Associate Professor Paul Lyman
	plyman@uwm.edu Personal Home Page Telephone: (414) 229-4626 Room: 484

 

 

Associate Professor Paul Lyman conducts research on the structure and growth of novel thin films of electronic materials.  The structure of the surface and its effect on further film growth are particular emphases of his efforts.  Past studies have focused on high-resolution structural studies of adsorbate structure on semiconductors.  Present efforts are aimed at developing growth methods for high-quality dielectrics for ultra-large scale integrated circuits (ULSI).

Lyman employs a breadth of analytical techniques in these experiments. At UWM, he relies on x-ray photoemission spectroscopy (XPS) to elucidate the chemical environment of the surfaces and thin films under study.  Surface ordering is probed using low-energy electron diffraction (LEED).  Surface periodicity and strain relaxation can be monitored in real time during growth using reflection, high-energy electron diffraction (RHEED).  Funds have been secured to purchase an electron energy analyzer for RHEED, allowing the chemical and structural environment of a growing surface to be monitored during deposition.

Professor Lyman also uses a host of synchrotron-based analytical methods.  A synchrotron is a machine that accelerates charged particles to speeds near the speed of light in order to produce a powerful beam of x-rays.  Lyman uses several such machines constructed by the Department of Energy, including the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory near New York, and the Advanced Photon Source (APS) at Argonne National Laboratory near Chicago.  Using these x-ray sources, Lyman probes surfaces and films using grazing-incidence x-ray diffraction (GIXD), x-ray standing waves (XSW), and surface extended x-ray absorption fine structure (SEXAFS).  Beamtime on such machines is granted on a competitive basis, and Lyman conducts several experiments at synchrotrons per year.

Using these techniques, Lyman has uncovered surface phenomena of interest for electronic materials.  For example, he recently found a novel surface passivation scheme for Te on Ge(001) that helps to explain why Te can behave as an efficient surfactant for epitaxial growth of Ge on Si.  Previous to that, Lyman used a Bi surfactant to allow the construction of a SnGe alloy that is thermodynamically unstable.  This compound, though not found in nature, is predicted to have a direct, tunable bandgap that would be useful for construction of inexpensive optoelectronic devices.  Lyman's current interest is in growing advanced dielectric (insulating) materials that are both compatible with conventional silicon processing methods and can be used to produce devices that are smaller than those now possible.  He has been exploring the use of Hf (hafnium), and compounds of Hf, Si, and O (silicides and silicates). Growth is being carried out using conventional elemental deposition techniques and new gas-source growth methods.

Lyman completed his undergraduate and graduate education at the University of Notre Dame and the University of Pennsylvania, respectively.  He conducted post-doctoral studies at Oak Ridge National Laboratory and Northwestern University.  He has published over 30 refereed papers in surface and thin-film science.  Lyman was recently awarded a NSF CAREER award to support his research and teaching.