Properties of Hydrocarbon Layers

Typical properties of plasma-deposited a-C H layers are summarized in Table 11.1. 

C H layers have a limited thermal stability in the sense that they decompose at elevated temperature even in vacuum. The released product spectrum and the onset temperature for decomposition depend sensitively on the layer structure, in particular, the initial hydrogen content [29,30]. Hard a-C H layers with a typical H content of about 30% (see Table 11.1) start to decompose around 700 K with two distinct effusion maxima at about 800 and HOOK [29,30]. The product spectrum is dominated by H2 with minor contributions of CH4 and some higher hydrocarbons (C.. H y). These results are in good agreement with published data on ion-beam deposited C H layers [31,32], ion-bombarded pyrolytic graphite [33], and other plasma- 

---