Structure of Diamond Films

Since that time, synthetic diamond films have developed into an important high-tech product employed for many purposes. In comparison to other forms of diamond, the most attractive difference is the facile generation of diamond coated workpieces in almost any desired shape. The preparation of thin layers, for example, for electronic applications, became possible as well only after the development of CVD methods. 

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To a first approximation the temperature sensitivity of the oxidation rate at F < 800°C is less dependent on the structure of diamond (films) then on crystallographic orientation, the data for the diamond faces bracket those of thin layers [47]. 

Crystal Structure and Principal Electrophysical Characteristics of Diamond Films. 216... 

Formation of twin structures on the faces of diamond crystals and films have also been studied by Koidl s group in the early stage of diamond film research [84], So, we begin with reviewing their works, which is then followed by studies of other groups. To make heteroepitaxial diamond films, it is necessary to avoid the formation of twins, and thus the studies on the formation mechanism and morphology of twins are of great importance. 

Although this monograph is mainly concerned with the oriented growth of diamond films, it would be worthwhile to briefly review the atomic structures of diamond surfaces studied by STM and AFM. In this regard, Ref. [137] is comprehensive and will be very useful. Additional descriptions on surface reconstruction are given in Appendix D. 

In 2000, Donnet et al. [44], during synthesis diamond by shock-wave compression, also found the crystalline carbyne in the sample. The crystalline structure of this film was examined by x-ray. The results obtained show that the film is composed of a mixture of diamond and carbyne. 

Single pulse, shock tube decomposition of acetic acid in argon involves the same pair of homogeneous, molecular first-order reactions as thermolysis (19). Platinum on graphite catalyzes the decomposition at 500-800 K at low pressures (20). Ketene, methane, carbon oxides, and a variety of minor products are obtained. Photochemical decomposition yields methane and carbon dioxide and a number of free radicals, which have complicated pathways (21). Electron impact and gamma rays appear to generate these same products (22). Electron cyclotron resonance plasma made from acetic acid deposits a diamond [7782-40-3] film on suitable surfaces (23). The film, having a polycrystalline structure, is a useful electrical insulator (24) and widespread industrial exploitation of diamond films appears to be on the horizon (25). 

Apart from the types of diamond films mentioned so far, further films of sp -hybridized carbon have been described as well. Some of them feature amorphous structures and a large content of hydrogen. Within the scope of this book, these phases will be discussed briefly (Section 6.2.4), whereas further references may be found in the numerous review articles and in the original literature (Chapter 8). 

From examining the spectroscopic characteristics of diamond films, many insights into their structure may be obtained. Most of all the Raman spectroscopy, XRD and electron energy loss spectroscopy (EELS) provide valuable information. Other methods like IR-spectroscopy and XPS shed light on the surface structure. These techniques are supplemented by microscopy methods, for example, by AFM and STM, so altogether the morphology of the films surface can be studied in quite some detail. 

The electrochemical properties of diamond films are very promising. Films doped for better conductivity feature a wide potential window, and owing to their stability and fast response times, etc., they suit very well to a use as electrode material in electroanalysis. Diamond films with their surface being suitably modified further suggest themselves for the analysis of biological material. Due to a low unspecific adsorption, interactions will occur only at those positions carrying the respective structure. This is of considerable interest for the development of the so-called lab on a chip. 

Baranauskas V, Bin Li B, Peterlevitz AC, Tosin MC, Durrant SF (1999) Structure and properties of diamond films deposited on porous silicon. Thin Solid Films 355-356 233-238... 

Figure 8.1 Micrographs of diamond films formed in situ using an ESEM (a) "fuzzy ball" structure and (b) polycrystalline structure. 

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