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Current
research concerns optical metrology of solids, especially based on
ellipsometric principles, and device issues typically concentrating
upon nanotechnology requirements.
Optical metrology:
We have built a
spectroscopic ellipsometer operating from 5 eV to 9 eV, and used this
to study the optical properties of bulk materials and thin films
relevant to device technology. A major emphasis has been on high-k gate dielectrics. We are developing a scanning probe
ellipsometer capable of 1 nm lateral resolution.
Recent publications in this area
Measurement of
the band offsets between amorphous LaAlO3 and silicon, L.
F. Edge and
D. G. Schloma),
S. A. Chambers, E. Cicerrella and J. L. Freeoufb), B.
Holländer and J. Schubert, Applied Physics
Letters 84, 726 (2004).
Separate and
Independent Control of Interfacial Band Alignments and Dielectric
Constants in Transition Metal Rare Earth Complex Oxides, G. Lucovsky,
Y. Zhang, J. L. Whitten, D. G. Schlom, and J. L. Freeouf, Microelectronic Engineering 72, 288 (2004).
¡°Optical
Properties of La-Based High-K Dielectric Films,¡± E. Cicerrella, J.L.
Freeouf, L.F. Edge and D.G. Schlom, T. Heeg, J.
Schubert, and S.A.
Chambers, Journal of Vacuum
Science and Technology A. 23, 1676 (2005).
¡°Spectroscopic
studies of the electrical structure of transition metal and rare earth
complex oxides,¡± Lucovsky, G.,
Zhang, Yu;
Whitten, J.L.;
Schlom, D.G.;
Freeouf, J.L.
Physica E: Low-Dimensional Systems and
Nanostructures, 21, 712-716 (2004).
¡°Rare-earth scandate single- and multi-layer thin films as
alternative gate oxides for microelectronic applications,¡± Heeg, T.;
Wagner, M.;
Schubert, J.;
Buchal, Ch.;
Boese, M.;
Luysberg, M.;
Cicerrella, E.;
Freeouf, J.L.,
Microelectronic
Engineering, 80, n SUPPL., Jun 17, 2005, (14th
Biennial Conference on Insulating Films on Semiconductors,) p 150-153 (2005).
¡°Growth
and
Properties of Epitaxial Rare-Earth Scandate Thin Films," by T. Heeg, J.
Schubert, C. Buchal, E. Cicerrella, J.L. Freeouf, W. Tian, Y. Jia, and
D.G Schlom, Applied
Physics A. 83, 103 (2006).
Dielectric and
Optical Properties of Epitaxial Rare-Earth Scandate Films and Their
Crystallization Behavior, H. M. Christen, G. E. Jellison, Jr., I.
Ohkubo, S. Huang, M. E. Reeves, E. Cicerrella, J. L.
Freeouf, Y. Jia, and D. G. Schlom, Applied
Physics Letters 88, 262906 (2006).
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Device Physics and Nanotechnology:
Current efforts have
concentrated upon properties of semiconductor nanowires and solar cell
design. Contact issues have been a major emphasis and will be again.
Selected publications in these areas
Contacts:
Ideal
Schottky Diodes on Passivated Silicon, M. Wittmer
and J. L. Freeouf, Phys. Rev Lett. 69, 2701 (1992).
Schottky
Barriers: An Effective Workfunction Model, J. L. Freeouf and J. M.
Woodall, Appl. Phys. Lett. 39,
727 (1981).
¡°Effective"
Barrier Heights of Mixed Phase Contacts: Size Effects, J. L. Freeouf,
T. N. Jackson, S. E. Laux, and J. M. Woodall, Appl. Phys. Lett.
40, 634 (1982).
Effect
of
Interfacial Hydrogen in CoSi2/Si(100) Schottky Barrier
Contacts, M. O. Aboelfotoh, A. D. Marwick, J. L. Freeouf, Phys.
Rev. B49, 10753 (1994).
Microscopic
Compound Formation at the Pd‑Si (111) Interface, J. L. Freeouf, G. W.
Rubloff, P. S. Ho, and T. S. Kuan, Phys. Rev. Letters
43, 1836 (1979).
Solar Cells:
Radiation hard and gravimetric efficient thin film InP
solar cells, Sun Yanning,
Woodall, J.M., Freeouf, J.L. and Walters, R.J., Proceeding of the 29th Photovoltaic Specialists Conference,
p.994 ¨C997 (2002).
Double Graded, Drift Dominated InP Solar Cells, Yanning
Sun, Jerry M. Woodall, Jeffrey H. Warner, Robert J. Walters, John L. Freeouf, Aristo Yulius, and Guohua
Li, 3rd World Conference on Photovoltaic Energy Conversion, Osaka,
Japan, May 12-16, 2003, Proceedings of
the 3rd World Conference on Photovoltaic Energy Conversion, 726
(2003).
¡°Extreme
radiation hardness and light-weighted thin-film indium phosphide solar
cell and its computer simulation,¡±   Li, Guohua; Yang, Qingfen; Yan, Zonglin; Li, Wennian; Zhang, Shan; Freeouf, John; Woodall, Jerry M., Solar Energy Materials
and Solar Cells
75,  307
(2003).
Nanowires:
Atomic
Layer
Deposition of ZnSe/CdSe Superlattice Nanowires, R. Solanki, J. Huo, J.
L. Freeouf, and B. Miner, Applied Physics Letters 81, 3864
(2002).
Directed growth
of nickel silicide nanowires, C. A.
Decker, R.
Solanki,a)J. L.
Freeouf, and J. R.
Carruthers, D. R. Evans, Applied Physics
Letters 84, 1389 (2004).
¡°Electroluminescence
from silicon nanowires,¡± Huo, J.
Solanki, R.,
Freeouf, J.L.;
Carruthers, J.R.,
Nanotechnology 15,
1848 (2004).
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