UV exciton emission enhanced by plasma treatment over ZnO/MgO core/shell nanowires

ZELAYA, MARÍA PRISCILA; VEGA, NADIA CELESTE; DI DONATO, ANDRES; BONAPARTE, JUAN; STEREN, LAURA BEATRIZ; COMEDI, DAVID MARIO; TIRADO, MONICA CECILIA

Port Louis

Encuentro; The 5th EMN Mauritius Meeting 2019: Computation and Theory & Nanowires; 2019

International Conference on Energy, Materials and Nanotechnology (EMN); Université d´avant-garde (INRS) and Institute of Fundamental and Frontier Sciences: UESTC

Compared to other semiconductors materials with a wide band gap, ZnO exhibits very interesting properties such as having an ultraviolet (UV) band width of 3.3 eV of energy and a large exciton binding energy of ~60 meV, which results in more efficient exciton emission at room temperature. These properties make ZnO a great candidate for the development of optoelectronic devices in the UV range [1].ZnO nanowires (NWs) have a large surface/volume ratio, so the presence of surface defects provides an unwanted luminescence in the visible range, impairing its application in optical devices in the UV range. To overcome this problem, it is possible to coat the NWs with different thicknesses of another semiconductor, such as MgO, to passivate the surface and avoid surface defects, thereby improving UV emission, as reported in previous publications [1-3].In this work, ZnO NWs were grown on p-type Si substrates by the hydrothermal method. In a second stage, conformal MgO coatings at two different thicknesses were grown on the NWs by vapour transport deposition. The morphological characterization of the NWs was carried out by scanning electron microscopy (SEM). Photoluminescence (PL) spectroscopy measurements were performed at room temperature.In order to remove portions of the MgO shell at the NW tips for electrical contacts, a plasma treatment over ZnO/MgO core/shell nanostructures was performed. Surprisingly enough, after few minutes of exposure to the Ar+ treatment, strong increases (as a factor of 200) of the NW ultraviolet-to-visible emission intensity ratio were observed.