Influence of Substrate Temperature and Magnesium Content on Morphology Evolution and Luminescence of Mg-doped ZnO Films

Authors D.V. Myroniuk , L.A. Myroniuk , V.A. Karpyna, L.I. Petrosian, A.I. Ievtushenko

I.M. Frantsevich Institute for Problems in Materials Science, 3, Krzhyzhanovsky St., 03142 Kyiv, Ukraine

Issue Volume 13, Year 2021, Number 5
Dates Received 16 June 2021; revised manuscript received 20 October 2021; published online 25 October 2021
Citation D.V. Myroniuk, L.A. Myroniuk, V.A. Karpyna, et al., J. Nano- Electron. Phys. 13 No 5, 05008 (2021)
PACS Number(s) 68.55.J –, 78.55.Et
Keywords Atmospheric pressure metalorganic chemical vapor deposition, Zinc acetylacetonate, Magnesium acetylacetonate, Scanning electron microscope, Photoluminescence (17) .

Results of studies by scanning electron microscopy and photoluminescence (PL) of structural features and radiative transitions of ZnO:Mg films grown by atmospheric pressure metal-organic chemical vapor deposition (APMOCVD) on silicon substrates are presented. Different ZnO:Mg microstructures from polycrystalline films with smooth morphology to columns and hexagonal rods are effectively formed in a wide temperature range 190-450 °C using two compositions of a mixture of zinc and magnesium (5 and 10 wt. %) acetylacetonates (ZnAA and MgAA, respectively) as precursors. The substrate temperatures have a drastic effect on the crystallinity and morphology of ZnO films. A column shaped ZnO microstructure is formed at a substrate temperature above 350 °C. The MgАА content in the mixture of precursors also affects the morphology of polycrystalline films. At lower substrate temperatures (200-320 °C), grown ZnO:Mg samples with MgAA content of 10 wt. % have a surface morphology characterized by enlarged grains compared to samples grown with MgAA 5 wt. %, whereas high substrate temperatures (350-450 °C) promote to form a surface morphology with rod-like structures in both cases: 5 and 10 wt. % of MgAA content. The growth rate of ZnO structures increases with increasing substrate temperatures. The PL emission spectra of samples with 10 wt. % MgAA demonstrate increased near band edge (NBE) emission and suppress defect level emission compared to samples with 5 wt. % MgAA. Therefore, we can conclude that magnesium acts as an isoelectronic impurity improving NBE PL emission due to gettering of defects. Mg also causes an increase in grain size, improving the crystalline perfection of ZnO:Mg polycrystalline films grown at low substrate temperatures, as well as helps to grow hexagonal rods at higher substrate temperatures. Thus, Mg-doped ZnO microstructures grown in the high temperature range could be an effective photocatalyst.

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