Short-Period CdO/MgO Superlattices as Cubic CdMgO Quasi-Alloys

New perspective cubic quasi-alloy {CdO/MgO}(m) short-period superlattices (SLs) were grown on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy. The quality of crystals was characterized using high resolution X-ray diffraction and transmission electron microscopy (TEM) techniques. X-ray diffraction confirmed the cubic structure of the samples and the presence of peaks corresponding to the SLs with period ranging from 0.6 to 5 nm. Reciprocal space maps around the (200) and (412) Bragg reflections were collected to analyze the strain in the SLs layers with very high precision. Local lattice parameters were measured by digital processing of experimental HRTEM images. From TEM and small-angle X-ray, thicknesses and growth rates of individual layers of MgO and CdO have been extracted. We found that thicknesses of the CdO and MgO layers influence the measured band gap. Surface roughness parameters for SLs were obtained by both small-angle X-ray diffraction and atomic force microscopy study.