J Electroceram (2006) 17:1023–1030 DOI 10.1007/s10832-006-8976-3 Effects of sputtering pressure on the characteristics of lithium ion conductive lithium phosphorous oxynitride thin ﬁlm Ho Young Park · Sang Cheol Nam · Young Chang Lim · Kyu Gil Choi · Ki Chang Lee · Gi Back Park · Seong-Rae Lee · Heesook Park Kim · Sung Baek Cho Received: 30 June 2005 / Revised: 20 April 2006 / Accepted: 28 April 2006 C  Springer Science + Business Media, LLC 2006 Abstract Lithium phosphorous oxynitride(Lipon) thin ﬁlms as a lithium ion conductive electrolyte were prepared by radio frequency reactive sputtering in N 2 plasma. The properties of the amorphous Lipon solid electrolyte were investigated as a function of N 2 pressure during reactive sputtering. The ionic conductivity and the electrochemical stability of Lipon thin ﬁlms improved drastically as the N 2 pressure decreased. The ionic conductivity closed to 10 −6 S cm −1 and obtained a sta- bility window of 1.0–5.0 V with an N 2 pressure of 5 mTorr, where the number of nitrogen bonds between the phosphate groups were more than those formed at higher pressure. It was possible to fabricate the Li//LiCoO 2 complete thin ﬁlm battery using this Lipon solid electrolyte, which exhibited excellent discharge characteristics close to the theoretical ca- pacity (ca. 69 uAhcm −2 −um −1 ) and showed a considerably high rate capability. Keywords Lipon . Solid electrolyte . Thin ﬁlm battery . Sputtering . Nitrogen pressure H. Y. Park · S. C. Nam () · Y. C. Lim · K. G. Choi · K. C. Lee · G. B. Park Microcell Center, Nuricell Inc., Sinnae-Technotown, Sangbong-dong, Jungrang-gu, Seoul 131-863, Korea e-mail: scnam@nuricell.com S.-R. Lee Department of Materials Science and Engineering, Korea University, 5ga, Anam-dong, Seongbuk-gu, Seoul 136-701, Korea H. P. Kim College of General Education, Kookmin University, Jeongneung dong, Seongbuk-gu, Seoul 136-702, Korea S. B. Cho Advanced Technology Research Center, Agency for Defense Development, P.O. Box 35, Yuseong, Daejeon 305-600, Korea Introduction With the development of miniaturized electronic devices, thin ﬁlm microbatteries are needed as the power sources for them. Thin ﬁlm electrolytes for all-solid-state lithium batteries are required to have high ionic conductivity, small electronic conductivity and stability with the anodes and cathodes in the range of a working cell potential. Since the Lipon glassy thin ﬁlm was ﬁrst revealed as a promising solid electrolyte by Bates et al. [1–3], some researchers have reported a variation of composition and conductivity as Lipon is deposited by reactive sputtering [4, 5]. Generally, Lipon was reported to exhibit a relatively high ionic conductivity at room temper- ature, high electronic resistivity, no phase change in a wide temperature range and a large stability window (voltage vs. Li/Li + ). It is certain that a small substitution of nitrogen for oxygen in the amorphous Li 3 PO 4 material greatly enhances the Li mobility, due to either the formation of additional cross-linking between phosphate groups or a decrease of the electrostatic energy when P O is exchanged by P N bonds [6]. In spite of the advantages of Lipon as solid electrolyte for thin ﬁlm batteries [7–9], the inﬂuence of deposition pa- rameters on the characteristics of Lipon have not been thor- oughly investigated. Therefore, there is variation in results from group to group, for this reaction is a non-equilibrium synthesis. In addition, a clear analysis of the variation of the properties with process parameters is lacking. It is expected that the electrochemical properties of Lipon thin ﬁlms will depend on process parameters during sput- ter deposition such as sputtering gases, working pressure, power applied to the target and substrate temperature, etc. The objective of the present study is to evaluate the inﬂuence of the working pressure during the sputtering of an Li 3 PO 4 target in nitrogen plasma on the ionic conductivity, stability, composition and structural evolution of Lipon thin ﬁlms. Springer