Water adsorption, solvation and deliquescence of alkali halide thin films on SiO2 studied by ambient pressure X-ray photoelectron spectroscopy

Journal Article · Wed Mar 31 04:00:00 EDT 2010 · Journal Physical Chemistry C

OSTI ID:1007496

Arima, Kenta; Jiang, Peng; Deng, Xingyi; Bluhm, Henrik; Salmeron, Miquel

The adsorption of water on KBr thin films evaporated onto SiO2 was investigated as a function of relative humidity (RH) by ambient pressure X-ray photoelectron spectroscopy. At 30percent RH adsorbed water reaches a coverage of approximately one monolayer. As the humidity continues to increase, the coverage of water remains constant or increases very slowly until 60percent RH, followed by a rapid increase up to 100percent RH. At low RH a significant number of the Br atoms are lost due to irradiation damage. With increasing humidity solvation increases ion mobility and gives rise to a partial recovery of the Br/K ratio. Above 60percent RH the increase of the Br/K ratio accelerates. Above the deliquescence point (85percent RH), the thickness of the water layer continues to increase and reaches more than three layers near saturation. The enhancement of the Br/K ratio at this stage is roughly a factor 2.3 on a 0.5 nm KBr film, indicating a strong preferential segregation of Br ions to the surface of the thin saline solution on SiO2.

• Research Organization: Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
• Sponsoring Organization: Chemical Sciences Division; Materials Sciences Division
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 1007496
• Report Number(s): LBNL-4302E
• Journal Information: Journal Physical Chemistry C, Journal Name: Journal Physical Chemistry C
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ADSORPTION
ATOMS
HALIDES
HUMIDITY
Hydration
Ion segregation
saline solution aerosol
ION MOBILITY
IRRADIATION
SATURATION
SEGREGATION
SOLVATION
THICKNESS
THIN FILMS
WATER
X-RAY PHOTOELECTRON SPECTROSCOPY