Understanding the fundamental physical properties of nanostructures is central to the rational development of functional devices, enables an efficient mechanism through coupling to synthetic studies for rapid variation and optimization of properties, and is central to discovery of potentially new device concepts. The Lieber group is committed to and actively engaged in studies of the fundamental electronic and optical properties of nanowire using a variety of state-of-the art measurement techniques. Particular emphasis in this general area is being placed on understanding transport of electron and hole charge carriers through one-dimensional nanowire systems, which is critical to nanoelectronic devices and systems, and understanding how the confinement of photons and charge carriers within nanowires affects optical properties, which is central to photonic devices and systems.

• Transport studies of nanowire materials. We have a very active program focused on understanding the transport of charge carriers through homogeneous and modulated nanowire structures from room to millikelvin temperatures. Current efforts are focused on defining fundamental limits in these one-dimensional systems, for coherent and ballistic transport, that are relevant to possible applications as high-performance field-effect transistors for digital electronics, as well as more exotic spin and quantum based electronics. In addition, there is considerable effort and interest in exploring one-dimensional electron and hole gas systems, which may be realized using core-shell nanowire structures, developing coupled quantum systems where the coupling and system size are defined by synthesis not lithography, and exploring correlation effects and spin-based transport.
  
  
• Optical studies of groups III-V and II-VI nanowire materials. We are also actively engaged in steady-state and time-resolved optical studies of nanowires. These studies are being carried out at the single nanowire level, which enables detailed information to be obtained about the intrinsic optical properties without ensemble broadening present in lower resolution measurements. Current efforts are focused on defining fundamental mechanisms of lasing in homogeneous, axial- and radial-modulated nanowire structures, which are critical to further development of nanoscale electrically-driven lasers, and elucidating principles underlying transmission and coupling in subwavelength active nanowire structure relevant to a wide-range of integrated nanophotonics systems. There is also ongoing efforts and interest in understanding nanoscale light emitting diodes and single photon sources based on nanowire structures.
  
  
• Scanning probe microscopy investigations of 1D systems. We have strong efforts focused on understanding the local electronic structure and electronic properties of one-dimensional nanowire and nanotubes using scanning probe microscopy techniques such as low-temperature scanning tunneling microscopy (STM), electrostatic force microscopy (EFM) and scanning gate microscopy (SGM).

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