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Near-field microwave microscopy on nanometer length scales Atif Imtiaz,a
 

Summary: Near-field microwave microscopy on nanometer length scales
Atif Imtiaz,a
Marc Pollak, and Steven M. Anlage
Center for Superconductivity Research, Department of Physics, University of Maryland, College Park,
Maryland 20742-4111
John D. Barry and John Melngailis
Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland
20742
Received 9 August 2004; accepted 8 November 2004; published online 20 January 2005
The Near-field scanning microwave microscope NSMM can be used to measure ohmic losses of
metallic thin films. We report on the presence of an interesting length scale in the probe-to-sample
interaction for the NSMM. We observe that this length scale plays an important role when the
tip-to-sample separation is less than about 10 nm. Its origin can be modeled as a tiny protrusion at
the end of the tip. The protrusion causes deviation from a logarithmic increase of capacitance versus
a decrease in the height of the probe above the sample. We model this protrusion as a cone at the
end of a sphere above an infinite plane. By fitting the frequency shift of the resonator versus height
data which is directly related to capacitance versus height for our experimental setup, we find the
protrusion size to be 35 nm. For one particular tip, the frequency shift of the NSMM relative to 2
m away saturates at a value of about 1150 kHz at a height of 1 nm above the sample, where the
nominal range of sheet resistance values of the sample is 15150 . Without the protrusion, the

  

Source: Anlage, Steven - Center for Superconductivity Research & Department of Physics, University of Maryland at College Park

 

Collections: Materials Science