| |
We are interested in understanding how to fabricate, assemble, and
utilize nanometer scale structures. We work on a diverse set of problems,
and consequently we have extensive collaborations with other groups at
UCLA, at other campuses, and with industrial research groups. For a more
detailed look at my group, click on the photograph at the bottom of the
page, and you will be directed to my group’s full web page. One of our
goals is to learn how to use chemically synthesized quantum dots as
“artificial atoms,” and how to control the properties of the solids that
we get when we assemble these “atoms” into a superlattice. At the heart of
this project is the notion that really only three physical parameters go
in to determining the electronic properties of a crystal: the energy levels
of the atoms (lattice sites); the coupling between adjacent sites; and the
symmetry of the solid. Imagine being able to control each of these
properties separately, and therefore being able to ‘design’ a solid with a
prescribed set of electronic properties! For an atomic solid, this would
amount to being able to tune the electronegativity of a given atom; being
able to control the strength of the covalent interactions within the lattice;
and, being able to choose the crystal structure. While the chemistry of the
periodic table does not lend itself to such control, the chemistry of
“artificial atoms” does. Over the past couple of years we have demonstrated
that it is possible to design solids from quantum dots that have properties
that, while predictable, are completely different from anything that can be
synthesized in the traditional sense. A recent highlight of that work was
our demonstration that we could intentionally design a quantum dot-based
solid that could be reversibly switched between a metal and an insulator
under ambient conditions. For this metal/insulator system, we had to learn
how to carry out experiments in which covalent bonding was actually a
continuously variable experimental parameter. Our current work in this area
involves trying to design unique superconducting solids, and unique magnetic
solids. For the superconducting and ferromagnetic systems, Josephson exchange
coupling, and ferromagnetic exchange coupling, respectively, are the quantum
mechanical analogues to covalent bonding.
A second project going on in my group involves trying to learn how to
chemically synthesize a computer. Our ultimate goal is to build a computer
with approximately the power of 100 high-end workstations on a platform the
size of a grain of sand. This project, which is a collaboration between my
group, Frasier Stoddart’s group, Hewlett Packard Corp., and UC Berkeley, has
progressed very fast over the past year. What once seemed like science fiction
is now looking more and more like science! We have developed a realistic
computer architecture for nearly the entire machine, and we have recently
demonstrated electronically configurable molecular-based logic circuitry. We
hope that, within the next couple of years, we will have developed molecular
based memories and molecular-based communications networks. Some of the
highlights of this work are also listed on the group web page.
Finally, the third project is aimed at understanding the nano-circuitry of
biological systems. We are developing a scanning nonlinear optical microscope
which will allow us to non-invasively probe, at high spatial resolution,
biological electrical functions such as ion-channel switching. This microscope
will have the power to resolve molecular identities and orientations at the
0.1 micron length scale. This project is a collaboration with the UCLA medical
school, and with Rich Saykally at UC Berkeley. This is a young project, and
clearly represents a long-term research commitment. Some of our initial
successes in the form of nonlinear optical micrograph images have been placed
on the group web page.
- J.R. Heath, C.M. Knobler, and D.V. Leff,Pressure/Temperature Phase Diagrams and
Superlattices of Organically Functionalized Metal Nanocrystal Monolayers: The Influence
of Particle Size, Size Distribution, and Surface Passivant,
J. Phys. Chem.B 101, 198 (1997).
- P. Ohara, W.M. Gelbart, and J.R. Heath,Selft-Assembly of Sub-Micrometer Rings
of Particles From Solutions of Nanoparticles, Ang. Chem. Comm. Int. Ed. Engl. 36,
1078 (1997).
- J.J. Shian, R. H. Wolters, and J.R. Heath,Theory of Size-Dependent Resonance Raman
Intensities in InP Nanocrystals, J. Chem. Phys., 106, 8981 (1997).
- T. Vossmeyer, E. DeIonno, and J.R. Heath, Light-directed Assembly of Nanoparticles,
Angew. Chemie Comm. Int. Ed. Engl. 36, 1080 (1997).
- G. Markovich, et al., Parallel Fabrication and Single-Electron Charging of Devices
based on Ordered, Two-Dimensional Phases of Organically-Functionalized Metal Nanocrystals,
Appl. Phys. Lett. 70, 3107 (1997).
