The ionization of thermal and hyperthermal beams of Na, K, and Cs on Si(111) surfaces

Journal Article · Thu Mar 15 04:00:00 EST 1990 · Journal of Chemical Physics; (USA)

DOI:https://doi.org/10.1063/1.457796· OSTI ID:6993514

Bu, Y; Greene, E F; Stewart, D K ^[1]

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1. Chemistry Department, Brown University, Providence, Rhode Island 02912 (US)

Measurement of the energy dependence of the yields of Na{sup +}, K{sup +}, and Cs{sup +} ions formed when beams of the corresponding alkali atoms M hit a Si(111) surface and of Na{sup +} for Na striking a Pt surface at a temperature {ital T} are those expected for equilibrium for thermal kinetic energies {ital E} of the incident atoms. Above a threshold energy of 0.5--1.0 eV the yields rise rapidly to maxima greater than 0.1 and then remain approximately constant as the energy increases to 100 eV. They are nearly independent of {ital T} in the range 300--1100 K. The results are represented well by a classical model having (1) a rate of electron transfer that varies exponentially with the distance {ital z} of {ital M} from the surface, (2) potentials that slow the incoming atom down as it nears the surface, and (3) energy transfer by elastic two-body collisions with the surface represented as hard cubes, each having the mass of an integral number {ital n} of surface atoms. At {ital z}=5 A the rate on Si for Na and K is 10{sup 12.5{plus minus}0.2} s{sup {minus}1} with {ital n} equal to 3 and 5, respectively, while for Cs it is three times less with {ital n} equal to 20. For Na on Pt it is 10{sup 12.9{plus minus}0.1} s{sup {minus}1} with {ital n} equal to 1.

• DOE Contract Number: FG02-85ER13441
• OSTI ID: 6993514
• Journal Information: Journal of Chemical Physics; (USA), Journal Name: Journal of Chemical Physics; (USA) Journal Issue: 6 Vol. 92:6; ISSN JCPSA; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

656003* -- Condensed Matter Physics-- Interactions between Beams & Condensed Matter-- (1987-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALI METALS
ATOM COLLISIONS
ATOMIC BEAMS
BEAMS
CESIUM
CESIUM IONS
CHARGED PARTICLES
COLLISIONS
ELEMENTS
ENERGY
ENERGY DEPENDENCE
ENERGY RANGE
ENERGY TRANSFER
EV RANGE
IONIZATION
IONS
KINETIC ENERGY
METALS
MILLI EV RANGE
POTASSIUM
POTASSIUM IONS
SEMIMETALS
SILICON
SODIUM
SODIUM IONS
SURFACE IONIZATION
YIELDS