Preparation of amorphous lithium ion conductor thin films by pulsed laser deposition Junichi Kawamura a, * , Naoaki Kuwata a , Keisuke Toribami a , Noriko Sata b , Osamu Kamishima a , Takeshi Hattori a a Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aobaku, Sendai, 980-8577, Japan b Graduate School of Engineering, Tohoku University, Sendai, 980-8579, Japan Received in revised form 17 May 2004; accepted 27 May 2004 Abstract Amorphous lithium ion conductor films were prepared by pulsed laser deposition (PLD). The morphology of the films was dependent on the preparation conditions, especially the optical absorbance of the target materials. A good amorphous thin film was obtained for the nominal composition of 0.6(Li 4 SiO 4 )–0.4(Li 3 VO 4 ). The film was characterized through X-ray, FT-IR, Raman, a field emission scanning electron microscope (FE-SEM), an atomic force microscope (AFM) and an inducting coupled plasma (ICP). The ionic conductivity of the film was 10 À7 S/cm at room temperature, which is one order smaller than the previously reported value of a partially crystallized RF- sputtered film. D 2004 Elsevier B.V. All rights reserved. PACS: 66.30.Hs; 68.55.-a; 71.55.Jv; 61.20.Qg Keywords: Thin film lithium battery; Glassy electrolyte; Pulsed laser deposition; Amorphous 1. Introduction Recent developments of small electric devices strongly demand very small power sources with high energy density. For this purpose, a great advance has been achieved in this decade, aiming at all-thin-film solid state batteries [1–7]. One of the key materials for this device is a glassy or amorphous lithium ion conductor, which acts as a solid electrolyte separating positive and negative electrodes. The merit of the use of an amorphous electrolyte instead of a crystalline one is its good contact with the electrodes, ensuring the long life cyclability. For this reason, the amorphous ionic conductors have also been used as a protective layer for the lithium electrode [8], ISFET sensor [4,9], electrochromic displays [10], etc. For the purpose of thin film batteries, different systems were developed starting from Li 2 O–B 2 O 3 glass in the 1980s [11,12], Li 4 SiO 4 –Li 3 PO 4 [1], Li 4 SiO 4 –Li 3 VO 4 [2,3,14,15], etc., and recently, lithium phosphate glass containing nitrogen (LIPON) [6,7]. So far, the solid electrolyte thin films have mainly been prepared through thermal vacuum evaporation [4,12] and RF-sputtering [1,2,6,7,13–15]. The pulsed laser deposition (PLD) has been known as an excellent technique to produce good quality thin films and used for preparing positive electrodes LiCoO 2 [16], LiMn 2 O 4 [17] and tin- based negative electrodes [18]. The merit of the PLD method is (i) conserving the stoichiometry of the target material, (ii) small contamination from the chamber pollution, (iii) only a small target is used, etc. However, PLD has been used mainly for electrode materials and not for electrolytes, probably because the growth mechanism is very complicated [19,20], which causes variation of the film quality depending on the preparation procedure. In this paper, some results will be reported on the preparation of amorphous lithium conductor thin films through the PLD technique. Only few materials could be fabricated 0167-2738/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.ssi.2004.05.034 * Corresponding author. Tel./fax: +81 22 217 5344. E-mail address: kawajun@tagen.tohoku.ac.jp (J. Kawamura). Solid State Ionics 175 (2004) 273 – 276 www.elsevier.com/locate/ssi