Tailoring the physical properties of low dimensional MgO nanostructures using vapor transport deposition

In this study, low-dimensional (LD) MgO nanostructured thin films with three different morphologies, namely,
nanowires (NWs), nanotubes (NTs) and nanoparticles (NPs) were fabricated by a vapor transport method on
quartz and silicon substrates under optimum growth conditions. It was found that the deposition parameters
have great influences on the morphology, optical, photoluminescent, electrical, gas sensing and magnetic behavior
of the resulting products. X-ray diffraction analysis illustrated that all three LD MgO nanostructures have
five expected Bragg peaks of cubic MgO phase purity with well crystalline nature. The morphology and diameter
of LD MgO nanostructures were probed by scanning electron and transmission electron-microscopes. The optical
band gap values for LD MgO nanostructure films varies between 3.65 eV and 3.95 eV depending on growth
conditions. It was found that all MgO films exhibit two distinguishing PL peaks related to the near band edge
luminescence of LD MgO nanostructures and defect levels produced by oxygen vacancies, respectively. It was
found that the dependence of electrical conductivity on film morphology can be attributed to the defect levels
produced by O2- ion vacancies during the synthesis process. NH3 gas sensing efficiency of LD MgO nanostructures
with various morphologies were carried out at different operating temperatures from 25 °C to 300 °C.
The MgO film with NWs structure has the highest sensor response value of 27 at 100 °C and the film with NPs
structure has the lowest response value of 12 at 150 °C. Ferromagnetic order has been recorded for all
morphologies at room temperature with clear hysteresis loop and different magnetic parameters depending on
growth conditions. Thus, our results present a direct route for the growth of high-quality and diverse LD MgO
nanostructures developed via vapor transport for many technological applications.