Molybdenum nitride thin films synthesized by microwave electron cyclotron resonance – Assisted reactive pulsed laser deposition

Abstract

Molybdenum nitride thin films were deposited using a hybrid plasma system. This system results from the combination of a stationary continuous plasma, created by a microwave electron cyclotron resonance discharge in nitrogen atmosphere and a pulsed plasma produced by the laser ablation of a molybdenum metallic target. The plasma parameters were measured by Langmuir probes, and the type of chemically excited species were detected by optical emission spectroscopy. The results indicate that the hybrid plasma is more efficient than the laser ablation or microwave discharge processes alone. X-ray diffraction showed the presence of the δ-MoN (hexagonal) phase with a preferred orientation that changes depending on the experimental conditions. Films deposited using the laser ablation process without the presence of the microwave plasma were mainly composed by metallic molybdenum, as seen by X-Ray Diffraction. X-ray photoelectron spectra measurements showed that the nitrogen content in the samples grown by the hybrid plasma process is significantly higher than in those grown with the conventional laser ablation process. The hardness values ​​of the MoN films grown by the hybrid system increased from 19 to 24 GPa as a function of the mean kinetic energy of the ions formed in the laser ablation plasma. All the films show superconductivity, with a Tc-onset from 5.1 to 7.2 K, depending on the nitrogen content.