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Hydrogen on WO3(001)
A382 80
Surface Sctence 111 (1981) 80-86 North-Holland Publishing Company
HYDROGEN
ON W03(O01)
R.D BRINGANS,H HOCHST andH.R SHANKS * ~llax-Plat~ck-It~st~~ t fur I.estkorperj.orschurlg, Repu hhc of German) Recerved
27 March
1981, accepted
Hemwhergstr
for pubhcdtron
I, D- 7000 Stuttgart
18 June
80, Federal
1981
Ultravrolet photoemission measurements of the (001) surface of WOs show that after exposure to atomrc hydrogen new states appear in the energy gap regron at 2 3 and 0 9 eV below the Fermi energy. A pedk at 2 2 eV was also produced by hydrogen Ion bombardment To investigate whether these surface effects were due to the formatron of hydrogen tungsten bronze H,WOs, comparison was made with spectra from the electronically snntlar sodium bronze. The form of the spectra were drfferent both in the valence band and energy gap regrons indicating that hydrogen adsorptron or loss of oxygen from the surface rather than formatron of H,WOs 1s the maJor effect
Surface Science 111 (19X1) 87 101 North-Holland Pubhshmg Company
Hz0 INTERACTION
WITH CLEAN AND OXYGEN PRECOVERED
C. BENNDORF, C. NOBL, Instltut fur Physlkahsche West Germail> Received
16 March
87
M. ROSENBERG
Chenue.
1981, accepted
and
L~ruversltat Hamburg, for pubhcatron
Ni( 110)
F THIEME Laufgraben
16 June
-74, D-2000 Hamburg
13.
1981
The mteractron of water vapour with clean as well as with oxygen precovered Nr(110) surfaces was studied at 150 and 273 K, usmg UPS, A@, TDS, and E.LS The He(l) (He(H)) excited UPS mdrcate a molecular adsorption of Ha 0 on Nr(110) at 150 K, showing three water-mduced peaks at 6.5, 9.5 and 12.2 eV below EF (6 8, 9.4 and 12.7 eV below EF). The dramatic decrease of the Ni d-band intensity at hrgher exposures, as well as the course of the work function change, demonstrates the formation of HZ0 multrlayers (ice). The observed energy shift of all water-induced UPS peaks relative to the Fermi level (timax = 1.5 eV at 200 L) wrth increasing coverage is related to extra-atomic relaxatron effects The activation energies of desorption were estimated as 14 9 and 17 3 kcal/mole From the ELS measurements we conclude a great sensitivity of Hz0 for electron beam induced drssocratton. At 273 K water adsorbs on Ni(ll0) only in the presence of oxygen, with two peaks at 5.7 and 9.3 eV below _!?F (He(II)), bemg interpreted as due to hydroxyl species (OH)6- on the surface A kinetic model for the Ha0 adsorption on oxygen precovered Ni(ll0) surfaces is proposed, and verified by a simple Monte Carlo calculatron leadmg to the same dependence of the maximum amount of adsorbed Hz0 on the oxygen precoverage as revealed by work function measurements. On heatmg, some of the (OH)6- recombines and desorbs as Ha0 at -320 K, leavmg behmd an oxygen covered Ni surface.
Surface Sctence 111 (1981) 80-86 North-Holland Publishing Company
HYDROGEN
ON W03(O01)
R.D BRINGANS,H HOCHST andH.R SHANKS * ~llax-Plat~ck-It~st~~ t fur I.estkorperj.orschurlg, Repu hhc of German) Recerved
27 March
1981, accepted
Hemwhergstr
for pubhcdtron
I, D- 7000 Stuttgart
18 June
80, Federal
1981
Ultravrolet photoemission measurements of the (001) surface of WOs show that after exposure to atomrc hydrogen new states appear in the energy gap regron at 2 3 and 0 9 eV below the Fermi energy. A pedk at 2 2 eV was also produced by hydrogen Ion bombardment To investigate whether these surface effects were due to the formatron of hydrogen tungsten bronze H,WOs, comparison was made with spectra from the electronically snntlar sodium bronze. The form of the spectra were drfferent both in the valence band and energy gap regrons indicating that hydrogen adsorptron or loss of oxygen from the surface rather than formatron of H,WOs 1s the maJor effect
Surface Science 111 (19X1) 87 101 North-Holland Pubhshmg Company
Hz0 INTERACTION
WITH CLEAN AND OXYGEN PRECOVERED
C. BENNDORF, C. NOBL, Instltut fur Physlkahsche West Germail> Received
16 March
87
M. ROSENBERG
Chenue.
1981, accepted
and
L~ruversltat Hamburg, for pubhcatron
Ni( 110)
F THIEME Laufgraben
16 June
-74, D-2000 Hamburg
13.
1981
The mteractron of water vapour with clean as well as with oxygen precovered Nr(110) surfaces was studied at 150 and 273 K, usmg UPS, A@, TDS, and E.LS The He(l) (He(H)) excited UPS mdrcate a molecular adsorption of Ha 0 on Nr(110) at 150 K, showing three water-mduced peaks at 6.5, 9.5 and 12.2 eV below EF (6 8, 9.4 and 12.7 eV below EF). The dramatic decrease of the Ni d-band intensity at hrgher exposures, as well as the course of the work function change, demonstrates the formation of HZ0 multrlayers (ice). The observed energy shift of all water-induced UPS peaks relative to the Fermi level (timax = 1.5 eV at 200 L) wrth increasing coverage is related to extra-atomic relaxatron effects The activation energies of desorption were estimated as 14 9 and 17 3 kcal/mole From the ELS measurements we conclude a great sensitivity of Hz0 for electron beam induced drssocratton. At 273 K water adsorbs on Ni(ll0) only in the presence of oxygen, with two peaks at 5.7 and 9.3 eV below _!?F (He(II)), bemg interpreted as due to hydroxyl species (OH)6- on the surface A kinetic model for the Ha0 adsorption on oxygen precovered Ni(ll0) surfaces is proposed, and verified by a simple Monte Carlo calculatron leadmg to the same dependence of the maximum amount of adsorbed Hz0 on the oxygen precoverage as revealed by work function measurements. On heatmg, some of the (OH)6- recombines and desorbs as Ha0 at -320 K, leavmg behmd an oxygen covered Ni surface.