On the off stoichiometry of cerium oxide thin films deposited by RF sputtering

Chin, Chee Kok; Lin, Ran; Yu, Yang; Wang, C. W.; Lin, E. K.; Tsai, Wan-Lin; Tseng, Tseung‐Yuen

doi:10.1016/0921-4534(96)00125-6

Cited by 12 publications

(11 citation statements)

References 13 publications

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“…As explained previously in Figure 1, greater the oxygen sites on the surface, the greater the tendency to form hydrogen bonds with interfacial water and hence higher the wettability. As seen in Figure 3(a), the O/Ce ratio on a freshly sputterdeposited ceria surface was measured as $3.0, which is similar to observations of Chin et al 51 Indeed, we observed that water spreads on a freshly sputter-deposited ceria surface as shown in Figure 3(c) given the higher-than-stoichiometric O/Ce ratio. However, when this surface was allowed to relax in a UHV environment, the O/Ce ratio approaches the stoichiometric ratio and the surface is rendered hydrophobic (WCA > 90 ) as shown in Figure 3(d).…”

supporting

confidence: 77%

“…There are many factors that could potentially cause a departure from the pristine stoichiometric state of ceria. Chin et al 51 found that freshly sputter-deposited ceria films have an overstoichiometric O/Ce ratio on the surface, reaching as high as 3.3. They attributed this anomaly to cerium vacancies or interstitial excess oxygen on the surface arising from the sputtering process.…”

mentioning

confidence: 99%

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Role of surface oxygen-to-metal ratio on the wettability of rare-earth oxides

Khan

Azimi

Yildiz

et al. 2015

Applied Physics Letters

129

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Hydrophobic surfaces that are robust can have widespread applications in drop-wise condensation, anti-corrosion, and anti-icing. Recently, it was shown that the class of ceramics comprising the lanthanide series rare-earth oxides (REOs) is intrinsically hydrophobic. The unique electronic structure of the rare-earth metal atom inhibits hydrogen bonding with interfacial water molecules resulting in a hydrophobic hydration structure where the surface oxygen atoms are the only hydrogen bonding sites. Hence, the presence of excess surface oxygen can lead to increased hydrogen bonding and thereby reduce hydrophobicity of REOs. Herein, we demonstrate how surface stoichiometry and surface relaxations can impact wetting properties of REOs. Using X-ray Photoelectron Spectroscopy and wetting measurements, we show that freshly sputtered ceria is hydrophilic due to excess surface oxygen (shown to have an O/Ce ratio of ∼3 and a water contact angle of ∼15°), which when relaxed in a clean, ultra-high vacuum environment isolated from airborne contaminants reaches close to stoichiometric O/Ce ratio (∼2.2) and becomes hydrophobic (contact angle of ∼104°). Further, we show that airborne hydrocarbon contaminants do not exclusively impact the wetting properties of REOs, and that relaxed REOs are intrinsically hydrophobic. This study provides insight into the role of surface relaxation on the wettability of REOs.

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supporting

confidence: 77%

mentioning

confidence: 99%

Role of surface oxygen-to-metal ratio on the wettability of rare-earth oxides

Khan

Azimi

Yildiz

et al. 2015

Applied Physics Letters

129

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“…The presence of excess oxygen in sputter-deposited oxide films has been observed before. Chin et al 14 reported the observation by RBS of cerium oxide films with an O/Ce ratio Ͼ2, for films deposited by rf sputtering. For sputterdeposited alumina deviations from stoichiometry were also observed.…”

Section: A Nature Of Trapping Centersmentioning

confidence: 99%

Lithium trapping at excess oxygen in sputter-deposited a-WO3 films

Vink

Boonekamp

Verbeek

et al. 1999

Journal of Applied Physics

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The initial stages of electrochemical intercalation of lithium in sputter-deposited tungsten oxide thin films were studied. The as-deposited films show a substantial irreversible uptake of lithium without an electrochromic effect. This trapping of lithium is associated with the presence of excess oxygen in the film. The experimental results are consistent with a reaction of lithium and interstitial oxygen to form a neutral Li2−Oi complex. Our findings are relevant for the manufacture of electrochromic devices, and the electrochemical titration method used may be applied to probe excess oxygen in other oxidic films as well.

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“…In order to match electronic conductivity of existing working electrode with the prepared electrode, fluorine is selected as a dopant for cadmium oxide [14]. Electron beam evaporation [15], chemical vapor deposition [16], RF sputtering [17] and spray pyrolysis [18,19] are some of the available methods used to deposit TCO thin film. Among the available methods, spray pyrolysis technique was chosen to prepare CdO:F TCO thin film based working electrode because of its cost effectiveness and better reproducibility [20].…”

Section: Introductionmentioning

confidence: 99%