Ambient temperature synthesis of polycrystaline thin films of lithium cobalt oxide with controlled crystallites' orientations

摘要

Polycrystallien thin films of lithium cobalt oxide have been deposited bya porcess which we have named, ion beam directed assembly. It is similar to ion asisted deposition or ion beam assisted deposion, but the major difference is that in IBDA the ion beam directs, via the vector momenta ofthe ions, rather than merely assists, the growth. Hence, we also term the process directed asembly to distinguish it from self assembly. Also, in directed asembly the ions may or may not become an integral part of the film's composition. In this paper we wish to show that the IBDA process may be capable of ocntrolling microstructure, e.g., in the case of polycrystallien films, control the orientations of the crystallites. FOr LiCoO_2 we have observed this in two ways-by X-ray analysis, and electrochemically ,by lithium diffusivity measurements. I nparticular, we have observed increased lithium diffusivities in IBDA deposited films as compared to that found for rf sputter deposited films. iN addition, the coulometric titration characteristics of an IBDA deposited Li_(1-y)CoO_2 are very similar to those of sputtered deposited films.