Fracture toughness of the interface between CVD diamond film and silicon substrate in the relation with methane concentration in the source gas mixture

Diamond films produced by chemical vapor deposition (CVD) have been reporte d to show various excellent properties. However, low toughness of diamond f ilms, especially the interface between the films and substrates, has been a severe problem. In order to find the dominant factors to control the adhes ive strength of CVD diamond films, we obtained diamond films with various c rystalline structures deposited on silicon (100) substrates under various m ethane concentrations in the source gas mixture. The toughness of the inter face between the diamond film and silicon substrate was evaluated for the f irst time by a recently developed method. The toughness showed an interesti ng behavior with respect to the variation of methane concentration. The obt ained results were quantitatively compared to the data already obtained for the case of CVD diamond particles deposited on silicon substrates. (C) 200 1 Elsevier Science B.V. All rights reserved.