Slow positrons in metal single crystals. I. Positronium formation at Ag(100), Ag(111), and Cu(111) surfaces

Journal Article · Tue Jul 01 04:00:00 EDT 1980 · Phys. Rev., B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.22.99· OSTI ID:5256299

Lynn, K G; Welch, D O

Monoenergetic positrons, with an incident energy of 0 --5 keV, were focused onto Ag(100), Ag(111), and Cu(111) surfaces with submonolayer contamination, and positronium formation was studied as a function of sample temperature from 300 to 1200 K. The data were fitted with a simple positron diffusion model including surface and vacancy trapping, assuming that positronium is formed only at the surface. The formation of part of the positronium fraction is found to be a temperature-activated process which is identified as detrapping from a surface state, and an estimate of the binding energy in this trap is deduced. The diffusion length is found to be only slightly temperature dependent between room temperature and the onset of vacancy trapping. At the higher sample temperatures positron trapping at thermally generated vacancies is observed by the decrease in the positron diffusion length at the higher incident voltages. A vacancy formation energy is extracted from the data and is generally found to be lower than the values obtained from bulk measurements.

• Research Organization: Brookhaven National Laboratory, Upton, New York 11973
• OSTI ID: 5256299
• Journal Information: Phys. Rev., B: Condens. Matter; (United States), Journal Name: Phys. Rev., B: Condens. Matter; (United States) Vol. 22:1; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
640303 -- Atomic
Molecular & Chemical Physics-- Positronium
Muonium
& Muonic & Mesic Atoms & Molecules
74 ATOMIC AND MOLECULAR PHYSICS
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
BINDING ENERGY
CONTAMINATION
COPPER
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
CRYSTALS
DIFFUSION LENGTH
ELEMENTARY PARTICLES
ELEMENTS
ENERGY
FERMIONS
FORMATION FREE ENERGY
FREE ENERGY
LEPTONS
METALS
MONOCRYSTALS
PHYSICAL PROPERTIES
POINT DEFECTS
POSITRONIUM
POSITRONS
SILVER
SURFACE CONTAMINATION
SURFACES
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENTS
TRAPS
VACANCIES