Designing Various Self-Assembled ZnOx Quantum Dots/Islands on Silicon with Distinctive Characteristics by Magnetron Sputter

Abstract

Three types of self-assembled ZnOx quantum dots (QDs) or islands on silicon substrates with distinctive morphologies were successfully synthesized using various growth schemes in a simple magnetron sputter. If hydrogen/argon was employed as the sputtering gas under negative substrate bias, the growth started from surface pit formation, leading to self-aligned cone shaped ZnOx QDs with composition, x, being linearly dependent on substrate bias, providing an ideal platform for defect engineering and related application. Intriguingly, if there is no substrate bias applied, the most energetically favorable ZnOx hexagonal pyramids were formed on the surface, in quasi-epitaxy with the Si substrate. Spherical stoichimetric ZnO QDs in a narrow size range were synthesized when oxygen was particularly introduced, and these exhibited true quantum confinement effects, evidenced by a blue shift of the UV emission in the photoluminescence spectrum. This work facilitates the development of controllable ZnO QDs, and, most importantly, sheds light on the quick implantation of ZnO QDs into devices by an industrially compatible sputter.