Thin film growth chemical characterization

The principal applications of REELS are thin-film growth studies and gas-surface reactions in the few-monolayer regime when chemical state information is required. In its high spatial resolution mode it has been used to detect submicron metal hydride phases and to characterize surface segregation and difRision as a function of grain boundary orientation. REELS is not nearly as commonly used as AES orXPS. 

The different growth modes discussed above have been exemplified also from structural studies. Froment and Lincot [247] used structural characterization methods, such as TEM and HRTEM, to determine the formation mechanisms and habits of chemically deposited CdS, ZnS, and CdSe thin film at the atomic level. These authors formulated reaction schemes for the different deposition mechanisms and considered that these should be distinguished to (a) atom-by-atom process, providing autoregulation in normal systems (b) aggregation of colloids (precipitation) ... 

As we mentioned, oxide surfaces are important in the field of nanocatalysis by supported metals. In practical applications, the support has the crucial role of stabilizing small metallic particles, which act as the actual catalysts in a chemical process. Once the oxide surface is sufficiently well characterized, one can deposit small metal clusters and study their reactivity as a function of the support, of the metal, of the size of the cluster, etc. In this way, complex catalytic processes can be divided into a series of substeps, which allow a more detailed microscopic characterization. Despite the fact that only recently well-defined metal clusters have been deposited under controlled conditions on oxide surfaces and thin films, great advances have been obtained in the understanding of the mechanisms of adhesion and growth of the metal particles to the oxide surface. In this process, the role of theory is quite substantial. 

Figure 34 Typical structure of a thin-film medium [84]. (Reproduced from Journal of Applied Physics, 77(11), Bormett, R. W., et aL, Ultraviolet Raman spectroscopy characterizes chemical vapor deposition diamond film growth and oxidation, pp. 5916-5923. Copyright 1995, with permission from the author and the American Institute of Physics.)... 

The iron-rich ceramics from films PS-6-PFS function as catalysts for the growth of single-walled carbon nanotubes (SWCNT). Typically, thin films were self-assembled and treated with UV-ozone to remove organic materials and subsequently used for the simple one-step chemical vapor deposition (CVD) growth of SWCNTs. The resulting SWCNTs were characterized by... 

Paley, M.S., D.O. Frazier, H. Abeledeyem et al. 1992. Synthesis. Vapor growth, polymerization, and characterization of thin films of novel diacetylene derivatives of pyrrole. The use of computer modeling to predict chemical and optical properties of these diacetylenes and poly(diacetylenes). JAm Chem Soc 114 (9) 3247-3251. 

The ability to in situ characterize the growth and properties of organic thin Aims enables us to better understand the associated underlying mechanisms. Many techniques allow such studies. For films a few MLs thick the techniques should be sufficiently surface sensitive. In situ is too often confused with real-time techniques. Real-time clearly means that the physical or chemical phenomena are studied without interruption of the process. Indeed, this has to be done in situ during growth. However, some in situ techniques, because of the experimental geometry. 

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