| Autor: |
S.J. Weyers, W.H. Weinberg, Eric W. McFarland, Hermann Nienhaus, B. Gergen |
| Rok vydání: |
2001 |
| Předmět: |
|
| Zdroj: |
Surface Science. 488:123-132 |
| ISSN: |
0039-6028 |
| DOI: |
10.1016/s0039-6028(01)01124-4 |
| Popis: |
Adsorption of ground state nitric oxide and molecular oxygen on Ag at 130 K were observed to produce excited electrons which were detectable as a “chemicurrent” in a large area ultrathin film Ag/Si(1 1 1) Schottky diode sensor. The charge carriers produced at the surface had sufficient lifetimes and energies to reach the Ag/Si interface (6–8 nm) and surmount the Schottky barrier (⩽0.5 eV). The detected current from nitric oxide exposure decreased with increasing coverage from an initial peak intensity of 1×10 −4 e − /incident molecule. A secondary peak (5×10 −5 e − /incident molecule) was observed at an exposure of approximately 22 ML. The signal decayed to the noise floor (∼100 fA) at longer exposures (>40 ML). With molecular oxygen exposure a smaller peak intensity of 1×10 −5 e − /incident molecule was observed, followed by a decay in signal to the noise floor at longer exposures (>10 ML). The signal from nitric oxide is attributed to the superposition of charge carriers produced by nonadiabatic adsorption of NO at 130 K on the Ag surface with carriers generated from the coverage dependent chemisorption of atomic oxygen produced during the formation and decomposition of (NO 2 ) dimers into atomic nitrous oxide. The latter is the cause of the observed secondary peak. The detected current from molecular oxygen exposure on the Ag surface at 130 K is consistent with molecular adsorption generating the detected current. The detection of this “chemicurrent” is direct experimental evidence of nonadiabatic energy transfer during molecular adsorption. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect