An exploratory study of Li-ion intercalation in atomic layer deposited ͑ALD͒ ZrO 2 has been made. Intercalation parameters have been obtained and the dielectric permittivity as a function of frequency at different intercalation levels has been studied. The ALD-ZrO 2 thin films were polycrystalline with a stable monoclinic polymorph and also nearly stoichiometric. The dielectric response of Li ion intercalated ALD-ZrO 2 reveals complex relaxation processes. The dielectric constant ϱ , shows a strong dependence on the intercalated ion concentration. The explicit variation in dielectric loss, Љ, also suggests different relaxation processes being important at different levels of intercalation. The intercalation probably involves defects in ZrO 2 that give rise to different dipole moments and localized states at different ion concentrations in addition to the expected Li ion-electron pairs. Dielectric properties of thin films have been studied extensively during the past 30 years. 1,2 These studies have covered a wide range of materials and their different phases, including different degrees of doping. 1 Little work has been done, though, on the effects of intercalation on dielectric properties. Intercalation of small ions, e.g., H ϩ , Li ϩ or K ϩ , and their accompanying charge balancing electrons is a process of great importance in, for example, electrochromic devices and thin-film batteries. 3 It is, however, not only of interest in thin film applications; intercalation involves fundamental physics and offers an opportunity to study the effects of e.g., screening of charge carriers on the dielectric response. [4][5][6] In this work, we make an exploratory study of Li-ion intercalation in atomic layer deposited ͑ALD͒ ZrO 2 . The aim is twofold; to study the fundamental physics behind the changes in dielectric response upon intercalation and to further characterize thin film ZrO 2 , an important material for applications in microelectronics e.g., as storage capacitors and in dynamic random access memories, 7 as well as in electrochromics. The ALD-ZrO 2 thin films studied here are polycrystalline with a stable monoclinic polymorph and also nearly stoichiometric. 8 Because the ALD is a low temperature process, impurities are detectable, arising from incomplete surface reactions. The dielectric response of Li ion intercalated ALD-ZrO 2 reveals complex relaxation processes taking place. The intercalation probably involves defects in ZrO 2 that give rise to dipole moments and localized states addition to the expected Li ion-electron pairs. The dielectric response depends on the concentration of intercalated ions and both relaxation peaks and low frequency dispersion is seen. ExperimentalThe ZrO 2 films were grown in an F-120 ALD reactor 9 onto indium-tin-oxide ͑ITO͒-coated substrates at 300°C. ZrCl 4 ͑Aldrich, 99.9%͒ was evaporated inside the reactor at 160°C. Water vapor was led into the reactor from reservoirs held at room temperature. The ZrCl 4 pulse length was 0.4 s, the purge times and H 2 O exposure times were all ...
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