Segregation on Annealed R-Cut Sapphire Surfaces
EMSL Project ID
16728
Abstract
We are currently studying step/terrace formations on r-cut sapphire surfaces with miscuts less than 0.5°. These sapphire wafers are used as thin-film substrates in our lab. Through atomic force microscopy we have observed the growth of small features on the surface after high-temperature annealing in air. This analysis shows the features are roughly circular, with diameters typically 100 nm and heights up to 5 nm above the sapphire surface. (See attached figure.) Spectroscopic analysis by methods we have available (XPS and AES) are limited by the small size of these features. We propose to have these samples examined using the ESML’s Interfacial and Nanoscale Science facility. The Scanning Auger Microprobe instrument, if surface charging is not too great, may produce an elemental map of the surface. This will allow us to determine the surface composition of the samples in general, and specifically to find out the chemical makeup of these small, circular features. Another possibility for this analysis would be TEM. Finally, proton induced x-ray emission would allow us to determine the impurities present in the sample. Our present conjecture concerning these circular features is that they are due to irreversible segregation of a bulk contaminant such as calcium. It is also possible that they are caused by impurities in the crucible or furnace atmosphere during the anneal.
Project Details
Project type
Exploratory Research
Start Date
2005-12-07
End Date
2006-11-13
Status
Closed
Released Data Link
Team
Principal Investigator