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Optical Microscopy

The purpose of the optical microscope is the fast optical control of samples. It can be used in different magnifying degrees.

The optical microscope consists of an ocular lens and several objective lenses, whereas only one is placed in the light path and can be replaced according to magnification. In order to investigate a sample it has to be illuminated additionally in most cases. On the one hand, having transparent samples this can be done using transmitted light, i.e. the light is applied to the sample bottom-up. On the other hand using non transparent samples reflected light is used. In both cases light, which is polarized in one direction can be used in order to examine the samples for example to visualize polarization contrasts.

Typical questions are:

- What is the quality of the sample? Are there contaminations on the sample and does the substrate show microscopic terraces? Is there any crystals growth?

 → Optical micrograph taken with different magnifications.

Figure 1: Images with three different magnifications.

- Are the stamped patterns produced via µCP preserved?

 → Breathing on samples under the microscope.

Figure 2: On the left side the stamped pattern cannot be seen. After breathing on the sample stripes can be seen due to the different hydrophobicity of the applied structure. Within a few seconds the water drops vanish again and the structure becomes invisible once more.

- Is it possible to see growth domaines on the sample?

 → Polarization dependent optical micrographs.

Figure 3: Rotating the polarization of the light the color appearance of different domains changes.

Some exemplary publications of our group where optical microscopy has been utilized are:

• Cell-imprinted substrates direct the fate of stem cells.
  Morteza Mahmoudi, Shahin Bonakdar, Mohammad A. Shokrgozar, Haniyeh Aghaverdi, Raimo Hartmann, Andre Pick, Gregor Witte, and Wolfgang Parak
  ACS Nano 7 (10), 8379-8384 (2013)
  Full Text
• Synthesis and solid-state structures of 6,13-Bis(trifluoromethyl)- and 6,13-Dialkoxypentacene.
  Jonas Schwaben, Niels Münster, Tobias Breuer, Michael Klues, Klaus Harms, Gregor Witte, and Ulrich Koert
  European Journal of Organic Chemistry 2013 (9), 1639-1643 (2013)
  Full Text
• Temperature dependent Optical Properties of Pentacene films on Zinc Oxide.
  Jonatan Helzel, Stephanie Jankowski, Mira El Helou, Gregor Witte, Wolfram Heimbrodt
  Applied Physics Letters 99 (21), 211102 (2011)
  Full Text
• Interrelation between substrate roughness and thin-film structure of functionalized acenes on Graphite.
  Tobias Breuer, Ingo Salzmann, Jan Götzen, Martin Oehzelt, Antonia Morherr, Norbert Koch, Gregor Witte
  Crystal Growth & Design 11 (11), 4996-5001 (2011)
  Full Text