Lithium insertion and electrochromism in polycrystalline molybdenum oxide films

Abstract In this work, molybdenum oxide thin films were deposited by r.f. reactive sputtering of metallic molybdenum target in an Ar+O 2 atmosphere. Thin films with different compositions and crystal structures were obtained by varying the oxygen flow ( φ ). All samples, with the exception of the MoO 2 film, showed an electrochromic behavior, due to the reversible Li + /e − insertion or extraction process. The transmittance change ( λ =632.8 nm), for the best sample, was ∼70%. The film having the best optical behavior is mostly formed by the β-MoO 3 phase. The composition, optical and mechanical properties were determined and analyzed in as-grown and in Li intercalated films. The local order structure was analyzed by X-ray absorption spectroscopy measurements at the Mo L 2,3 -edges. The valence band was studied by Photoelectron Spectroscopy.