Very thin (111) NiO epitaxial films grown on c-sapphire substrates by pulsed laser deposition technique

TL;DR

This paper demonstrates the growth of ultra-thin (111) NiO epitaxial films on c-sapphire substrates using pulsed laser deposition, analyzing their structural quality, domain structure, and dislocation densities.

Contribution

It presents a detailed study of the growth conditions and resulting structural properties of very thin NiO films, highlighting their high crystalline quality and low dislocation densities.

Findings

Films as thin as 3 nm with high quality can be grown.

Presence of 60°-rotated triangular domains in the films.

Growth parameters influence dislocation density and strain.

Abstract

(111)NiO epitaxial layers are grown on c-sapphire substrates by pulsed laser deposition (PLD) technique. Structural and morphological properties of the films are studied using in-plane as well as out-of-plane high resolution X-ray diffraction and atomic force microscopy techniques as functions of growth temperature, oxygen pressure and the pulses count of the laser. The study shows that continuous epitaxial films of thickness as low as 3 nm with high crystalline quality, smooth surface and interface morphology can be grown by this technique. The study also reveals the co-existence of 60{\deg}-rotated (111) triangular domains of NiO in the film. The study also evidences the presence of a very low density of 60-degree dislocations in these films. Density of screw and edge dislocations are also estimated to be quite low. It has been found that growth-temperature, oxygen partial pressure and the film thickness can influence differently the density of various dislocation types. These parameters are also found to affect significantly the strain developed in the films.