Proposed Research

  Cluster I: Tools for Integrated NanoBiology. As biology begins to ask more quantitative and analytical questions about the nature of the cell, it needs new tools to study subcellular structures that have nanoscale dimensions. An important task is to build bridges between the physical and biological sciences. The physical sciences offer to biology new measurement tools and new procedures for analyzing the information obtained. In turn, biology offers to the physical sciences an enormous range of engaging problems, and stimulating examples of very sophisticated, functional biological systems. It also offers the opportunity to think about hybrid systems that combine biological and non-biological components.

Figure 3. A CMOS / Microfluidic chip consisting of a CMOS integrated circuit with a microfluidic system on top. By energizing microcoils, the chip can trap and move magnetic beads and attached cells through the fluid above for cell sorting or the assembly of artificial tissues.

The interface between the biological and physical sciences is one with enormous promise for fundamentally new science, and, ultimately, technology. By supporting collaborations between investigators in DEAS, Chemistry, the Medical School, and the School of Public Health at Harvard, Cluster I will catalyze and expand a series of very effective collaborations across the physical-biological interface.

  Cluster II: Nanoscale Building Blocks. Tremendous progress has been made in the synthesis of nanoscale structuresnanoparticles, nanowires and nanotubesthat serve as building blocks for new devices and applications. However many challenges remain. These include the synthesis of nanostructures with well-defined sizes and shapes, the synthesis of new classes of materials, the in-depth characterization of newly developed nanostructures, the rational organization of these nanostructures into complex functional structures, and the fusion of nanoscale building blocks with state-of-the-art processing techniques, including e-beam lithography and focused-ion-beam sculpting to build novel devices.

Figure 4. Nanoscale building blocks. (a) 2-D array of CdSe nanocrystals. (b) CdSe nanorods. (c) Crystalline La1-xBaxMnO3 nanocubes. (d) Nanometer-sized Pd spherical cups. (e) Single-crystalline VO2 nanobeams. (f) Single-crystalline nanobelts of NbSe2.

A broad multidisciplinary, multi-investigator research program is proposed that is designed to address these challenges. The proposed research is solidly built upon the participants expertise on the synthesis and characterization (both experimental and theoretical) of nanostructured materials. At the core of the program is the rational synthesis of new classes of nanostructures that exhibit new size-dependent properties that are distinct from bulk materials, with an emphasis on semiconductor and metallic nanostructures with unconventional shape, as well as on zero-, one- and two-dimensional nanostructures based on metal chalcogenides that have not been made previously. The incorporation of nanostructures into novel device geometries will constitute another important part. These devices will be used to characterize the physical and chemical properties of nanoscale materials and to test their technological applicability. Understanding the behavior of these nanoscale building blocks through theoretical investigations will be an important part of the proposed efforts, because it is essential for furthering the scientific and technological frontiers of nanomaterials.

Figure 5. Physics Today (Dec. 2003) that contains the review Imaging Electron Flow by Topinka, Heller, and Westervelt.

  Cluster III: Imaging Electrons at the Nanoscale. Electrons inside nanoscale structures display striking quantum behavior that arises from the confinement of electron waves. By visualizing how electron charges and spins move through nanoscale systems, we can understand the fundamental science and develop new quantum devices. These range from a transistor that control an electron charge for single-electronics, or spin for spintronics, to a quantum switch for new approaches to electronics, to fully quantum mechanical dot circuits that control qubits for quantum information processing.

Expected outcomes of this research are: Scanning probe microscopes for imaging electrons inside devices New microscopes and imaging techniques will be developed to see electrons inside nanoscale semiconductor structures, that will be used in the future to characterize and understand new devices. Scientific understanding of electrons inside nanoscale structures. To make new nanoscale devices, we need to understand the motion of electron charges and spins, and the effects of interactions between particles. Research in this cluster will develop this scientific knowledge. Developing new types of heterostructure devices Advances in MBE growth can be used to sophisticated structures including self-assembled InAs quantum dots. Imaging electrons in these structures will enable the development of new devices based on electron charge and spin.