Collective Behavior in Ordered Arrays of Nanostructures - Physics and Technology Opportunities

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This project will study the collective behavior of coupled two-dimensional lateral superlattices of highly ordered nanostructures, in both theory and experiment. Due to significant flexibility in the choice of nanostructure materials, these systems' collective behavior could be of either electronic or magnetic nature. These unique nanolattices have potential technological implications for new optoelectronic, nanoelectronic and computational devices. Over the past year, a new non-lithographic template fabrication method has been developed to produce highly ordered arrays or two-dimensional lateral superlattices of nanostructures-metal and semiconductor wires, and carbon nanotubes. Building on this capability, new experimental and theoretical investigations are needed to assess the scientific and technological opportunities which this new fabrication capability provides; additionally, the fabrication technology itself needs refinement. The main focus in this project is to understand the collective behaviors and interactions which take place within these nanolattices. This project will advance the goals of NSF Electronics, Photonics, and Device Technologies program by exploring device functions of individual nanostructures; extracting system functions from the collective behaviors of a large ensemble of nanoelements; extending the capabilities of our fabrication techniques; and advancing the frontier of this enabling technology for a new generation of electronics. In the fabrication area, the methods of non-lithographic template fabrication of nanostructure lattices will be improved, extending the range of nanostructure sizes and spacings, and hence the couplings between adjacent nanoelements. Engineering and even lithographic steps will be introduced into this otherwise completely natural, self-organized nanofabrication process to enable better observation and/or use of the collective behaviors in the system. Experimental exploration of the properties of these nanostructure lattices will be performed using a variety of approaches, including scanning probe microscopy and spectroscopy (topographical, electronic, magnetic and optical), and broad-area electronic, magnetic and optical measurements. In these experiments, the physical properties of the nanostructures will be characterized in order to help understand the ways in which their collective electronic and magnetic behaviors are manifested. More advanced experiments will attempt to observe the collective behavior directly.On the theoretical front, the electronic behavior of Coulomb-coupled nanostructure arrays, andthe domain ordering behavior of magnetic nanostructures coupled via dipole interactions will bestudied. In each case, the focus and ultimate objective will be to study the collective behaviorarising from the short-ranged interactions, and the implications which this behavior has on thedevice applications of these structures. An exciting long-term possibility is the prospect of usingthe collective behavior of the lattices for useful applications-memory devices, signalprocessing, and possibly even as a testbed for new computation concepts. The theoretical work tobe performed will lay a foundation for these new potential applications, and will guide, informand enable understanding of experimental results. In conclusion, this is an ambitious projectdesigned to lay the foundations for long-term work. While the ultimate goals are extremely far-reaching,the process of investigation has been designed to generate scientifically valuable andtechnologically useful results beginning immediately, and continuing through the duration of theproject.