Heteroepitaxal Growth Laboratory

Director: Prof. Marjorie Olmstead

Our lab is part of the Condensed Matter Experiment group in the Physics Department at the University of Washington. We are also active participants in the interdisciplinary UW Center for Nanotechnology.

Topics

Research Summary

Approach

The formation of interfaces between crystalline solids with disparate chemical, electronic or structural properties poses numerous challenges, as well as opportunities for investigation of basic scientific issues. Such interfaces control the incorporation of dissimilar materials into a common device structure, such as a chemical or radiation sensor or a three-dimensional integrated circuit.

Development of these emerging technologies is hampered by lack of knowledge about both the formation and the resultant properties of these artificial structures. For example, interface compounds formed during growth may not exist in three-dimensional form, but their unknown properties can dominate the device behavior. The research in Professor Olmstead's group focuses on understanding both the mechanisms of thin film growth and the unique properties of the resultant heterostructures at the atomic level.  Her group also investigates similarities and differences between bulk and nanoscale materials.

Monolayer control of materials growth is obtained with molecular beam epitaxy (MBE), where beams of molecules impinge on a crystalline surface in ultra-high vacuum (UHV) at rates of about 1-100 molecular layers/minute. Using a UHV chamber with combined facilities for MBE and materials characterization, experiments probe the development of electronic, optical, and atomic structure at the monolayer level.  Variable temperature scanning probe microscopy yields nanoscale measurements during the growth process. Other electon, photon and atom spectroscopies give additional information about the complex chemical and physical interactions which govern heterointerface properties, as do measurements of magnetic and transport properties. 


Our primary instrumentation in the basement of the physics building includes an Omicron nanostructure analysis facility largely funded by the Murdock Charitable Trust, which includes interconnected UHV chambers with variable temperature scanning probe microscopy, xray photoemission spectroscopy, low energy electron diffraction, ion scattering spectroscopy and molecular beam epitaxy capabilities.  We also have a PHI Versaprobe imaging xray photoemission system (50 micron resolution), funded by the Micron Foundation, as well as a pulsed laser deposition system for combinatorial materials exploration (also funded by the Micron Foundation).  The Micron Foundation also supported a small-spot xray diffraction system located in the Micron CME lab in Roberts Hall.  All this equipment is shared with other research groups.  We also use a number of national facilities -- the Advanced Light Source, Advanced Photon Source, and Spring-8 synchrotrons, as well as the National Center for Electron Microscopy.

Current Projects

Intrinsic Vacancy Chalcogenides for Spintronic Applications
Phase Change Materials for Nanoelectronics:  A combinatorial approach to mechanistic understanding




This project is a collaboration with Prof. Fumio Ohuchi in Materials Science and Engineering.

This project seeks to create new, silicon-compatible magnetic heterostructures utilizing transition-metal doped semiconducting chalcogenides for nanoelectronic and spintronic applications.  This project focuses on heteroepitaxial growth of TM-doped III-VI based semiconductors and on the inter-related structural, electronic, and magnetic properties of this largely unexplored class of materials.  The research is aimed both at developing technologically relevant materials and at understanding the nanoscale mechanisms underlying their novel properties. The research seeks to elucidate mechanisms of III-VI thin film growth, as well as to understand origins of possible magnetism in these  materials, and to develop III-VI growth technology and materials characterization to the stage where these materials may be utilized for spintronic applications.  Development of this new generation of materials will require new, basic knowledge about the interacting constraints that control their electronic, optical and structural properties. 

The primary goals of this project are:
This research will advance knowledge regarding nanoscale mechanisms for magnetization in dilute magnetic semiconductors, doping and compensation in intrinsic vacancy compounds, heteroepitaxial stabilization of metastable crystal structures, and interface mixing and charge localization at interfaces between strongly dissimilar materials. By exploring the physics and materials science of novel materials at the frontier of device applications, where observation of quantum phenomena requires high materials quality and possibilities for device applications are controlled by nanoscale physics, knowledge is generated that is generally applicable to other systems.

This work has been funded by the NSF through grant DMR-0605601 (Summary Abstract)

This research project utilizes Combinatorial Materials Exploration to develop new phase-change materials.  The effort centered at UW focuses on intrinsic vacancy III-VI materials, especially In2Se3 and Ga2O3.  In2Se3 is of interest for non-volatile resistive memory, as it undergoes a resistivity change of 105 between the crystalline and amorphous phases.  Ga2O3 is of interest both for its transparent conductivity, and for the ability to tune that conductivity through vacuum or oxygen annealing.  Our research seeks to understand the mechanisms for this change, both in thin films and in confined nanostructures, as well as to explore the role of stoichiometry, impurities and processing conditions on this transition.  In addition, we seek to develop appropriate data protocols for combinatorial materials exploration as part of a Materials World Network program.

The scientific and technological goals for this project are:

In addition to its scientific and technical goals, the collaboration aims:
This work is funded by the NSF through grant 0710641 (Summary Abstract).

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Publications since Arriving at UW

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Selected Recent Presentations

AVS 2010:

APS 2010:

AVS 2009:
 AVS 2008:
AVS 2007:

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Current Lab Members

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Lab Ph.D. Alumni

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Awards

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Acknowledgments

Research in the Heteroepitaxial Growth Lab is funded by the National Science Foundation
  • DMR 0605601:  Intrinsic Vacancy Chalcogenides for Spintronic Applications
  • DMR 0710641:  Materials World Network:  Phase change materials for nanoelectronics: A combinatorial approach
    to mechanistic understanding
    • We are also grateful for equipment-based support:
  • The Murdock Charitable Trust, for the Scanning Probe Microscopy System (1999-2000)
  • The Micron Foundation, for the Micron CME Lab and its Annex in the Physics basement
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