Conductive and resistive nanocrystalline diamond films studied by Raman spectroscopy

This paper shows what structural properties of amorphous non-diamond phases in nanocrystalline diamond films are responsible for the transition from resistive to conductive films. The films incorporated with nitrogen, oxygen, and hydrogen are prepared by microwave plasma chemical vapor deposition using Ar-rich gas mixtures. The amount, composition, and bonding properties of non-diamond phases are studied mainly by Raman spectroscopy and compared with the electrical resistivity of the films. The addition of N(2) gas decreases the resistivity down to the order of 10(-2) Omega cm for deposition temperatures above a threshold of similar to 1100 K. Non-diamond phases for high n-type conductivity are characterized by graphitic components with improved sp 2 bond angle order for trivalent carbon atoms in addition to C=N bonds. The addition of O(2) or H, gas promotes incorporation of oxygen or hydrogen into the films, not preferential etching of non-diamond phases. The resistivity increases or decreases largely by oxygen or hydrogen incorporation, respectively, then inversely changes by thermal annealing due to the deoxidization and dehydrogenation. (C) 2006 Elsevier B.V. All rights reserved.