Low temperature chemical vapor deposition of superconducting molybdenum carbonitride thin films

Thin films of molybdenum carbonitride, MoC _x N _y , are deposited by low temperature chemical vapor deposition from Mo(CO) ₆ and NH ₃ in the temperature range 150-300 °C. At a substrate temperature of 200 °C and Mo(CO) ₆ pressure of 0.01 mTorr, the composition varies from MoC _0.48 N _0.20 to MoC _0.36 N _0.33 (i.e., greater nitrogen and less carbon content) upon increasing the ammonia pressure from 0.3 to 3.3 mTorr. At a constant Mo(CO) ₆ pressure of 0.01 mTorr and an NH ₃ pressure of 2 mTorr, the composition varies from MoC _0.50 N _0.30 to MoC _0.12 N _0.40 with increasing substrate temperature from 150 to 300 °C. Selected films grown at substrate temperatures of 150, 200, and 250 °C are superconducting with critical temperatures of 4.7, 4.5, and 5.2 K, respectively. Grazing incidence x-ray diffraction data indicate that the films are crystalline and isomorphous with the cubic phases of Mo ₂ N and Mo ₂ C. With a forward-directed flux of precursors toward the surface, film growth is highly conformal in microtrenches of aspect ratio 6, with step coverages of ∼0.85 and 0.80 at growth temperatures of 150 and 200 °C, respectively.