Single-crystal Substrate

Other interesting thin-film studies using AES have included the growth of platinum on Ti02- and SrO-terminated (100) SrTiOs single-crystal substrates [2.154], of epitaxial niobium films on (110) T1O2 [2.155], the interaction of copper with a (0001) rhenium surface [2.156], and the characterization of radio-frequency (rf) sputtered TiN films on stainless steel [2.157]. 

The catalytic reaction of NO and CO on single crystal substrates, under ultra-high vacuum conditions, has been extensively studied. Neglecting N2O formation and CO desorption, the Langmuir-Hinshelwood mechanism of the NO + CO reaction can be described by the following sequence of steps [16,17] ... 

Crown A, Wieckowski A. 2001. Scanning tunnehng microscopy investigations of mthenium-and osmium-modified Pt(lOO) and Pt(llO) single crystal substrates. Phys Chem Chem Phys 3 3290-3296. 

The other technique is HREELS (high resolution EELS) which utilises the inelastic scattering of low energy electrons in order to measure vibrational spectra of surface species. The use of low energy electrons ensures that it is a surface specific technique, and is often chosen for the study of most adsorbates on single crystal substrates. 

Film deposition on a single crystal substrate can, in principle, lead to the formation of an epitaxed single crystal film. However, relatively limited use has been made of well-epitaxed single crystal films for catalysts for two reasons In many instances the single crystal substrate is only available with very limited dimensions so that the film catalyst is also correspondingly restricted in its area second, in most cases it is either inconvenient or impossible to design the single crystal substrate and the evaporation source... 

Fundamental to forming high quality structures and devices with thin-films of compound semiconductors is the concept of epitaxy. The definition of epitaxy is variable, but focuses on the formation of single crystal films on single crystal substrates. Homoepitaxy is the formation of a compound on itself. Heteroepitaxy is the formation of a compound on a different compound or element, and is much more prevalent. 

The final film thicknesses were increased either by increasing the deposition time or by multilayer deposition. Although the film thickness increases with longer deposition time, the film morphology tends to be poor, as shown in Fig. 7.9. A two-layer technique that used two layers of TBSBCCO films, with an intermediate layer of Ag, improved the film uniformity and morphology, as shown in Fig. 7.10. The deposition process for the multiple layer is as follows (1) Single-crystal substrates are coated with 300 A of Ag (2) TBSBCCO films (0.4-1.3 pm) are prepared by electrodeposition (ED) on Ag/LAO (3) 300 A of Ag are deposited on ED-TBSBCCO/Ag/LAO (4) the second layer of TBSBCCO is electrodeposited (0.4-1.3 pm) on Ag/ED-TBSBCCO/Ag/LAO and (5) the complete two-layer system is reacted. 

Chen, J. Bhattacharya, R. N. 2003. Growth of 1-2 xm thick biaxially textured Bi-2212 films on (1 0 0) LaA103 single crystal substrates by electrodeposition. Physics C 399 171-177. 

In order to establish such a correlation, however, a statistical analysis of a very large number of patterns would be necessary. This is one possible area for application for the pattern recognition techniques mentioned above. For thin single crystal substrates, any epitaxial relationship of the metal particles to the support is clearly evidenced because the patterns are superimposed in nanodiffraction. A comparison can be made of the patterns obtained with the beam on and just off the particle. 

For single crystal substrates which are not in the form of thin films, the techniques of transmission microscopy and nanodiffraction can not be used. For such cases, the techniques of reflection electron microscopy (REM) or its scanning variant (SREM) and reflection high energy electron diffraction (RHEED), in the selected area or convergent beam modes, may be applied (18). 

The rapid developments in the microelectronics industry over the last three decades have motivated extensive studies in thin-film semiconductor materials and their implementation in electronic and optoelectronic devices. Semiconductor devices are made by depositing thin single-crystal layers of semiconductor material on the surface of single-crystal substrates. For instance, a common method of manufacturing an MOS (metal-oxide semiconductor) transistor involves the steps of forming a silicon nitride film on a central portion of a P-type silicon substrate. When the film and substrate lattice parameters differ by more than a trivial amount (1 to 2%), the mismatch can be accommodated by elastic strain in the layer as it grows. This is the basis of strained layer heteroepitaxy. 

Mitchell, C. A. Yu, L. Ward, M. D. Selective Nucleation and Discovery of Organic Polymorphs through Epitaxy with Single Crystal Substrates. J. Am. Chem. Soc. 2001, 123, 10830-10839. 

The problem of surface magnetism and of the magnetic properties of thin metal films supported, or epitaxially grown onto single crystal substrates is also developing with an open interest for the possible exploitation of magnetic supports for information... 

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