Department of Physics & Astronomy

Fall 2008 Colloquia

 

Keji Lai

Keji Lai

Department of Applied Physics
Stanford University
Near-field Microwave Imaging at the Nanoscale
December 15, 2008, 4PM, Thornton 411

We have developed a near-field scanning microwave microscope using modified atomic-force microscope (AFM) cantilevers with micro-fabricated transmission lines. At giga-Hertz frequencies, local variation of the sample electrical property induces small changes to the tip impedance, which will be detected by sensitive microwave electronics. The spatial resolution of the microscope is then determined by the tip diameter (~100nm) rather then the free space wavelength (tens of centimeters). Using our technique, local electrical imaging has been obtained on doped semiconductors, graphene devices, and complex materials. In particular, we successfully identified multiple phases with distinct conductivity in phase-change In2Se3 nano-ribbon devices, consistent with transmission electron microscopy studies. Finally, a cryogenic version of the microwave microscope has recently been implemented for low-temperature / high magnetic field research.
SF State Home