Nanomechanics & Transport

People

  • Oscar Iglesias-Freire, PhD
  • Yoichi Miyahara, Research associate

Research

A combination of an atomic force microscope (AFM), scanning tunneling microscope (STM) and field ion microscope (FIM), which is unique worldwide so far, is used to characterize and manipulate samples and tips on an atomic scale.  These microscopes are incorporated in a ultra high vacuum surface science system to achieve control over the cleanliness of the sample and tip.  Samples are prepared and characterized in a UHV sample preparation chamber using a UHV evaporator and Scanning Auger Microscope.

In our first proposed experiment, one contacting wire is an atomically characterized (by STM) surface, while the second contact is made by the field ion microscopy (FIM) characterized tip. The power of this approach is that there are no fudge parameters when comparing experimental results to modeling. We plan to investigate the pressure dependent conductance of organic molecules. The pressure can directly be calculated from the known tip size and the measured applied force. The aim is to find a molecule that has the largest amplification gain for the smallest amount of pressure change. This will be achieved by performing experiments on a few simple molecules such as C60, benzene, porphyrins or alkane thiols. In the future local pressure changes could be brought about by (light activated) confirmation changes of gate molecules.

FIM/STM/AFM Instrumentation

The instruments are housed in a three chamber ultra-high vacuum system with a quick load lock chamber, sample preparation chamber, and measurement chamber. Pictures of the complete system can be found here

Sample Preparation Chamber

  • Scanning Auger Microscope / spectrometer
  • Triple source e-beam evaporator for the deposition of metals and molecules (Omicron EFM-3T)
  • Ion gun and leak valve
  • Sample heating stage
  • Tip heating stage
  • Tip field emission stage

Measurement Chamber

  • Scanning Probe Microscope running in STM current feedback with simultaneous AFM force detection using unique cantilevered samples and interferometric detection of sample deflection
  • FIM built into the same instrument
  • Leak valve and heated quartz tube for helium purification >107 when backfilling for FIM
  • LN2 dewar and cryostat for operation of FIM/STM/AFM at 150K

Recent Publications

W. Paul, Y. Miyahara, and P. Grütter  
J. Vac. Sci. Technol. A 31, 023201 (2013) 

D. J. Oliver, 
  • J. Maassen, 
  • M. El Ouali
  • W. Paul
  • T. Hagedorn
  • Y. Miyahara
  • Y. Qi
  • H. Guo, and 
  • P. Grütter
  • "Conductivity of an atomically defined metallic interface"  
    Proc. Natl. Acad. Sci. U. S. A. 109, 19097 (2012); doi:10.1073/pnas.1208699109



    J.-B. Lalanne, W. Paul, D. Oliver, and P. H. Grütter
    "Note: Electrochemical etching of sharp iridium tips"
    Rev. Sci. Instrum. 82, 116105 (2011)

    Photos

    UHV chamber

    FIM group: Mehdi, Will, Till, Peter, David, Yoichi