Long jumps in surface diffusion on tungsten(211)

The length of the jumps executed by atoms during diffusion is important for understanding atomic transport in crystal growth. Molecular dynamics simulations suggest that atomic jumps longer than a nearest-neighbor spacing should contribute at elevated temperatures. Attempts have been made in the past to deduce the jump length from the prefactor in the Arrhenius plot, but this is quite an uncertain procedure. To establish the possible contribution of long jumps in atomic migration, observations have been made in a field ion microscope of single adatoms on W(211), where diffusion is one-dimensional. Experiments with W, Pd, and Ni adatoms reveal that diffusion obeys a simple Arrhenius relation, with entirely normal prefactors. However, a more definitive way of finding jump lengths is to measure and analyze the distribution function for atomic displacement. Such experiments have been carried out and show that W moves entirely by single jumps, but Ni has occasional double jumps even at the lowest temperature examined. These double jumps make up 6% of the total. As the temperature is increased the number of long jumps for Ni is unchanged, while Pd shows a large increase in the numbers of long jumps. At 133 K, jumps spanning two nearest-neighbor distances make up 15% of the total jumps for palladium, and jumps spanning three nearest-neighbor distances make up 12% of the total. These results are the first indication of long jumps in one-dimensional diffusion.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Materials Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Senft, Donna Sue Cowell

Contributors dc:contributor

• Ehrlich, Gert

• Chemistry, Physical
• Physics, Condensed Matter
• Engineering, Materials Science

Statement dc:rights

• Copyright 1995 Senft, Donna Sue Cowell

Language dc:language

eng

Identifier

AAI9522172
(UMI)AAI9522172

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/21508