Structure and composition of sputter-deposited nickel-tungsten oxide films

Abstract

Films of mixed nickel-tungsten oxide, denoted Ni x W 1-x oxide, were prepared by reactive DC magnetron co-sputtering from metallic targets and were characterized by Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy, X-ray diffractometry and Raman spectroscopy. A consistent picture of the structure and composition emerged, and at x < 0.50 the films comprised a mixture of amorphous WO 3 and nanosized NiWO 4 , at x = 0.50 the nanosized NiWO 4 phase was dominating, and at x > 0.50 the films contained nanosized NiO and NiWO 4 , and possibly also WO 3 .

Cyclic voltammetry on sputter-deposited films of electrochromic Ni oxide: Power-law decay of the charge density exchange

“…The present paper lays a foundation for a comprehensive investigation of electrochromism in the Ni-Ir oxide system-with a scope that is similar to the one in our recent work on the electrochromism in the full Ni-W system [23,25,[71][72][73]-but is of interest also in its own right. Data on pure Ir oxide immersed in propionic acid, potassium hydroxide (KOH), and lithium perchlorate in propylene carbonate (Li-PC) were presented recently [74].…”

Ellipsometrically determined optical properties of nickel-containing tungsten oxide thin films: Nanostructure inferred from effective medium theory

“…Our earlier work 17 showed that Ni x W 1Àx oxide films with 0 x 0.5 could be described as nanocomposites comprised WO 3 and NiWO 4 . We now consider whether the optical data presented above can be understood from this premise by turning to effective medium theory.…”

“…Further details of thin film deposition and of structural and compositional characterization can be found elsewhere. 17 Surface morphology and roughness, which are relevant for the ellipsometric analysis, were recorded by atomic force microscopy (AFM) using a Veeco Dimension 3100 instrument in tapping mode in air. We used a tip with a radius of 12 nm, which gave a lateral resolution of roughly 30 nm.…”

“…13 We have therefore embarked on a comprehensive investigation of the full Ni x W 1Àx oxide system, with 0 x 1, and previously reported on the compatibility of these oxides with different electrolytes, 14 optical properties as determined by spectroscopic ellipsometry, 15,16 as well as nanostructures and compositions recorded by Raman spectroscopy, x-ray photoelectron spectroscopy, x-ray diffractometry, and Rutherford backscattering spectrometry. 17 Furthermore, we have studied the electrochromism for films with 0 x 0.6. 6 In the present paper, we determine the optical properties of Ni x W 1Àx oxide films by spectroscopic ellipsometry, interpret these properties within effective medium theory, and show that the data are fully consistent with the nanostructural information reported before, thereby lending further credence to a two-phase model with WO 3 and NiWO 4 as the discrete structural entities for 0 x 0.5.…”

UV-VUV synchrotron radiation spectroscopy of NiWO4

“…Among them, nickel tungstate (NiWO 4 ) finds applications in catalysis [11][12][13][14], as humidity [15] and gas [16] sensor, a photoanode in photovoltaic electrochemical cell [17], a pigment [18] and in microwave [19] and electrochromic [20,21] devices. These applications are tightly connected to its electronic structure being scarcely studied in the past.…”