Ag nanoparticle decorated molybdenum oxide structures: Growth, characterization, DFT studies and their application to enhanced field emission

We report a simple single step growth of α-MoO₃ structures and energetically suitable site specific Ag nanoparticle (NP) decorated α-MoO₃ structures on varied substrates, having almost similar morphologies and oxygen vacancies. We elucidate possible growth mechanisms in light of experimental findings and density functional theory (DFT) calculations. We experimentally establish and verified by DFT calculations that the MoO₃(010) surface is a weakly interacting and stable surface compared to other orientations. From DFT study, the binding energy is found to be higher for (100) and (001) surfaces (∼-0.98 eV), compared to the (010) surface (∼-0.15 eV) and thus it is likely that Ag NP formation is not favorable on the MoO₃(010) surface. The Ag decorated MoO₃ (Ag-MoO₃) nanostructured sample shows enhanced field emission properties with an approimately 2.1 times lower turn-on voltage of 1.67 V μm^-1 and one order higher field enhancement factor (β) of 8.6 ×10⁴ compared to the MoO₃ sample without Ag incorporation. From Kelvin probe force microscopy measurements, the average local work function (Φ) is found to be approximately 0.47 eV smaller for the Ag-MoO₃ sample (∼5.70 ±0.05 eV) compared to the MoO₃ sample (∼6.17 ±0.05 eV) and the reduction in Φ can be attributed to the shifting Fermi level of MoO₃ toward vacuum via electron injection from Ag NPs to MoO₃. The presence of oxygen vacancies together with Ag NPs lead to the highest β and lowest turn-on field among the reported values under the MoO₃ emitter category.