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| Irene Group Recent Results | |
| Complex Oxides | |
Over
several years we have developed a world wide unique film deposition
and characterization strategy that enables the controlled formation
and characterization of thin films of complex materials. The hardware
consists of a multi target sputter deposition subsystem housed
within a turbomolecular pumped vacuum system. Integrated with this
film deposition system is a low energy (5-15 keV) ion beam analysis
subsystem capable of determining surface composition and structure
and a spectroscopic ellipsometry system capable of obtaining optical
properties of surfaces and films and of determining film growth
dynamics. Thus far we have studied O dynamics within high temperature
superconductor oxide films and the formation dynamics of high dielectric
constant oxides for use in integrated circuits. 
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| Ultra-Thin Film Dielectrics | |
We have developed novel methods for determining film thickness for films less than 7 nm thick using a combination of Fowler-Nordheim electron tunneling and spectroscopic ellipsometry. The high electric field electron tunneling leads to tunnel current oscillations that are analogous to the standing waves found in optical etalons that are sensitive to the path length in the etalon. The thickness' obtained can be used in combination with ellipsometry to obtain the almost impossible to measure refractive index for the ultra-thin films. These techniques combined with atomic force microscopy and
a novel technique developed in our laboratory, spectroscopic
immersion ellipsometry, have been used to measure film thickness,
film growth dynamics in the ultra-thin film regime and the evolution
of interfacial roughness with film formation processes. All of these
properties impact the resulting electronic properties of the films.
For roughness evaluation a novel Fractal analysis was developed in
order to distinguish the roughness found on various samples.
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| Plasma Grown and Deposited Thin Films | |
We have discovered that by using a combination of plasma techniques
such as electron cyclotron plasma with radio frequency plasma,
we are able to control the position of N in nitrided SiO2.
Nitrided oxides are important in microelectronics because the N
prevents the out diffusion of Si dopant through the oxide which
would alter electronic device properties. However when SiO2 is
nitrided much of the N has been found at the Si-SiO2 interface
where it gives rise to electronic instabilities. Now we are able
to "engineer" the position of N in an SiO2 film
through the use of multiple plasma film growth techniques and an
understanding of the nitridation mechanism. 
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Department of Chemistry
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Last Updated:
January 17, 2007
© 2006 University of North Carolina at Chapel Hill Content Manager: chemcontent@unc.edu |