Structure and resistivity of nanocrystalline diamond films deposited using microwave Ar-rich/O2/CH4 plasmas have been examined as a function of the O2/CH4 ratio from 0 to 0.53. Addition of O2 to Ar-rich/CH4 plasmas likely reduced the density of C2 radicals due to loss reactions of O atoms with CH4 and CHx radicals. The Raman peak of diamond at 1332 cm-1 was overlapped by the D peak of sp2-bonded, disordered carbon and its intensity was a little enhanced by the O2 addition, while the average size of sp2-bonded carbon clusters in nondiamond phases was increased. Oxygen was incorporated into the films in forms of C-O bonds, which bridged the carbon clusters themselves, and formed polymer-like, large-unit structures. The resistivity of the films was drastically increased from the order of 10-4 up to 104 Ω · m with a small O2 addition (1.2 vol.-% in total pressure), providing novel sensor and storage applications based on oxygen incorporation and desorption. A figure is presented. Decomposition of a Raman spectrum showing the diamond, D and G modes of amorphous carbon, and trans-polyacetylene peaks. The insert represents a typical SEM image showing a film surface.
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