Extended abstract of a paper presented at Microscopy and Microanalysis 2005 in Honolulu, Hawaii, USA, July 31--August 4, 2005

Extended abstract of a paper presented at Microscopy and Microanalysis 2005 in Honolulu, Hawaii, USA, July 31--August 4, 2005

Thin film amorphous electrolytes with compositions xLi2O:ySiO2:zP2O5 were deposited by single and dual source rf magnetron sputtering and their compositions determined by electron and ion beam techniques. Films containing P but no Si were composed of mainly orthophosphate and some linear chain phosphate anions, whereas single phase films containing Si and P were evidently composed of branched and possibly cyclic and extended network structures. Films with Si/P > 1 appeared to contain two or more amorphous phases. In the range of compositions investigated, the lithium ion conductivity depends mainly on the lithium ion mobility which is sensitive to the structure of the films. An open circuit voltage from 1 to 3 V measured between blocking metal contacts on the electrolyte thin films suggests that the films mightbe electrets.

Thin films of an amorphous lithium-conducting electrolyte were deposited by rf magnetronsputtering of ceramic targets containing Li4SiO4 and Li3PO4. The lithium content of the films was found to depend more strongly on the nature and composition of the targets than on many other sputtering parameters. For targets containing Li4SiO4, most of the lithium was found to segregate away from the sputtered area of the target. Codeposition using two sputter sources achieves a high lithium content in a controlled and reproducible film growth.

Increased interest in ion conducting thin films and thin-film devices is evidenced by the number of papers on this topic presented at the recent Garmisch conference [1[. Magnetically enhanced (magnetron) sputtering [2,3] is an important technique for depositing these as well as other kinds of ceramic thin films. Two advantages of magnetron over conventional diode sputtering are the increased sputtering rate, which is important in the deposition of ceramic materials, and the reduction in electron bombardment of the substrate and growing film. In this paper, we describe our high-vacuum film growth chamber and present the results of tests of this system in fabricating films of lithium ion conducting glass electrolytes, TiS2, and vanadium oxide by reactive dc and rf magnetron sputtering. The results of combining these films into a thin film lithium battery also are discussed.