- C.P. Collier, S. Henrichs, J.J. Shiang, R.J. Saykally, and J.R. Heath, Reversible
Tunning of Silver Quantum Dot Monolayers Through the Metal-Insulator Transition,
Science, 277, 1978-80 (1997).
- J.R. Heath, P.J. Kuekes, G. Snider, and R.S. Williams, A Defect Tolerant Computer
Architecture: Opportunities for Nanotechnology, Science, 280, 1716 (1998).
- G. Markovich, C.P. Collier, and J.R. Heath, Observation of a Reversible
Metal-Insulator Transition in Ordered Metal Nanocrystal Monolayers by Impedence Spectroscopy,
Phys. Rev. Lett., 80, 3807 (1998).
- C.P. Collier, T. Vossmeyer, J.R. Heath, Quantum Dot Superlattices, Ann. Rev.
Phys. Chem. 49, 371 (1998).
- T. Vossmeyer, X. Jia, E. DeIonno, M. Diehl, X. Peng, A.P. Alivisatos, J.R. Heath, Combinatorial
Approaches Toward Patterning Nanocrystals, J. Appl. Phys., 84, 3664 (1998).
- F. Remacle, C.P. Collier, G. Markovich, J.R. Heath, U. Banin, and R.D. Levine, Networks
of Quantum Nano-Dots: The role of disorder in Modifying Electronic and Optiocal Properties,
J. Phys. Chem. B, 102, 7727 (1998).
- S.H. Kim, G. Markovich, S. Rezvani, S.H. Choi, K.L. Wang, and J.R. Heath, Single-Electron
Structure in MIS Tunnel Diodes Fabricated From CdSe Nanocrystal Monolayers, Applied Physics
Letters, 74, 317 (1999).
- G. Madeiros-Ribeiro, D.A.A. Ohlberg, R.S. Williams, and J.R. Heath, Rehybridization of
Electronic Structure in Compressed 2D Quantum Dot Superlattices, Phys. Rev. B (brief
reports), 59, 1633 (1999).
- S. Henrichs, J. Sample, J. Shiang, C.P. Collier, R.J. Saykally, and J.R. Heath, Positive and
Negative Contrast Lithography of Ag Nanocrystal Monolayers using a Scanning Non-linear Microscope,
J. Phys. Chem. B (cover article) 103, 3524 (1999).
- G. Markovich, C.P. Collier, S. Henrichs, F. Remacle, R. Levine, and J.R. Heath, Architectonic
Quantum Dot Solids, Acc. Chem. Res., 32, 415 (1999).
- R. P. Sear, S.-W. Chung, G. Markovich, W.M. Gelbart, and J.R. Heath, Spontaneous Patterning of
Quantum Dots at the Air-Water Interface, Phys. Rev. E (rapid comm.), 59, R6255 (1999).
- C.P. Collier, E.W. Wong, M. Belohradsky, F.J. Raymo, J.F. Stoddart, P.J. Kuekes, R.S. Williams,
and J.R. Heath, Electronically Configurable Molecular-Based Logic Gates, Science, 285, 391 (1999).
- E.W. Wong, C.P. Collier, M.Behloradský, F.M. Raymo, J.F. Stoddart, and J.R. Heath, Fabrication
and Transport Properties of Single-Molecule Thick Electrochemical Junctions, J. Am. Chem. Soc.
(in press 3/2000).
- S. Henrichs, C.P.Collier, R.J. Saykally, Y.R. Shen, and J.R. Heat, The Optical Dielectric Function
of Ag Quantum Dot Monolayers Compressed through the Metal/Insulator Transition, accepted to J. Am.Chem.Soc.
(to appear 5/2000).
- S.W. Chung, J. Yu, and James R. Heath, Si Nanowire Devices, Appl. Phys. Lett. (to appear 4/2000).
- I. Weitz, J. Sample, R. Ries, E. Spain, and J.R. Heath, Josephson Coupled Quantum Dot Artificial Solids
J.Phys.Chem. B letter, (to appear 5/2000).
Department of Chemistry & Biochemistry
UCLA
Box 951569 (post)
607 Charles E. Young Drive East (courier)
Los Angeles, CA 90095-1569
Heath Group Web Site
|
