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. 2019 Feb 22;9(12):6482-6493.
doi: 10.1039/c8ra08494g.

Crystal phase content-dependent functionality of dual phase SnO2-WO3 nanocomposite films via cosputtering crystal growth

Yuan-Chang Liang  1 , Yu Chao  1
Affiliations

Crystal phase content-dependent functionality of dual phase SnO2-WO3 nanocomposite films via cosputtering crystal growth

Yuan-Chang Liang et al. RSC Adv. .

Abstract

In this study, crystalline SnO2-WO3 nanocomposite thin films were grown through radio-frequency cosputtering of metallic Sn and ceramic WO3 targets. The W content in the SnO2 matrix was varied from 5.4 at% to 12.3 at% by changing the WO3 sputtering power during thin-film growth. Structural analyses showed that increased WO3 phase content in the nanocomposite films reduced the degree of crystallization of the SnO2 matrix. Moreover, the size of the composite films' surface crystallites increased with WO3 phase content, and the large surface crystallites were composed of numerous nanograins. Addition of WO3 crystals to the SnO2 matrix to form a composite film improved its light harvesting ability. The SnO2-WO3 nanocomposite films exhibited improved photodegradation ability for Rhodamine B dyes compared with their individual constituents (i.e., SnO2 and WO3 thin films), which is attributable to the suitable type II band alignment between the SnO2 and WO3. Moreover, an optimal WO3 phase content (W content: 5.4 at%) in the SnO2 matrix substantially enhanced the ethanol gas-sensing response of the SnO2 thin film. This suggested that the heterojunctions at the SnO2/WO3 interface regions in the nanocomposite film considerably affected its ethanol gas-sensing behavior.

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Conflict of interest statement

There are no conflicts to declare.

Figures

Fig. 1
Fig. 1. (a) XRD pattern of the SnO2 film and XRD patterns of SnO2–WO3 composite films prepared at various WO3 sputtering powers: (b) 35 W, (c) 50 W, (d) 65 W.
Fig. 2
Fig. 2. (a) SEM image of the SnO2 film. SEM images of SnO2–WO3 composite films prepared at various WO3 sputtering powers: (b) 35 W, (c) 50 W, (d) 65 W.
Fig. 3
Fig. 3. TEM analyses of the SnO2–WO3 composite film prepared at the WO3 sputtering power of 35 W: (a) low-magnification TEM image. (b) SAED pattern. (c) High-magnification image. The HRTEM images taken from the local regions of the film are shown in the insets. (d) EDS spectra of Sn, W, and O elements taken from the film.
Fig. 4
Fig. 4. TEM analyses of the SnO2–WO3 composite film prepared at the WO3 sputtering power of 65 W: (a) low-magnification TEM image. (b) SAED pattern. (c) High-magnification image. The HRTEM images taken from the local regions of the film are shown in the insets. (d) EDS spectra of Sn, W, and O elements taken from the film.
Fig. 5
Fig. 5. (a) and (b) are water contact angle results on the SnO2 and WO3 films, respectively. (c), (d), and (e) are water contact angle results on the SnO2–WO3 composite films prepared at the WO3 sputtering powers of 35, 50, and 65 W, respectively.
Fig. 6
Fig. 6. (a) UV-Vis absorbance spectra of the SnO2, WO3, and various SnO2–WO3 films. (b) Tauc plot of the SnO2 film. (c) Tauc plot of the WO3 film.
Fig. 7
Fig. 7. The absorbance spectra of the RhB solution containing various thin-film samples under different irradiation durations: (a) 30 min. (b) 60 min. (c) 90 min. (d) 120 min. (e) Percentage photodegradation vs. irradiation duration of the RhB solution containing various thin-film samples. (f) Illustration of photodegradation mechanism for the SnO2–WO3 composite film to RhB dyes. (g) Recycled performances in the presence of the SnO2–WO3 film prepared at 65 W sputtering power of WO3 for photodegrading RhB dyes.
Fig. 8
Fig. 8. Temperature-dependent 100 ppm ethanol gas-sensing responses of the SnO2–WO3 composite film prepared at 35 W sputtering power of WO3.
Fig. 9
Fig. 9. (a) and (b) are ethanol gas-sensing response curves of the SnO2 and WO3 films, respectively. (c), (d), and (e) are gas-sensing response curves of the SnO2–WO3 films prepared at WO3 sputtering powers of 35, 50, and 65 W, respectively. (f) Gas-sensing response values vs. ethanol vapor concentrations for various thin films. (g) Cyclic gas-sensing response curves for the SnO2–WO3 film prepared at 35 W sputtering power of WO3 on exposure to 750 ppm ethanol vapor. (h) Gas sensing selectivity histogram of the SnO2–WO3 composite film prepared at 35 W sputtering power of WO3 on exposure to 5 ppm NO2 and 100 ppm of H2 and NH3.
Fig. 10
Fig. 10. Schematics of ethanol gas-sensing mechanisms for the SnO2 and SnO2–WO3 films.
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