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Ni(100) interface
A414 Surface Science 189/190 (1987) 405-410 North-Holland, Amsterdam
405
WETYING IN N A R R O W GAPS A N D CAPILLARIES: T E M P E R A T U R E AND SURFACE-PRESSURE-INDUCED WETFING TRANSITIONS Ch. F A T F I N G E R , G. T O G N I and W. L U K O S Z Optics Laboratory, Swiss t'~,deral Institute of Technolo~', 8093 Ziirich, Switzerland Received 14 May 1987; accepted for publication 26 May 1987 We describe a new optical method for the investigation of wetting films on glass surfaces. Fluorescent dye molecules are used as tracers for one of the two fluid phases 1 or 2; their fluorescence in the vicinity of the glass interface is excited by an evanescent wave with a small depth of penetration z0, ~ = 8 0 ran. For the system 2,6-1utidine+water in contact with glass surfaces we observed the transition from wetting to non-wetting as a function of temperature T in wide gaps, and found wetting temperatures T,~ = 4 1 ° C on Schott LASFN15 glass, and T,~ = 39 ° C on BK7 glass, respectively. We predict a surface-pressure-induced wetting transition to occur in this system in narrow gaps and capillaries, i.e. at constant temperature T, a transition from wetting to non-wetting with decreasing gap width d~. This transition is caused by the surface pressure TI.2/R, where R = do~2 is the radius of curvature of the interface between phases 1 and 2, and T1.2 is the surface tension. At constant gap width d~, the wetting temperature T,, will depend on do.
Surface Science 189/190 (1987l 411-419 North-Holland. Amsterdam
411
CRYSTAL-FACE SPECIFIC E L E C T R O C H E M I C A L EFFECTS ON CADMIUM SULPHIDE A.S. FEINER, A.J. McEVOY and P.P. I N F E L T A lnstitut de Chimie Physique, Ecole Polytechnique Fdddrale de Lausanne, 1015 Lausanne, Switzerland Received 30 March 1987; accepted for publication 15 April 1987 The energetics of a semiconductor/electrolyte interface are conditioned by the crystallography of the surface presented to the electrolyte. The effect is particularly significant for anisotropic single crystal compound semiconductor photoelectrochemistry. The relevant interface parameters for single crystal n-type cadmium sulphide photoanodes in contact with electrolytes are investigated. The significant influence of dissolved oxygen in the electrolyte is noted.
420
Surface Science 189/190 11987) 420-425 North-Holland, A m s t e r d a m
A D S O R P T I O N OF H 2 S A N D H 2 0 O N A CYLINDRICAL Ge S A M P L E H.J. K U H R and W. R A N K E Fritz-Haber-lnstitut der Max-Planck-Gesellschaft, Farada.vweg 4-O, D-IO00 Berlin 33, Germany Received 4 March 1987: accepted for publication 16 April 1987 The orientation dependence of H2S and H 2 0 adsorption on a cylindrical Ge crystal was studied in the range (110)-(111 )-(113)-(001). On (001), the coverage saturates at 0.5 ML for both
405
WETYING IN N A R R O W GAPS A N D CAPILLARIES: T E M P E R A T U R E AND SURFACE-PRESSURE-INDUCED WETFING TRANSITIONS Ch. F A T F I N G E R , G. T O G N I and W. L U K O S Z Optics Laboratory, Swiss t'~,deral Institute of Technolo~', 8093 Ziirich, Switzerland Received 14 May 1987; accepted for publication 26 May 1987 We describe a new optical method for the investigation of wetting films on glass surfaces. Fluorescent dye molecules are used as tracers for one of the two fluid phases 1 or 2; their fluorescence in the vicinity of the glass interface is excited by an evanescent wave with a small depth of penetration z0, ~ = 8 0 ran. For the system 2,6-1utidine+water in contact with glass surfaces we observed the transition from wetting to non-wetting as a function of temperature T in wide gaps, and found wetting temperatures T,~ = 4 1 ° C on Schott LASFN15 glass, and T,~ = 39 ° C on BK7 glass, respectively. We predict a surface-pressure-induced wetting transition to occur in this system in narrow gaps and capillaries, i.e. at constant temperature T, a transition from wetting to non-wetting with decreasing gap width d~. This transition is caused by the surface pressure TI.2/R, where R = do~2 is the radius of curvature of the interface between phases 1 and 2, and T1.2 is the surface tension. At constant gap width d~, the wetting temperature T,, will depend on do.
Surface Science 189/190 (1987l 411-419 North-Holland. Amsterdam
411
CRYSTAL-FACE SPECIFIC E L E C T R O C H E M I C A L EFFECTS ON CADMIUM SULPHIDE A.S. FEINER, A.J. McEVOY and P.P. I N F E L T A lnstitut de Chimie Physique, Ecole Polytechnique Fdddrale de Lausanne, 1015 Lausanne, Switzerland Received 30 March 1987; accepted for publication 15 April 1987 The energetics of a semiconductor/electrolyte interface are conditioned by the crystallography of the surface presented to the electrolyte. The effect is particularly significant for anisotropic single crystal compound semiconductor photoelectrochemistry. The relevant interface parameters for single crystal n-type cadmium sulphide photoanodes in contact with electrolytes are investigated. The significant influence of dissolved oxygen in the electrolyte is noted.
420
Surface Science 189/190 11987) 420-425 North-Holland, A m s t e r d a m
A D S O R P T I O N OF H 2 S A N D H 2 0 O N A CYLINDRICAL Ge S A M P L E H.J. K U H R and W. R A N K E Fritz-Haber-lnstitut der Max-Planck-Gesellschaft, Farada.vweg 4-O, D-IO00 Berlin 33, Germany Received 4 March 1987: accepted for publication 16 April 1987 The orientation dependence of H2S and H 2 0 adsorption on a cylindrical Ge crystal was studied in the range (110)-(111 )-(113)-(001). On (001), the coverage saturates at 0.5 ML for both