SYNTHESIS, STRUCTURE AND MECHANICAL-PROPERTIES OF NANOSTRUCTURED MOSI2NX

A systematic study of the synthesis-structure-mechanical properties re lationship is reported for MoSi2Nx films. MoSi2Nx films with nitrogen content x ranging between 0 and 4.2 were prepared by sputtering techni que. Cross-sectional transmission electron microscopy was used to exam ine the as-sputtered and annealed microstructures when exposed to diff erent annealing conditions. Nanoindentation was employed to characteri ze the mechanical response of the materials as a function of the struc tural changes. As-sputtered MoSi2Nx films exhibit an amorphous structu re. Annealing at 900 degrees C causes different microstructural change s depending on the nitrogen content. The resulting microstructure cons ists of nanocrystalline C11(b)-MoSi2 for x=0, nanocrystalline C40 phas e for x=1.5 and amorphous for x=2.95 and 4.2. The hardness of the as-s puttered MoSi2Nx films increases with nitrogen content to a maximum of 17.8 GPa (x similar to 3) and then decreases for higher nitrogen cont ents. Annealing at 500 degrees C and 900 degrees C, respectively, resu lts in an increase in hardness. The rate of increase decreases with in creasing nitrogen concentration. Increase in modulus is strongly relat ed to the crystallization process, which is also affected by the nitro gen content in the MoSi2Nx films. These results suggest the possibilit y of engineering MoSi2Nx by varying the composition and heat treatment to produce suitable materials properties for different materials appl ications.