In Situ Modification of RF Sputter-Deposited Lithium Nickel Oxide Thin Films by Plasma Irradiation

Abstract

Lithium nickel oxide thin films were deposited by sputter deposition. The films were in situ-modified using low-temperature inductively coupled plasma (ICP) irradiation. The technique uses a built-in radio frequency (rf) coil to generate an ICP plasma confined close to the substrate. The ions in the ICP can be drawn to the substrate by negative bias. This enables precise control of both bombarding ion flux (by rf power) and energy (by substrate bias). Varying the flux and energy of bombarding ions modifies the film properties. The crystal structure can be characterized as the layered oxide structure or rhombohedrally distorted NiO-type structure depending on Li content. The films modified by different conditions of plasma irradiation exhibited crystallography changes and texturing. The film composition was measured by ICP atomic emission spectroscopy and X-ray photoelectron spectroscopy. The film crystallography was characterized by X-ray diffraction. The film morphology modified by the plasma irradiation was observed by scanning electron microscope. Half-cells made of the lithium nickel oxide thin films were fabricated and the discharge curves measured to compare the electrochemical properties of the in situ-modified films. The films treated by in situ anneal were also prepared for comparison. © 2004 The Electrochemical Society. All rights reserved.