Electrical resistivity, wettability, and structural properties of oriented columnar Mo thin films

This work reports on the effects of oblique angle deposition on the microstructure, electrical resistivity, and wettability of molybdenum (Mo) thin films. DC magnetron sputtering deposits Mo on silicon wafers while the substrate inclination angle varies from a = 10 degrees to 80 degrees. A constant film thickness of 800 nm is prepared, whereas the deposition angle alpha is systematically changed from 0 to 80 degrees. Thin film crystalline structure is analyzed by Xray diffraction and shows that for a substrate inclination angle lower than 60 degrees, the (110) peak of the bcc Mo phase becomes more pronounced. Grain size and crystallinity decrease as the deposition angle increases, particularly for alpha higher than 60 degrees, from 12.4 to 8.9 nm. Morphological characteristics of Mo thin films show a significant voided architecture as the substrate inclination angle rises. Oxygen enrichment is also obtained, and Mo films become less conductive with an electrical resistivity increasing by two orders of magnitude as the substrate inclination angle reaches 80 degrees. Using the contact angle technique, it is found that Mo films are hydrophobic with an improved wettability as an angle tends to be glancing, the values of surface free energy were increased from 48.1 and 62.1 mN m-1. Results indicate that rather than adjusting the composition of thin films, it is possible to affect their properties by modifying their nanostructured design.