Electrically Conducting Diamond Films for Wear and Erosion Resistance

Wear resistant electrically conducting diamond coatings are desired in extending the lifetime of components in electric rocket thrusters for space applications. These may include hollow cathodes, various electrode surfaces, and extraction grids, to name only a few. Although several methods exist for the deposition of diamond coatings, many of these processes are limited in their ability to produce doped diamond films with reproducible quality. In this Phase I effort, we will demonstrate the feasibility of producing diamond that is doped using two different deposition techniques. We will first use a modified hot filament CVD method to deposit doped diamond films from acetone/methanol mixtures containing the p-type dopant as a boron-containing compound, and measure their electrical resistivities. Since large area deposition at high rates will be desired, we will also attempt to use a DC-arcjet to deposit boron-doped diamond films using boron containing precursors. Analytical instrumentation such as scanning electron microscopy and Raman spectroscopy will be used to characterize the films. Preliminary electrical resistivity measurements will be performed on films produced using a four-point probe. We expect to scale up the technique in Phase II to deposit doped diamond coatings over prototype electrode and insulator components for extensive evaluation so that the technique can be adapted for production during Phase III.