A comparative structure and morphology study of Zn(1−x)CdxO solid solution grown on ZnO and different sapphire orientations

Zn(1−x)CdxO solid solutions with a constant Cadmium flow 10 cc have been grown on ZnO, c-, a- and r-plane sapphire substrates using metal organic chemical vapor deposition (MO-CVD). The optical transmission spectra and energy band-gap equation established by Mikano et al. were used to estimate cadmium mole fraction of alloy. Lattice parameters and morphology of these films were examined using high resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) as Cd incorporation and employed substrate. By comparison, we observe significant differences between Cd incorporation and morphologies depending on nature and substrate orientation but the hexagonal wurtzite structure is maintained. Higher Cd incorporation (11.2 at%) is obtained on Zn(1−x)CdxO grown on r-plane sapphire, which is confirmed by the greatest energy shift (340 meV) to lower energy measured by room temperature photoluminescence. However, the lattice parameter c remains unchanged while parameter a is identical for films deposited on ZnO and r-plane sapphire substrates and for those deposited on c- and a-plane sapphire substrates.

► Zn(1−x)CdxO solid solutions with a constant cadmium flow 10 cc have been grown on ZnO, c-, a- and r-plane sapphire substrates using metal organic chemical vapor deposition (MO-CVD). ► Cadmium mole fraction of alloy was determined by optical transmission spectra. ► Thickness are measured from cross-section SEM images. ► Lattice deformation and morphology of these films were examined in detail using high resolution X-ray diffraction, atomic force microscopy (AFM) and scanning electron microscopy (SEM) as employed substrate.