Controlling the optical properties of sputtered-deposited LixV2O5 films

Abstract

This study examines the influence of lithium intercalation on the optical properties of vanadium pentoxide films. The films with a thickness between 400 and 1000 nm were prepared by DC magnetron sputter deposition. Cyclic voltammetry and chronopotentiometry were used to set a well defined lithiation state of the LixV2O5 films between x = 0 and x = 1. The optical properties of these films were measured by optical reflectometry in the wavelength range between 500 and 1700 nm. From the reflectance data, the refractive index and the extinction coefficient of the films were finally calculated as a function of the wavelength using Cauchy's dispersion model. The results confirm that the optical behavior of LixV2O5 films varies significantly upon lithium insertion. It is demonstrated that the changes produced in the optical properties are completely reversible within the limits of permanent structure changes.

Electrochemical Proton Intercalation in Vanadium Pentoxide Thin Films and its Electrochromic Behavior in the near‐IR Region

“…The reflectivity and therefore the n and k values of the material can be influenced systematically with proton insertion. The behavior of H x V 2 O 5 is comparable with Li x V 2 O 5 [18] although the absolute change of the optical constants, especially the absorption coefficient k , is smaller with proton intercalation than with lithiation. However, one advantage over Li x V 2 O 5 is that it is easier to handle in non‐inert environments, as there is no need for moisture‐sensitive materials like metallic lithium.…”

“…For comparison with literature values of e. g. lithiated V 2 O 5 , it is helpful to determine~n/~x and~k/~x at a distinguished wavelength. According to [18]~n /~x is À 1 and~k/…”

“…For comparison with literature values of e. g. lithiated V 2 O 5 , it is helpful to determine ~n/ ~x and ~k/ ~x at a distinguished wavelength. According to [18] ~n/ ~x is À 1 and ~k/ ~x is 1.43 for Li x V 2 O 5 at a wavelength of 1550 nm. For our investigated system H x V 2 O 5 ~n/ ~x is round about À 0.93 and ~k/ ~x round about 0.15 at the same wavelength.…”

“…There, the electrochromic effect has only been studied with lithium intercalation and in the visible range of the electromagnetic spectrum. In previous works we examined the electrochromic properties of lithiated V 2 O 5 in the near‐infrared (near‐IR) region [18] . Nevertheless, there is only few information available regarding insertion of protons.…”

Recent advances in vanadium pentoxide (V2O5) towards related applications in chromogenics and beyond: fundamentals, progress, and perspectives

“…(where I is a sufficiently low applied current, and t is the time necessary to apply a current to obtain the lithium concentration). 212 The lithium concentration x in Li x V 2 O 5 is characteristic of the film color. For example, when x = 0.5 and 1, green and blue colors are observed, as shown in eqn ( 15) and ( 16), respectively.…”