Structural and Electrochemical Properties of ZrO₂·H_x Thin Films Deposited by Reactive Sputtering in Hydrogen Atmosphere as Solid Electrolytes

Abstract

The feasibility of applying ZrO 2 . H x thin films as solid electrolytes in solid-state ionic energy systems, such as solid oxide fuel cells and supercapacitors was studied. ZrO 2 . H x thin films were deposited on Pt/Ti/SiO 2 /Si substrates by radio-frequency reactive sputtering with various hydrogen volume fractions in reactive gas. With a variation in hydrogen volume fraction, the surface roughness of the as-deposited films increased. In addition, the structure of the as-deposited films grew in the [111] direction with an increase in hydrogen volume fraction. By Rutherford backscattering spectrometry (RBS) and secondary ion mass spectrometry (SIMS) studies, the Zr/O ratio and hydrogen distribution were evaluated. On the basis of a sample structure of Pt/ZrO 2 . H x /Pt/Ti/SiO 2 /Si for measuring an electrochemical property, an impedance measurement conducted at room temperature revealed an ionic conductivity of 1:67 Â 10 À6 S/cm, suggesting that ZrO 2 . H x thin films can possibly be used as solid oxide thin film electrolytes in all solid-state ionics power devices requiring a hydrogen conducting electrolyte.

Preparation of an Inorganic All-Solid-State Electrochromic Device with Excellent Open-Circuit Memory

“…21 At around 160 °C, the conductivity attains a value of 10 −7 S cm −1 , which fully meets the service conditions of inorganic solid ECDs. 22 However, when the temperature is decreased to 25 °C, the conductivity of the sample has been unable to be measured from the Nersten curve (Figure S2, Supporting Information), indicating that the room temperature conductivity of this material is very poor. Therefore, this type of material has the following features: at room temperature, this material is nonconductive, but as the temperature increases, the conductivity increases.…”

Effect of Heat Treatment on Ion Conductivity of Hydrated ZrO2 Thin Films Prepared by Reactive Sputtering Using H2O Gas

“…14) are thought to be caused by the lower H 2 O content in our films, as described above. The ion conductivity was maintained high even after heat treatment at 200 C, however, it began to decrease after heat treatment above 250 C. Even though some of H 2 O molecules are desorbed from the film during heat treatment, H 2 O molecules are absorbed by the films again at room temperature, owing to the low film density and porous structure of the ZrO 2…”

“…12) Ion conductivities of hydrated ZrO 2 have been investigated, and England et al 13) reported an ion conductivity of 2 Â 10 À5 S/cm at room temperature for ZrO 2Á 1.75H 2 O powder prepared by a sol-gel technique. Kim et al 14) reported a room-temperature ion conductivity of 1:67 Â 10 À6 S/cm for ZrO 2Á H x thin films with x ¼ 1:70, deposited by reactive sputtering in Ar þ H 2 þ O 2 atmosphere. Furthermore, ZrO 2 solid electrolyte thin films have been successfully applied to all-solid-state electrochromic devices 14,15) and switchable mirrors.…”

“…Kim et al 14) reported a room-temperature ion conductivity of 1:67 Â 10 À6 S/cm for ZrO 2Á H x thin films with x ¼ 1:70, deposited by reactive sputtering in Ar þ H 2 þ O 2 atmosphere. Furthermore, ZrO 2 solid electrolyte thin films have been successfully applied to all-solid-state electrochromic devices 14,15) and switchable mirrors. 16,17) In consideration of the merits of the sputtering method and safety from the explosion of hydrogen gas, as reported in a previous paper, 18) we prepared hydrated Ta 2 O 5 thin films by reactive sputtering in H 2 O atmosphere.…”

Formation of hydrated yttrium oxide and titanium oxide thin films by reactive sputtering in H2O atmosphere and their electrical properties

“…[1][2][3][4][5][6] Hydrogen-containing tantalum oxide and zirconium oxide are considered to be candidate proton conducting solid electrolytes, and some of their previously reported data are shown in Table I. [7][8][9][10][11][12] Although the proton conductivities of the sputtered films were relatively lower than those of the films prepared by ion plating and sol-gel techniques, the sputtering technique is considered to be suitable for forming large-area thin films with uniform thickness and quality. Our group has developed a new reactive sputtering technique using H 2 O as a reactive gas and applied the technique to deposit hydrated Ta 2 O 5 and ZrO 2 thin films.…”