed in vacuum. The condensing surface is selected and held at a pre-determined temperature, so as to affect the crystallographic form of the condensate. If this surface is at room temperature, a polycrystalline film is usually formed. As the temperature of the surface is increased the deposit crystal size increases, and can be made practically monocrystalline at elevated temperatures. The degree of crystallinity which has been achieved can be determined by electron diffraction, while other properties such as surface morphology and dislocation structure can be established by electron microscopy. 

The differently produced conductive polymer structures described above all have enhanced conductivity, which can be employed in microelectronics [44] and as sensors using immobilized enzymes [46, 47[. Martin and coworkers used polarized infrared absorption spectroscopy to access the alignment of the polymer fibers on the outer surface of the nanotubes [48[. The study showed that the enhancement of the conductivity is due to the alignment of the polymer fibers on the outer surface of the tubes. 

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