An ab initio study of the electron affinity of diamond
surfaces.
MJ Rutter, J Robertson. Accepted by Computational Materials Science
(Elsevier Science).
This is the text of the article as submitted to the journal. Their
copyright transfer prevents me from publishing the final version
in this form. MJR.
Abstract
Diamond surfaces combine chemical inertness with, in some cases, a
negative electron affinity. Such surfaces have great potential for use
on cold cathodes in flat displays. We present ab initio plane
wave electronic structure calculations which enable us to predict the
electron affinities of many different diamond surfaces with various
terminations and reconstructions. Such calculations give good accuracy
and enable the study of perfect surfaces with a range of terminating
species so that the effect of the passifying layer can be readily
seen. Results for the (100) and (111) surfaces will be presented,
giving a range of surfaces more comprehensive than previously
published. We find that the electron affinity varies by over 5.5V
between oxygen and hydrogen coverings, and that this magnitude of
variation can be understood as simply a rising from surface dipoles
such as polarised covalent bonds would be expected to produce. A brief
discussion is given of some of the technical points of performing such
a calculation, which combines ab initio LDA work with experimental
results for the band-gap for diamond in order to estimate accurately
the position of the unoccupied levels.
This preprint is available as gzipped postscript
here.
The paper was presented at E-MRS97 in Strasbourg. It was written whilst
I was employed by the Department of Engineering.