Transitions in morphology observed in nitrogen/methane-hydrogen depositions of polycrystalline diamond films

In this work, we report on a series of transitions in morphology and textur e as 5-1000 parts per million of nitrogen were added to 2% and 1% methane-h ydrogen depositions of polycrystalline diamond films. Five results are repo rted. (1) The threshold for transition into the {100}-faceted morphology oc curred at lower parts per million nitrogen for the 1% versus the 2% methane -hydrogen series, opposite from the transition thresholds previously report ed. (2) At 1000 parts per million nitrogen the film quality of both series had not yet seriously degraded. (3) A well defined sequence of intermediate texture transitions as a function of increasing parts per million nitrogen was observed for both series. (4) A pretransition morphology of large crys tallites interspersed among microcrystalline material directly preceding th e transitions to the {100}-faceted morphology was observed for both series. (5) A layered growth and/or etched morphology at high nitrogen concentrati ons was observed for both series. We discuss these observations in terms of the possible influence of our deposition conditions on the accessibility o f diamond growth parameter space and chemistry, including possible dynamica l effects of the temperature gradients. (C) 2001 American Institute of Phys ics.