Atomically clean crystalline surfac

B. Atom-Multiphonon Scattering Time-of-Flight Scattering Instrument Clean Crystalline Surfaces Ionic Insulators A. Alkali Halides... 

In most materials, however, the modification of the forces at the surface is such that the surface localized modes have frequencies which lie below the frequencies of an associated bulk band with the same symmetry they have the appearance of having been peeled down from this bulk band [24]. In the usual case, the lowest energy of all these peeled -down modes derives from the bulk transverse acoustic band and is normally sagittally polarized. This dispersion branch is called the Rayleigh wave (RW) because it was predicted by Lord Rayleigh from continuum wave theory over a century ago [38]. Helium atom scattering experiments on virtually every material so far investigated have detected the RW on clean crystalline surfaces. 

The data compiled in this chapter referto so-called "clean surfaces", i. e. crystalline surfaces that are atomically clean and well characterized. Data on interfaces are dealt with only marginally, in connection with MOS devices. 

Part 5 covers special structures such as liquid crystals, solid surfaces and mesoscopic and nanostructured materials. The chapter on liquid crystals covers physical properties of the most common liquid crystalline substances as well as some liquid crystalline mixtures. Data compiled in the chapter on solid surfaces refer to atomically clean and well characterized surfaces. The values reported are mainly averages from different authors where reference to the original papers is made. In the chapter on nanostructured materials emphasis is placed on size and confinement effects. The properties associated with electronic confinement are addressed and particular attention is drawn to semiconductor-doped matrices. The two main applications of nanostructured magnetic materials, spintronics and ultrahigh-density data storage media, are also treated. 

In addition to zeolites and MMS which are crystalline, ordered nanoporous materials and amorphous adsorbents, such as silica and active carbon, have been used in gas cleaning. The silica gel surface is generally terminated with OH groups bonded with a silicon atom, SiOH units, that is, silanols (see Figure 2.30). The concentration of OH groups at the surface is... 

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