High crystalline epitaxial thin films of NiO by plasma-enhanced ALD and their properties

Abstract

NiO is an interesting transition metal oxide due to its fascinating properties. High crystalline thin films of NiO are preferred for use in a variety of device applications but are challenging to deposit at low temperatures. We have prepared epitaxial thin films of NiO with [111] as the preferred growth direction on a c-plane sapphire substrate at relatively low temperatures using plasma-enhanced atomic layer deposition (PEALD) exploiting a simple nickel precursor with oxygen plasma. The evolution of crystallinity and surface morphology of the films were studied as a function of substrate temperature. Ultra-smooth NiO films with excellent crystallinity were prepared at 250 °C without the necessity for post-annealing. Different microscopic and spectroscopic methods revealed film characteristics. The magnetic properties of (111) oriented epitaxial NiO films prepared using PEALD are explored for the first time, and they are antiferromagnetic in nature.