ADSORPTION ON ORDERED BINARY ALLOY SURFACES: HYDROGEN ADSORPTION ON THE CLEAN AND CO-COVERED Cu3Pt(111) SURFACE

1996 ◽  
Vol 03 (05n06) ◽  
pp. 1889-1897 ◽  
Author(s):  
C. BECKER ◽  
U. SCHRÖDER ◽  
R. LINKE ◽  
B. SCHIEFFER ◽  
K. WANDELT
Keyword(s):  
Lattice Gas ◽  
Hydrogen Adsorption ◽  
Thermal Desorption Spectroscopy ◽  
Lateral Interaction ◽  
Function Change ◽  
Resolution Electron ◽  
Work Function Change ◽  
Electron Energy Loss ◽  
Adsorption And Dissociation ◽  
Lateral Segregation

The adsorption of hydrogen, as well as the interaction of adsorbed CO and hydrogen, on the Cu 3 Pt (111) surface have been studied using thermal desorption spectroscopy (TDS), high resolution electron energy loss spectroscopy (HREELS) and work function change measurements (ΔΦ). The results show that hydrogen adsorption and dissociation occur via platinum sites. The process proceeds with second order kinetics with respect to the number of platinum sites available. The desorption spectra are successfully simulated using a lattice gas model. From the simulations the desorption and lateral interaction energies are deduced, showing a weak hydrogen-hydrogen repulsion. The interaction of coadsorbed CO and hydrogen has also been investigated. In contrast to the Pt(111) surface where a lateral segregation of the two adsorbed species takes place, the results presented here suggest a mixed overlayer.

Effects of Potassium on the Adsorption and Reactions of Nitric Oxide on Silicon Surface

1988 ◽  
Vol 131 ◽  
Author(s):  
Z. C. Ying ◽  
W. Ho
Keyword(s):  
High Vacuum ◽  
Ultra High Vacuum ◽  
Thermal Heating ◽  
Photon Irradiation ◽  
Structure Changes ◽  
Function Change ◽  
Resolution Electron ◽  
High K ◽  
Work Function Change ◽  
Electron Energy Loss

ABSTRACTThe adsorption, thermoreactions, and photoreactions of NO coadsorbed with K on Si(111)7×7 at 90 K have been studied and compared with the results obtained from the Kfree surface. The experiments were performed under ultra-high vacuum conditions using high resolution electron energy loss spectroscopy, work function change measurements, and mass spectrometry. NO adsorbs both molecularly and dissociatively on the K-free surface. Two molecular N–O stretching modes are observed at 188 and 225 meV. The concentration of these NO molecules on the surface decreases as the K exposure increases and vanishes at high K exposures. A new N–O stretching mode, attributed to adsorption of NO molecules on K clusters, is observed at 157 meV. After thermal heating or photon irradiation, the surface is covered with atomic O and N. The surface is more oxidized in the presence of K. A steady decrease in the photodesorption cross section is observed as the K exposure increases and is attributed to K-induced band structure changes.

Laser and Thermal Induced Reactions of Mo(CO)6, CH3CH2OH, and NO on Si(111)7 × 7

1986 ◽  
Vol 75 ◽  
Author(s):  
Z. Ying ◽  
W. Ho
Keyword(s):  
Gas Phase ◽  
Electron Spectroscopy ◽  
Auger Electron ◽  
Continuous Wave ◽  
Thermal Desorption Spectroscopy ◽  
Continuous Wave Laser ◽  
Thermally Induced ◽  
Resolution Electron ◽  
Wave Laser ◽  
Electron Energy Loss

AbstractLaser induced reactions of Mo(CO)6, CH3CH2OH, and NO adsorbed on Si(111)7 × 7 at 257 and 514 nm were studied and compared with thermally induced reactions under ultrahigh vacuum conditions utilizing laser induced desorption spectroscopy, thermal desorption spectroscopy, high resolution electron energy loss spectroscopy, and Auger electron spectroscopy. By using continuous wave laser irradiation, photolytic effects are clearly distinguished from pyrolytic effects. Mo(CO)6 and CH3CH2OH adsorbed on Si behave similarly as in the gas phase, whereas a substrate-mediated reaction channel is observed for NO adsorbed on Si.

A Field Emission Microscopic Study of Hydrogen Adsorption on a Stepped Tungsten Plane: W(310)

1997 ◽  
Vol 11 (02n03) ◽  
pp. 63-71 ◽  
Author(s):  
D. S. Choi ◽  
S. M. Paik ◽  
J. H. Han ◽  
N. G. Park ◽  
K. S. Kim ◽  
...  
Keyword(s):  
Work Function ◽  
Field Emission ◽  
Hydrogen Adsorption ◽  
Indirect Comparison ◽  
Adsorption Sites ◽  
Function Change ◽  
Field Emission Current ◽  
Average Work ◽  
Work Function Change ◽  
Low Coverage

Using a newly developed Derivative Field Emission Current (DFEC) methods, the heat of desorption and the work-function-change of W(310) plane induced by hydrogen adsorption are measured. The average work function of the W(310) plane increases initially as the hydrogen dose increases for the low coverage region, decreases for the dose higher than about 0.7 Languimir, and saturates at about 4 Languimir. We find the eight hydrogen adsorption sites on the W(310) plane. Three of these sites are on the terrace (100) plane and the hydrogen adsorption on these sites lower the work function. The other three sites are on the step-wall (110) plane raising the work function. Last two sites are probably on the step-edge. The heats of desorption for these sites ranges from 16.6±2.0 kcal/mol for the γ2 state to 32.0±1.0 kcal/mol for the β6 state. An indirect comparison and analysis show that our findings are quite reasonable.

HREELS Studies of Hydrogen Adsorption on Pd(311)

1998 ◽  
Vol 05 (02) ◽  
pp. 473-478 ◽  
Author(s):  
P. Schilbe ◽  
D. Farías ◽  
K. H. Rieder
Keyword(s):  
High Resolution ◽  
Energy Loss ◽  
Electron Energy ◽  
Electron Energy Loss Spectroscopy ◽  
Hydrogen Adsorption ◽  
Adsorption Behavior ◽  
Vibration Modes ◽  
Adsorption Sites ◽  
Resolution Electron ◽  
Electron Energy Loss

The adsorption of hydrogen on Pd(311) at 100 K has been investigated by high resolution electron energy loss spectroscopy (HREELS). The observed vibration energies are similar to former values reported on low index Pd surfaces, which allowed relating the vibration modes with the different adsorption sites on the (311) surface. In contrast to Ni(311) and Rh(311), hydrogen adsorption is found to begin at the fourfold-coordinated instead of the threefold-coordinated sites. The latter sites are occupied only at coverages greater than 0.5 ML. The hydrogen adsorption behavior on Pd(311) seems to be ruled by the possibility of occupying threefold and fourfold sites and by the H–H repulsion.

Sign in / Sign up

Export Citation Format

Share Document