Limits...
Tunable Wetting Property in Growth Mode-Controlled WS 2 Thin Films

View Article: PubMed Central - PubMed

ABSTRACT

We report on a thickness-dependent wetting property of WS2/Al2O3 and WS2/SiO2/Si structures. We prepared WS2 films with gradient thickness by annealing thickness-controlled WO3 films at 800 °C in sulfur atmosphere. Raman spectroscopy measurements showed step-like variation in the thickness of WS2 over substrates several centimeters in dimension. On fresh surfaces, we observed a significant change in the water contact angle depending on film thickness and substrate. Transmission electron microscopy analysis showed that differences in the surface roughness of WS2 films can account for the contrasting wetting properties between WS2/Al2O3 and WS2/SiO2/Si. The thickness dependence of water contact angle persisted for longer than 2 weeks, which demonstrates the stability of these wetting properties when exposed to air contamination.

No MeSH data available.


Related in: MedlinePlus

High-resolution transmission electron microscopy cross section images of WS2 (dWO3 = 1 nm) grown on a Al2O3 and b SiO2 substrates. Insets show corresponding image for the thick WS2 (dWO3 = 8 nm)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5383915&req=5

Fig4: High-resolution transmission electron microscopy cross section images of WS2 (dWO3 = 1 nm) grown on a Al2O3 and b SiO2 substrates. Insets show corresponding image for the thick WS2 (dWO3 = 8 nm)

Mentions: To check the film thickness and crystallinity, we performed cross section TEM analysis for both thin (dWO3 = 1.0 nm) and thick (dWO3 = 8.0 nm) samples for both substrates. Figure 4 shows the TEM images of the thin samples grown on (a) Al2O3 and (b) SiO2/Si substrates. The Al2O3 substrate supported a nearly continuous film with thickness between 1–3 ML, well in agreement with the nominal layer thickness of 1–2 ML, as shown in Fig. 3c. This uniform growth mode corresponds to a nearly linear shift of the A1g peak as a function of dWO3. On the other hand, the film on SiO2/Si substrate had several patches with thicknesses of 1–4 ML and lateral width of ~10 nm. Such nanoscale patches with thickness of a few MLs were consistent with the estimated thickness of 3 ML based on the Raman spectra for dWO3 < 3 nm, as shown in Fig. 3c. Therefore, we understand that very thin WS2 films grow with quite different growth modes during sulfurization, as schematically illustrated in the bottom of Fig. 1.Fig. 4


Tunable Wetting Property in Growth Mode-Controlled WS 2 Thin Films
High-resolution transmission electron microscopy cross section images of WS2 (dWO3 = 1 nm) grown on a Al2O3 and b SiO2 substrates. Insets show corresponding image for the thick WS2 (dWO3 = 8 nm)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5383915&req=5

Fig4: High-resolution transmission electron microscopy cross section images of WS2 (dWO3 = 1 nm) grown on a Al2O3 and b SiO2 substrates. Insets show corresponding image for the thick WS2 (dWO3 = 8 nm)
Mentions: To check the film thickness and crystallinity, we performed cross section TEM analysis for both thin (dWO3 = 1.0 nm) and thick (dWO3 = 8.0 nm) samples for both substrates. Figure 4 shows the TEM images of the thin samples grown on (a) Al2O3 and (b) SiO2/Si substrates. The Al2O3 substrate supported a nearly continuous film with thickness between 1–3 ML, well in agreement with the nominal layer thickness of 1–2 ML, as shown in Fig. 3c. This uniform growth mode corresponds to a nearly linear shift of the A1g peak as a function of dWO3. On the other hand, the film on SiO2/Si substrate had several patches with thicknesses of 1–4 ML and lateral width of ~10 nm. Such nanoscale patches with thickness of a few MLs were consistent with the estimated thickness of 3 ML based on the Raman spectra for dWO3 < 3 nm, as shown in Fig. 3c. Therefore, we understand that very thin WS2 films grow with quite different growth modes during sulfurization, as schematically illustrated in the bottom of Fig. 1.Fig. 4

View Article: PubMed Central - PubMed

ABSTRACT

We report on a thickness-dependent wetting property of WS2/Al2O3 and WS2/SiO2/Si structures. We prepared WS2 films with gradient thickness by annealing thickness-controlled WO3 films at 800&nbsp;&deg;C in sulfur atmosphere. Raman spectroscopy measurements showed step-like variation in the thickness of WS2 over substrates several centimeters in dimension. On fresh surfaces, we observed a significant change in the water contact angle depending on film thickness and substrate. Transmission electron microscopy analysis showed that differences in the surface roughness of WS2 films can account for the contrasting wetting properties between WS2/Al2O3 and WS2/SiO2/Si. The thickness dependence of water contact angle persisted for longer than 2&nbsp;weeks, which demonstrates the stability of these wetting properties when exposed to air contamination.

No MeSH data available.


Related in: MedlinePlus