Chemical composition and crystal structure of tungsten oxide films

Abstract

The most typical results of studies on the chemical and phase compositions of the tungsten oxide films synthesized by different chemical and physical methods, including the films that have undergone addi tional thermal treatment in vacuum and in the air, are reviewed.

Enhancing the Spectroelectrochemical Performance of WO3 Films by Use of Structure-Directing Agents during Film Growth

“…For WO3|mp, however, the mass loss of the precursor is similar to the one of the precursor without any additives confirming that residuals The amorphous character of the WO 3 thin films annealed at temperatures T ≤ 300 • C was confirmed by Raman spectroscopy. In the Raman spectra (Figure S3) measured for the films prepared without and with PEG at T ≤ 300 • C a broad peak at 770 cm −1 was observed caused by vibrations of W 6+ -O bonds [12,45] while a relatively sharp peak at 950 cm −1 reflects the stretching of W 6+ =O bonds characteristic for amorphous WO 3 [12,45,46]. For the WO 3| µp600 thin film, another broad peak at 220 cm −1 was noticed which might correspond to the bridging of O-W 4+ -O bonds and indicates the presence of W 4+ ions and oxygen vacancies within the films [12,45].…”

“…In the Raman spectra (Figure S3) measured for the films prepared without and with PEG at T ≤ 300 • C a broad peak at 770 cm −1 was observed caused by vibrations of W 6+ -O bonds [12,45] while a relatively sharp peak at 950 cm −1 reflects the stretching of W 6+ =O bonds characteristic for amorphous WO 3 [12,45,46]. For the WO 3| µp600 thin film, another broad peak at 220 cm −1 was noticed which might correspond to the bridging of O-W 4+ -O bonds and indicates the presence of W 4+ ions and oxygen vacancies within the films [12,45].…”

“…Therefore, a peroxotungstic acid-based precursor solution was used with addition of PEG 400, PEG 600 (for a formation of micropores [37]) or the diblock copolymer PIB 50 -b-PEO 45 that had been successfully used for the preparation of mesoporous titanium oxide [35,38]. To obtain WO 3 thin films with interconnected mesopores, a mixture of PEG 600 and PIB 50 -b-PEO 45 was established. The structural, optical, electrochemical and spectroelectrochemical properties of the WO 3 thin films using these approaches were characterized and compared to compact films prepared without additives.…”

Low‐Voltage Electrochemical LixWO3 Synapses with Temporal Dynamics for Spiking Neural Networks

“…Two strongest peaks in Raman spectra of WO 3 film are located at ≈715 and ≈804 cm −1 , corresponding to the asymmetric and symmetric stretching vibrations of W 6+ O bonds, whereas the peak at ≈278 cm −1 is due to the bridging OWO bonds. [ 59,60 ] The intercalation of Li ions induces a larger lattice distortion, forcing the crystal structure to become more symmetric, which leads to the gradual diminishing of the peak at 715 cm −1 as well as a blue shift of the peak from ≈804 to ≈806 cm −1 , resulting from the slightly decreased lattice parameters of Li x WO 3 bronzes. [ 44 ]…”

Microstructure and optical properties of W/W‐WxN/WOx multilayer metal‐dielectric solar selective absorbing coating

“…17 The XPS analysis results show the presence of W, WO 3 and W 2 O 5 structures, as well as W x N structures, in the absorber layer. WO 3 is stable in the temperature interval of 200-400 C in a hexagonal phase structure, 24,25 and WO 2 and WO 3 have high melting points and good hightemperature oxidation resistance, 26 as well as low Gibbs free energy, 27 and have more stable physical and chemical properties at And the peaks in the WO x antireflective layer's W 4f energy spectrum (Figure 4D) correspond to the existence of W 4+ (33.1 and 33.8 eV), W 6+ (35.2 and 35.3 eV), and W 5+ (38.9 eV) oxidation states, respectively.…”