Polymerization in nanocrystalline diamond films by oxygen incorporation

Structure and resistivity of nanocrystalline diamond films deposited using microwave Ar-rich/O-2/CH4 plasmas have been examined as a function of the O-2/CH4 ratio from 0 to 0.53. Addition of O-2 to Ar-rich/CH4 plasmas likely reduced the density of C-2 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 sp(2)-bonded, disordered carbon and its intensity was a little enhanced by the 0, addition, while the average size of sp(2)-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 10(4) Omega center dot m with a small O-2 addition (1.2 vol.-% in total pressure), providing novel sensor and storage applications based on oxygen incorporation and desorption.