Scanning probe and tunnel microscopy

Scanning probe microscopy belongs to the most important methods in the field of nanoanalytics. Scanning probe methods are based on a local reciprocation between a surface and a scanning probe tip, which is brought very near (in atomic dimensions) to the surface of the sample. The measuring procedure can be compared in principle with a miniaturized record player, where a tip moves over a surface, scans it on an atomic scale and converts the signals into an image. The received information can concern for example the chemical composition of the surface, the distribution of surface potentials, magnetic or electrical fields. The development of miniaturized, automated scanning probe devices for space missions, offers the possibility of characterizing solids and dust particles in space with nanoscale resolution without a sample transport to earth. A concrete example is the use for the investigation of soil and dust particles on the Mars surface. An appropriate AFM device was developed by a Swiss consortium for the Mars Surveyor mission of NASA (Gautsch 2000). To increase the dependability of the system, eight microprobes were installed on the AFM chip, although however just one cantilever is used for the measurements (see illustration 19).

The microelectronic components of the AFM equipment have been adapted to the extreme space conditions (vibrations, temperature gradients, radiation etc.). Due to the cancelling of the Mars Lander mission in the frame of the Mars Surveyor 2001 mission of NASA, the equipment was not in operation yet.

The LMU Munich (working group of Professor Heckl) developed a high resolution scanning tunnel microscope (STM) for applications in space, which was already tested in parabolic flights and at present is prepared for employment on the ISS. The microscope is intended to investigate the growth of defective-free DNA crystals under microgravity with nanosca-le resolution.59

Miniaturized scanning probe microscope for space missions

Illustration 19: AFM-Chip with 8 cantilever probes for the investigation of soil and dust particles on the MARS surface (Quelle: Uni Basel)

http://monet.physik.unibas. ch/famars/index.htm

59 IDW press release from 5.12.2001: ‚ÄěPremiere: test of a scanning tunnelling microscope under microgravity", (http://idw-online.de)

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