ZnMgO/ZnO Core-Shell Structures for Gas Sensing

Co-axial Zn_1−xMg_xO core, ZnO shell structures were grown using metal organic chemical vapor deposition (MOCVD), with Mg mole fractions of 2, 5 and 10%. The co-axial core shell structure, with the respective Mg concentration is verified using scanning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive spectroscopy (EDS). The response times (ṟise time and fall time) of the devices, after being exposed to methanol, varied with Mg mole fraction at the core, r-0.17s and, f-0.37s & f-0.48s for 2% Mg, r-0.81s and, f-5.98s & f-0.89s for 5% Mg and r-0.33s and f-0.13s for 10% Mg. The sensitivity of the devices at room temperature increased with the increment of Mg mole fraction at the core, 25%, 48% and 50% with Mg concentration of 0.02, 0.05 and 0.1, respectively, under high concentration of methanol. The estimated activation energy, corresponds to doubly charged oxygen vacancy (Vo²⁺).