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

Abstract

This paper elucidates the properties of MoOx 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 100W 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 30min to 150min. 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 1μm. 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 MoOx compounds are primarily MoO3 and Mo4O11 as seen from the XRD spectra. However, MoO3 is the dominant phase with preferential orientation of (021). Crystallinity of MoOx increases with annealing time indicating higher diffusion of O2 from atmosphere into Mo film occurs hence yielding thicker MoOx layer. Surface topology probed by AFM indicates homogeneous surface and larger grain clusters are produced as annealing duration has increased.