Michael O. Thompson

Associate Professor, Materials Science and Engineering

130 Bard Hall, 607/255-2365

B.S. 1979 (California Institute of Technology); M.S. 1982, Ph.D. 1984 (Cornell)

Biography

Thompson was appointed to the faculty in January, 1984, upon completion of his graduate program. As a graduate student, he worked for IBM during the summers, and he had fellowships from IBM and from the National Science Foundation. He began his academic career as the recipient of one of the first IBM Faculty Development Awards. These awards, intended to encourage untenured professors to remain in academic positions, provide support for a semester of full-time research. He was also chosen by the National Science Foundation for a 1984 Presidential Young Investigator award. Thompson is a member of the American Physical Society and the Materials Research Society.

Research Interests

The current research interests of my group are directed toward two general areas: (1) kinetics of nonequilibrium crystallization phenomena, and (2) growth and properties of germanium-silicon alloys.

The first area focuses on the kinetics of crystal-growth processes, nonequilibrium impurity segregation, and nonequilibrium phase transformations that result from either surface melting produced by pulsed lasers or nonequilibrium growth induced by MeV ion beams. Directed-energy sources such as lasers allow controlled melting of the near-surface region, with crystal solidification rates from 1 to 100 m/s, or temperature-quench rates in excess of 1012 K/s. Such quench rates are sufficient to access metastable phases in binary alloys and to quench metastable allotropes of elements such as silicon.

We study these rapid phase transformations by making direct, real-time measurements of temperature and transformation velocity at the liquid-solid interface during melting and solidification. Interface probes yield detailed information on many aspects of the solidification process, including several unexpected transformation modes. We have studied explosive crystallization of amorphous Si, internal melting of impurity-doped Si, homogeneous nucleation, and orientation dependence of amorphous Si quench.

Similar nonequilibrium growth conditions can be established in the solid-phase by MeV ion irradiation of amorphous Si. Such irradiation leads to crystallization and segregation of impurities analogous to that observed following laser melting. Currently we are studying the behavior during this transformation of fast-diffusing impurities such as Cu, Ag, and Au. Our goal is to understand how the ion beam modifies the interface structure and hence the kinetics of the amorphous-to-crystalline transformation.

The second area of interest involves the growth and characterization of GeSi alloys. This represents an important new departure in semiconductor research, since these alloys make it possible to fabricate heterojunction transistors from simple Column IV semiconductors. We are attempting to use laser-assisted processes to grow strained layers of the alloys. In addition, we are studying the crystallization and impurity-diffusion kinetics in both strained and unstrained alloys.

Current Research Projects

Rapid Phase Transitions in Doped Semiconductors (National Science Foundation through the Materials Science Center at Cornell)
Other participant: J. Yater, graduate student

Joint Sandia/Cornell Experiments on Laser Melting (Sandia National Laboratories)
Other participant: M. Uttormark, graduate student

Growth and Characterization of SiGe Alloys (Semiconductor Research Corporation)
Other participant: P. Smith, graduate student

Temperature Measurements during Pulsed Excimer Photoablation of Polymers and Ceramics (IBM )
Other participant: D. Brunco, graduate student

Selected Publications

  • Thompson, M. O., P. S. Peercy, J. Y. Tsao, and M. J. Aziz. 1986. Rapid solidification studies of a model alloy system. Applied Physics Letters 49:558.
  • Custer, J. S., M. O. Thompson, and P. H. Bucksbaum. 1988. Solid-phase epitaxy of laser amorphized silicon. Applied Physics Letters 53:1402.
  • Peercy, P. S., J. Y. Tsao, S. R. Stiffler, and M. O. Thompson. 1988. Explosive crystallizatiopn in amorphous Si initiated by long pulse-width laser irradiation. Applied Physics Letters 52:203.
  • Stiffler, S. R., M. O. Thompson, and P. S. Peercy. 1988. Supercooling and nucleation of silicon after laser melting. Physical Review Letters 60:2519.
  • Custer, J. S., M. O. Thompson, and J. M. Poate. 1989. Segregation of Ag and Cu during ion-beam and thermally induced recrystallization of amorphous Si. Materials Research Society Symposium Proceedings 128:545.
  • Yater, J. A., and M. O. Thompson. 1989. Orientation dependence of laser amorphization of crystal Si. Physical Review Letters 63:2088.
  • Stiffler, S. R., M. O. Thompson, and P. S. Peercy. 1990. Nucleation of amorphous Ge from supercooled melts. Applied Physics Letters 56:1025.

    • Last revised: 11/7/94