Growth of MoO x nanobelts from molybdenum bi-layer thin films for thin film solar cell application

Abstract This paper elucidates the properties of MoO x nanobelts grown by air annealing that is executed on DC-sputtered Mo bi-layers. Molybdenum thin films were deposited by DC Magnetron sputtering with DC power of 100 W at room temperature. First layer was sputtered at higher pressure to promote adhesion meanwhile second layer was sputtered at lower pressure to increase the conductivity of the film. Sputtered Mo film was annealed at 500 °C in air for duration ranging from 30 min to 150 min. The grown stacked structures were then characterized by Scanning Electron Microscopy (SEM), X-Ray Diffractometer (XRD), Atomic Force Microscopy (AFM) and Hall Effect measurement to elucidate the structural and electrical properties. The thickness of sputtered Mo films was in the range of 1 μm. All deposited Mo films passed the “Scotch Tape” indicating good adhesion with soda lime glass substrate and preferential crystal orientations were found to be (110) and (211) from XRD measurement. The formed MoO x compounds are primarily MoO 3 and Mo 4 O 11 as seen from the XRD spectra. However, MoO 3 is the dominant phase with preferential orientation of (021). Crystallinity of MoO x increases with annealing time indicating higher diffusion of O 2 from atmosphere into Mo film occurs hence yielding thicker MoO x layer. Surface topology probed by AFM indicates homogeneous surface and larger grain clusters are produced as annealing duration has increased.