Plasma treatments for the low temperature crystallization of LiCoO2 thin films

As alternatives for the low temperature crystallization of LiCoO2 thin films prepared by radio frequency (rf) reactive magnetron sputtering, two different plasma treatments, microwave and rf plasma treatment, were introduced for the first time. The films deposited at 350 degreesC showed (003) preferred orientation corresponding to a hexagonal layered structure. From X-ray diffraction patterns, it was found that the microwave plasma treatment was effective for enhancing the crystallinity of the as-deposited films. However, the microwave plasma treatment did not enhance electrochemical properties at all, which was associated with the deterioration of surface conditions by the bombardment of energetic particles from the plasma. In the case of rf plasma treatment, the crystallinity improved effectively without severe surface degradation. At the same time, the films treated with rf plasma exhibited relatively good electrochemical properties in comparison with those of bulk LiCoO2 or high temperature annealed LiCoO2 thin films. (C) 2001 The Electrochemical Society.