Study of Nickel Oxide Thin Films by Atomic Layer Deposition
Date Issued
2011
Date
2011
Author(s)
Lee, Wei-Chang
Abstract
This study develops an atomic layer deposition (ALD) process to deposit NiO thin films, using ozone as an oxidizing source and nickelocene (Ni(Cp)2) as a Ni-containing precursor. The ALD process window was found to be 150~250℃ with a deposition rate of ~0.7 A per cycle. XPS analysis revealed that the films were composed of nearly stoichiometric, Ni/O ratio = 0.95, with < 4% carbon content, indicating thorough reaction and low level of Ni vacancies which are typical of NiO films. GIXRD, SEM and AFM analyses show that the films were cubic polycrystalline, with NaCl-type structure, with ~12 nm crystal size and smooth surface. Additionally, the ALD NiO films were found to be effective gas-diffusion barriers when deposited on polymer substrates, with similar gas permeability to those of other crystalline metal oxide films by ALD, such as ZnO and HfO2. In terms of optical transparency, the ALD NiO films with 70nm thickness showed > 65% light transmittance across the visible light wavelength. From the visible light spectrum, the optical band gap of the ALD NiO was estimated to be 3.47eV. In terms of electrical properties, the ALD NiO films contained very low level of carrier (hole) concentration and thus were highly electrically insulating. This was attributed to the nearly stoichiometric Ni/O ratio of the films, which minimized the amount of holes associated with Ni vacancies or interstitial O atoms.
Subjects
Nickel oxide
Atomic layer deposition
P-type transparent semiconductor
Thin films
Nickelocene
Type
thesis
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