p-(001)NiO/n-(0001)ZnO heterostructures grown by pulsed laser deposition technique

TL;DR

This study investigates the epitaxial growth and structural properties of NiO/ZnO heterostructures on sapphire substrates using pulsed laser deposition, revealing domain orientations, surface morphology, and electrical characteristics relevant for device applications.

Contribution

It provides detailed analysis of epitaxial growth directions, domain structures, and electrical behavior of NiO/ZnO heterostructures grown by PLD, highlighting the impact of morphology on p-n junction properties.

Findings

NiO and ZnO layers grow epitaxially along specific directions.

NiO films exhibit multiple rotated domains and smooth surfaces.

Rectifying behavior observed in certain heterostructures indicating p-n junction formation.

Abstract

NiO/ZnO heterostructures are grown on c-sapphire substrates using pulsed laser deposition (PLD) technique. X-ray diffraction study shows that the ZnO layer epitaxially grows along [0001]-direction on (0001)sapphire surface as expected. While, the epitaxial NiO film is found to be deposited along [001]-direction on the (0001)ZnO surface. Moreover, the presence of three (001)NiO domains laterally rotated by 30{\deg} with respect to each other, has also been observed in our NiO films. The study reveals the continuous nature of the NiO film, which also possesses a very smooth surface morphology. In a sharp contrast, ZnO films are found to grow along [0001]-direction when deposited on (111)NiO layers. These films also show columnar morphology. (001)NiO/(0001)ZnO layers exhibit the rectifying current-voltage characteristics that suggests the existence of p-n junction in these devices. However, the behavior could not be observed in (0001)ZnO/(111)NiO heterojunctions. The reason could be the columnar morphology of the ZnO layer. Such a morphology can facilitate the propagation of the metal ions from the contact pads to the underlying NiO layer and suppress the p-n junction effect.