THE CRYSTALLOGRAPHY OF IMPURITY ADSORPTION ON COPPER SURFACES
Abstract
The object of the investigation was to determine the sites at which impurity adsorption occurs on crystalline surfaces. This was done by measuring the variation of surface free energy with orientation. A relation between the torque, chemical potential, surface excess, and orientation was derived. Methods discussed for determining surface torques by measuring dihedral angles at grooves where twin boundaries and grain boundaries intersect surfaces. Measurements were made of relative torques, on copper surfacess for the range of oxygen pressures of 10 to the -22 to 10 to the -13 power atmosphere at 1000 C using water hydrogen mixtures. Increasing oxygen pressure was found to increase the magnitude of the torque on the (111) and (100) orientations. This indicates preferential adsorption at a range of orientations on the smooth, low index (100) and (111) surfaces rather than on stepped surfaces of orientations different from the low index orientations. A calculation based on a simple model of the surface indicates that about a half monolayer of oxygen atoms is adsorbed on the (111) surface. Measurements of torques after annealing in an atmosphere containing hydrogen sulfide showed that sulfur adsorption decreases the torque near (100) while not affecting that near (111).
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1963
- Accession Number
- AD0407276
Entities
People
- P. G. Shewmon
- W. M. Robertson
Organizations
- Carnegie Institute of Technology