General Considerations on the Structure of Diamond Films

Diamond films are a mono- or polycrystalline layer of diamond with a thickness (usually) in the range of micrometers and a comparatively wide dilation regarding the other two directions in space. Thus a-generally coherent-film is obtained. It can either be deposited on a substrate or can exist as a homoepitaxially grown layer or a free-standing structure. 

In the process, a high concentration of carbon in the gas phase of the reactor favors high a-values, whereas increasing the substrate temperature or reducing the pressure leads to decreased ot-values and, consequently, to a film structure characterized by cubic crystaUites. 

Contrary to single crystalline diamond films, the polycrystaUine layers contain a much larger portion of sp -hybridized carbon. This can be attributed to the large number of grain boundaries and has considerable influence on the electronic properties of these films (Section 6.4.2). 

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). 

Nanoctystalline diamond film, SEM-image (a) top view, (b) side view ( AlP 

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