• About Us

• Research
  • Scanning Probe
    Recognition Microscopy
  • Nanobiology
  • Nanoelectronics
  • Fundamental Radiation Interactions
  • Undergraduate Research Program
  • International Research

• Publications

• Facilities
  • Electronic and Biological Nanostructures Laboratory
  • W. M. Keck Microfabrication Facility
  • The Center for Advanced Microscopy
  • Electron Microbeam Analysis Laboratory
  • National Superconducting Cyclotron Laboratory

• Group Members

• Collaborators
  • Michigan State University
  • National
  • International

• Group News

• How to Find Us
  • Address & Map
  • Express Mail Address
  • Conference &
    Seminar Schedule

NANOELECTRONICS: Multiphase GaN Nanowires and Nanocircuits

Multiphase Gallium Nitride Nanowires and Nanocircuits (NASA, NSF)

Significance of Research

Our research group has contributed the first recognition, characterization, and applications of multiphase gallium nitride nanowires. This work has revealed that the internal structure of these nanowires combines single crystal, single phase 1D zinc-blende and wurtzite domains that span the full length of the nanowire system. Multiphase nanowires may have novel properties that augment and may be superior to single phase nanowires in device applications. We have also been the first group to investigate the unique properties of multiphase gallium nitride nanowires in electronic and mechanical applications. Multiphase Gallium Nitride Nanowires is a fruitful collaborative effort with the research group of Professor Joshua Halpern at Howard University, who developed the catalyst-free vapor-solid nanowire growth process.

Multiphase Gallium Nitride Nanowires

Our group investigates gallium nitride (GaN) nanowires grown using a catalyst free vapor-solid mechanism. While analyzing the GaN nanowires, which were initially thought to be single-phase wurtzite, our group discovered a new multiphase GaN nanowire structure. The multiphase nanowires incorporate both the zinc-blende and wurtzite phases simultaneously in a longitudinal, self-assembled configuration that extends the entire length of the nanowire [1]. The new multiphase nanowire configuration was discovered and then proved by a thorough investigation using high resolution transmission electron microscopy (HRTEM) with quantitative electron energy loss spectroscopy (EELS) and energy dispersive X-ray spectroscopy (EDS), selected area electron diffraction (SAED), cross section preparation by dual-beam focused ion beam (FIB), JAVA electron microscopy simulation (JEMS), fast Fourier transforms (FFTs), cathodoluminescence (CL); atomic force microscopy (AFM), and scanning electron microscopy (SEM). PICTURE+ CAPTION THIS PARAGRAPH-RIGHT

Details of the internal multi-phase configurations within the nanowire could not be fully elucidated by plain view HRTEM and therefore new studies using state of the art dual beam focused ion beam (FIB) techniques to create nanowire cross sections for analysis were performed by our group. After diligent, meticulous work, fabrication of several nanowire cross-sections that unveiled the internal nanowire structure in clear atomic-resolution detail was achieved. The cross sections were then analyzed, and the crystallographic configuration within each nanowire was determined. A totally coherent interface has been present in all samples investigated to date, which may provide stability for the multiphase homostructure. The influence of the newly discovered nanoscale nucleation sites on multiphase nanowire growth and orientation is also under investigation. [2]

Device Applications of Multiphase Gallium Nitride Nanowires

The multiphase structure has interesting implications on the electronic transport properties of the nanowire. In studying these properties, nanowire field effect transistors were fabricated using electron beam lithography, with the multiphase GaN nanowires as the semiconducting component. Two- and four- point nanoprobe investigations of the electronic properties were carried out in collaborative partnership with Zyvex Corporation, Richardson, TX and Keithley Instruments Cleveland, OH. Individual nanowires were also probed with the nanomanipulator, and indicated a possible phase-specific transport mechanism where carriers seemed to be confined to a certain crystalline phase within the nanowire [3].

Current Research

Multiphase Gallium Nitride Nanowires: We are investigating a new growth mechanism that can account for stable multiphase GaN nanowire formation. Stay tuned!

Device Applications of Multiphase Gallium Nitride Nanowires: We are investigating electron transport using nanoprobe I-V characterization , cathodo- and photo- luminescence (collaboration with Strathclyde University, Scotland, and NASA JPL) and theoretical investigations (collaboration with Purdue University). All of these investigations are aimed at answering one question: where are the dang electrons?!

References: Multiphase Gallium Nitride Nanowires and Nanocircuits

• [1] Benjamin W. Jacobs, Virginia M. Ayres, Mihail P. Petkov, Joshua B. Halpern, MaoQe He, Andrew D. Baczewski, Kaylee McElroy, Martin A. Crimp, Jiaming Zhang, Harry C. Shaw, "Electronic and Structural Characteristics of Zinc-Blende Wurtzite Biphasic Homostructure GaN Nanowires", Nano Lett., Vol. 7, No. 5, pp. 1435-1438 (2007)
• [2] Benjamin W. Jacobs, Virginia M. Ayres, Martin A. Crimp, Kaylee McElroy, Maoqi He, Joshua B. Halpern, "Vapor-Solid Growth of Multiphase Zinc-Blende Wurtzite Gallium Nitride Nanowires", submitted to Nano Letters, 2008
• [3] B W Jacobs, V M Ayres, R E Stallcup, A Hartman, M A Tupta, A D Baczewski, M A Crimp, J B Halpern, M He and H C Shaw, "Electron Transport in Zinc-Blende Wurtzite Biphasic Gallium Nitride Nanowires and GaNFETs", Nanotech., Vol. 18, 475710 (6 pp) (2007)