Crystallization of lithium cobalt oxide thin films by radio-frequency plasma irradiation

Abstract

The crystallinity of lithium cobalt oxide thin films deposited by the radio-frequency (rf) reactive magnetron sputtering method has been improved by the rf plasma irradiation method. Compared with conventional thermal annealing, reaction to form crystalline lithium cobalt oxide via rf plasma irradiation is fast and does not need any additional external heat supply. It is found that the nucleation and the growth reactions are determined during the film deposition and the rf irradiation, respectively. The film composition does not change significantly, and severe mechanical damages such as resputtering or etching phenomena do not appear after the irradiation. A model showing the process of the crystallization by rf plasma irradiation is suggested on the basis of phenomenological analyses using secondary electron microscopy, high-resolution transmission electron microscopy, etc.

Amorphous LiCoO2 thin films on Li1+x+yAlxTi2−xSiyP3−yO12 prepared by radio frequency magnetron sputtering for all-solid-state Li-ion batteries

“…As a result, the as-deposited film can be considered to have a locally crystalline structure within the amorphous matrix. Although the exact mechanism of the nucleation and crystallization of the crystallized component is not clear yet, it may be related to the RF plasma irradiated on the film [37]. Similar phenomenon was observed in the high-temperature annealed LiCoO 2 thin film [38].…”

Highly Oriented Growth of Pulsed-Laser Deposited LiNi0.8Co0.2O2 Films for Application in Microbatteries

“…Improved understanding of the synthesis processes and correlation of electrochemical properties with structures enhances our ability to engineer the microstructure and stability and to tune the conditions to produce low-dimensional oxides with excellent properties and enhanced performances. Furthermore, thin film preparation of LiNi 1 - y Co y O 2 (0 < y <1) system with controlled structure and desired properties is very difficult using conventional evaporation methods because of loss of either lithium or oxygen during deposition. − Several post-deposition methods were also proposed to improve the crystallinity or homogeneity of the oxide films …”

The Effects of Thermal and Atmospheric Pressure Radio Frequency Plasma Annealing in the Crystallization of TiO2 Thin Films

“…In conventional furnace annealing, this energy barrier is overcome by thermal energy externally supplied. In RF plasma irradiation, however, the initial energy state is activated to a higher energy level as a result of momentum transfer from the plasma, so the activation energy barrier is reduced, as illustrated, and the film is crystallized effectively by the RF plasma irradiation [28]. Both the XRD and Raman results show similar results that the RF plasma treatment enhanced the crystallization of TiO2 film.…”