ZnO is an attractive material, especially due to exciting optical properties. Therefore, its application fields can be expanding from the SAW devices to the light emitting diodes (LEDs).

In this work, we first investigated the surface morphology of ZnO epilayers grown on C-, M-, A- and R-plane sapphire by metalorganic chemical vapour deposition (MOCVD) at low pressure and high temperature. Diethylzinc and N₂O were used as the zinc and oxygen precursors respectively. The carrier gas was helium. The varying growth parameters were the substrate temperature, the reactor pressure and the VI/II partial pressure ratio. ZnO layers were characterised by atomic force microscopy (AFM), scanning electron microscopy (SEM), X- ray diffraction (rocking curve), Raman spectroscopy and photoluminescence.

Figure 1 shows different surface morphologies of ZnO layers grown on sapphire substrates. On R-plane, SEM image exhibits a rather smooth surface, and the mechanism of growth of ZnO is "quasi 2D". On C- plane, the surface is rough and shows 3D islands, and, on M-plane, a high density of defects can be observed.

Subsequently, we studied the surfactant effect of a triethyl-antimony (TESb) flow on the surface morphology. Whereas the ZnO  film grown on C-sapphire substrate exhibits a rough surface, the  ZnO:Sb layer shows a smooth surface.

Figure 1 : SEM images of ZnO layers grown on R-plane sapphire, M-plane sapphire,C-plane sapphire, and  ZnO:Sb grown on C-plane sapphire.

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1. Structural characterizations of ZnO based one-dimensional nanostructures grown by MOCVD
2. Nitrogen-doped and Antimony-doped ZnO thin layers grown by MO-VPE
3. Effect of Chlorine doping on electrical and optical properties of ZnO thin films