Phase control of MoxN films via chemical vapor deposition

Abstract

Polycrystalline single phase (γ-Mo2N and δ-MoN) and two phase (γ-Mo2N + δ-MoN) films have been deposited via chemical vapor deposition on prepared 50 μm thick polycrystalline Ti substrates using both molybdenum pentachloride (MoCl5) and molybdenum hexacarbonyl (Mo(CO)6), diluted in either N2 or Ar, and anhydrous ammonia (NH3) in a cold-wall, vertical pancake-style reactor. X-ray diffraction data showed that polycrystalline, single phase γ-Mo2N films were deposited between 400-450°C with the MoCl5 precursor and between 350-500°C with the Mo(CO)6 precursor. Above these respective temperatures and up to 700°C, a two-phase mixture of γ-Mo2N and δ-MoN was observed. At 700°C, single phase δ-MoN films were deposited by employing the Mo(CO)6 precursor and 1.5 slm of NH3; however, a two phase mixture of ≈ 95 at.% δ-MoN and ≈ 5 at.% γ-Mo2N was observed in films prepared using the MoCl5 precursor. Regardless of the precursor, decreases in the NH3 flow rate were matched by decreases in δ-MoN percentages at each temperature where δ-MoN was present. Increasing in the deposition rate also resulted in decreasing δ-MoN percentages at each deposition temperature. Scanning electron micrographs (SEM) indicated that the porous micro structure of the films were dependent on both the deposition temperature and the precursor employed. Energy dispersive X-ray (EDX) data indicated that films deposited at and above 400°C with the MoCl5 precursor did not contain detectable levels of chlorine. Higher carbon levels were detected in films deposited with the Mo(CO)6 precursor than with the MoCl5 precursor. © 1998 Elsevier Science S.A. All rights reserved.