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New Method at PGI

Determining the Atomic Structure and Electronic Transport Properties of Individual Nanoelectronic Components

August 21, 2012

Electronic components are becoming steadily smaller and at the same time packed ever-more densely onto computer chips.  As a result, more and more components are being crammed onto an increasingly smaller surface area.  Conventional silicon-based semiconductor technology will, in the process, soon reach its physical limits.  New concepts, based perhaps on semiconductor nanowires, could contribute towards making further miniaturization possible.  However, such components are so small that even the slightest variation in their atomic structure could radically alter their electronic transport properties.  For this reason, it would be particularly advantageous to be able to determine the atomic structure of individual components.                             

Dr. Carola Meyer and her group at the division of Electronic Properties (PGI-6), together with Dr. Stefan Trellenkamp (Process Technology, PGI-8-PT), have done just that, and developed an electron lithography process for Si3N4 membranes suitable for use in transmission electron microscopy (TEM).  Structures can thus be produced on the membranes, through which the components can be contacted electrically.  “This allows us to measure both the electrical transport properties and the atomic structure of the same components,” explains Robert Frielinghaus, who is working on the project as part of his Ph.D. thesis.  “In addition, interaction with the substrate is avoided as the semiconductor nanowires being examined are suspended freely between the contacts”.  

  

2012-08-21-APL_PGI-newsScanning electron micrograph of an electrically contacted nanowire (diameter 110 nm) with a schematic of the electrical measurement configuration. The marked middle section was measured using TEM. The scale bar is 1 µm.
Copyright: Forschungszentrum Jülich

 

The figure shows an electrically contacted InAs nanowire (shown in black) on a structured TEM membrane (yellow).  Together with Prof. Thomas Schäpers of the division Semiconductor Nanoelectronics (PGI-9) who has studied the properties of these wires for quite some time, Frielinghaus and Meyer investigated the correlation between quantum fluctuations in transport, known as the “universal conductance fluctuations” and the change in the wurtzite and zincblende structure of the atomic lattice.  Schäpers is excited about the results:  “Never before have I seen such accurate measurements of these systems!”  Apart from the scientists in Jülich, other groups from RWTH Aachen also collaborated in this project, which is where the TEM images were recorded.

The editors and referees of the journal “Applied Physics Letters” agreed that this combination of methods was indeed noteworthy, and published the results in the current issue:

 

Monitoring structural influences on quantum transport in InAs nanowires
Frielinghaus et al.;
Appl. Phys. Lett. 101, 062104 (2012)

 

Website of PGI-6 Electronic Properties:
http://www.fz-juelich.de/pgi/pgi-6/EN/Home/home_node.html

Website of PGI-8 Biolelectronics:
http://www.fz-juelich.de/pgi/pgi-8/EN/Home/home_node.html

Website of PGI-9 Semiconductor Nanoelectronics:
http://www.fz-juelich.de/pgi/pgi-9/EN/Home/home_node.html


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