Welcome to the web site for the Thin Film and
Nanostructured Materials Physics Group, Condensed
Matter Sciences Division at Oak Ridge National Laboratory. Our research
currently addresses two broad scientific challenges, as described
below. For detailed examples of our work please see the Research
and Personnel pages.
Research
on Nanomaterials: Controlled Synthesis and Properties
This research addresses
the central challenge of nanoscale science: the need for fundamental understanding
of how nanomaterials grow and for control of the growth environment, in order
to synthesize materials with new or greatly enhanced properties at attractive
rates. The materials focus currently is on carbon nanotubes/nanofibers and on
mesoscale oxide films/multilayers for greatly improved ionic conductivity. Part
of the research addresses a grand challenge of nanomaterials synthesis: the growth
of macroscopic single wall carbon nanotube (SWNT) crystals, and is carried out
in collaboration with Rice University. The program’s strength is its integration
of three key capabilities: advanced synthesis; time-resolved, in situ diagnostics
during growth; and an arsenal of nanomaterials properties measurement and functionalization
methods. For synthesis, energetic-beam methods of pulsed laser deposition (PLD),
laser vaporization (LV), supersonic chemical beams, and plasma-enhanced chemical
vapor deposition (PECVD) are used, together with thermal CVD. A complete suite
of time-resolved, in situ diagnostic methods is used to obtain information about
the precursor species, temperatures, products, and dynamics of growth in these
environments. For ex situ characterization, the program particularly exploits
unique ORNL Z-STEM/EELS transmission electron microscopy and spectroscopy to
determine structure and composition, now with atomic resolution through aberration
correction. This research also involves strong multidisciplinary collaborations
with other ORNL and university investigators.
Research
on the Emergence of Nanoscale Cooperative Phenomena
This research addresses one of the most important scientific themes of our
time, the fundamental and practical importance of understanding complex,
self-organizing behavior. Its materials focus is on transition metal oxides
(TMOs) and ferroelectric oxides, with special interest in electronically
highly correlated materials that exhibit spontaneous electronic phase separation
on the meso- to nano-scale. Their astonishing range of properties is believed
to result from a variety of possible ground states that lie close together
in energy, so that small changes can create new phenomena. The objective
is to understand and control such effects in order to design artificially
structured TMOs with new combinations of properties. This group's effort
is part of a larger ORNL program that integrates three key capabilities:
advanced synthesis, detailed characterization (nanoscale to bulk), and theoretical
modeling and simulation. For synthesis we have assembled the tools and skills
needed to study nanoscale interactions between different electronic phases
in 3D (thick or coupled films), 2D (isolated thin layers and superlattices),
and quasi-1D (quantum nanowires). For characterization an arsenal of ORNL
scanning probe, electronic, magnetic, and transport properties measurements
is used, together with Z-contrast scanning transmission electron microscopy
(Z-STEM) and electron energy loss spectroscopy (EELS). Aberration-corrected
Z-STEM/EELS now permits “seeing” how electronic properties vary,
locally and quantitatively, across compositional interfaces, with atomic
resolution. For theory, the high-performance computing facilities of ORNL’s
Center for Computational Sciences (CCS) are employed together with collaborations
between in-house and external theorists, to develop computational approaches
suitable for nanoscale highly correlated electronic systems.
Research
Impact
The impact of understanding
self-organizing behavior, and of finding ways to further direct assembly
to make exotic
nanoscale properties useful at the macroscale, clearly will be enormous.
There undoubtedly are general rules of controlled
synthesis and directed assembly to be discovered, and the systematic
application of these will result in the addition of many different
nanostructured materials
to our toolbox. Each success in directed assembly
of nanomaterials will make available a new subset of engineering materials,
and we know from centuries of experience that the discovery and development
of advanced materials always have been the source of new technology.
