We develop a theoretical description of the heat flux between a miniaturized sensing tip and a structured surface of different temperature at nanometer distances. A near-field effect known as “photon tunneling” then allows one to obtain images of the surface. Because such a “photon tunneling microscope” is sensitive to the electromagnetic local density of states, the information acquired in this manner differs from that accessible to a conventional electron tunneling microscope, which maps the electronic local density of states.

This work is performed in close collaboration with the experimental Energy and Semiconductor Research Group headed by Jürgen Parisi. Under the guidance of Achim Kittel, this group has developed a functioning Near-Field Scanning Thermal Microscope (NSThM), which has the unique capability of assessing the extreme near-field regime. Our joint Oldenburg Project aims at a comprehensive understanding of the working principles of this novel instrument. The figures below show a theoretically reconstructed (left) and an experimentally measured (right) thermal image of a nanostructured surface.

• Achim Kittel, Wolfgang Müller-Hirsch, Jürgen Parisi, Svend-Age Biehs, Daniel Reddig, and Martin Holthaus:
  Near-Field Heat Transfer in a ScanningThermal Microscope.
  Phys. Rev. Lett. 95, 224301 (2005).
  arXiv:1103.3278v1
   
• Svend-Age Biehs, Oliver Huth, and Felix Rüting:
  Near-field radiative heat transfer for structured surfaces.
  Phys. Rev. B 78, 085414 (2008).
  arXiv:1103.3050v1
   
• Achim Kittel, Uli Wischnath, Joachim Welker, Oliver Huth, Felix Rüting, and Svend-Age Biehs:
  Near-field thermal imaging of nano-structured surfaces.
  Appl. Phys. Lett. 93, 193109 (2008).
  Also selected editorially for the November 24, 2008 issue of the Virtual Journal of Nanoscale Science & Technology.
  arXiv:1103.3059v2
   
• Svend-Age Biehs, Oliver Huth, Felix Rüting and Martin Holthaus:
  Spheroidal nanoparticles as thermal near-field sensors.
  J. Appl. Phys. 108, 014312 (2010).
  arXiv:1103.4511v1
   
• Felix Rüting, Svend-Age Biehs, Oliver Huth, and Martin Holthaus:
  Second-order calculation of the local density of states above a nanostructured surface.
  Phys. Rev. B 82, 115443 (2010).
  arXiv:1103.3221v1