In situ electron microscopy allows studies of transport of charges and matter in complex structures as well as thermal properties. We can study mechanically and thermally induced changes of charge transport properties using holders designed to enable different stimuli allowing the direct observation and correlation between material structure and properties. The direct correlation between structure and properties on the small scale involving individual interfaces, defects and atoms provides access to new information about which microstructural constituents that are active in determining the material properties on the macro, micro, nano and atomic scale. This talk addresses examples of in situ electrical, mechanical and thermal studies. A few examples are briefly described below.

The nanoscale dimensions of semiconducting nanowires (NWs) provide extended strain relaxation capability between lattice-mismatched materials and enable the fabrication of single-NW p-i-n junction solar cells on low-cost substrates. Due to its sub-wavelength dimension, semiconductor NWs can function as optical antennas and exhibit a “self-concentrating” effect that enhances optical absorption. The strain relaxation capability and the enhanced absorption cross section make NWs potential candidates as highly efficient and low-cost solar cells. Due to the effects of  elastic strain applied on the electronic band structure the strain can be used to achieve NW-based photovoltaic devices with new functionality. We have studied the effect of mechanical strain on the electrical resistance of nanowires. Electron energy loss spectroscopy was used to study the effect of strain on the electronic structure with emphasis on the low energy loss interval of 0 to 50 eV. Electron beam induced current measurements were also performed to study the effect of strain on the diffusion length of the charge carriers [1].

Heating of a transmission electron microscopy (TEM) specimen can be performed in several parallel modes and this talk will address three types of heating modes and show experimental results from nanostructured materials. One mode is by resistive heating of a ring shaped support in contact with the circumference of the entire TEM sample. An additional mode is by use of a heating wire patterned on the TEM sample where the wire is contacted by leads fed through the TEM sample holder. The third mode is by active Joule heating of the nanostructure of study, such as carbon nanotubes, graphene, or metal nanowires. The purpose of having several parallel modes of heating is to enable the separation of temperature dependence, effects of self-Joule heating, effects of radiative heating and thermal transport. It is also important to be able to extract the three dimensional information about the geometry of the investigated structures [2].

1.   L. Zeng, T.K. Nordkvist, P. Krogstrup, W. Jäger and E. Olsson, “Mechanical strain induced nonlinearity of the electrical transport properties of individual GaAs nanowires”, in manuscript.

2.   N. Voskanian and E. Olsson, “Heating holder for in situ three dimensional transmission electron microscopy studies”, in manuscript.

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EMC Abstracts - https://emc-proceedings.com/abstract/in-situ-tem-for-understanding-electrical-and-thermal-transport-properties-on-nano-and-atomic-scales/