In Situ TEM Characterization of Semiconductor Nanowires

This article outlines how in situ biasing TEM was employed to investigate the electrical features of InAs nanowires (NWs).

A breakdown of NW happens in close proximity to the cathode side as the electrical current increases. Dynamical changes were observed in real life with simultaneous I – V measurements.

Purpose

  • Fabricate low ohmic contacts to the InAs NW
  • Driving force: Possible application of InAs semiconductor NW’s in high-performance electronic devices
  • Live observation of the breakdown of the NW with electrical characterization occuring at the same time
  • Characterize the electrical features of InAs NWs with the exclusion of experimental artefacts

Challenges

  • Electrical measurements making contact utilizing scanning tunneling microscopy can lead to the following limitations:
    1. Strong heating of the NW
    2. Incorrect values for the I-V properties
  • High resolution imaging of the initial breakdown position.

(a) – (c) I–V curves versus time of InAs NW throughout the entire process. (d) – (k) The corresponding TEM images at particular points are illustrated in (a) and (b).

Figure 1. (a) – (c) I–V curves versus time of InAs NW throughout the entire process. (d) – (k) The corresponding TEM images at particular points are illustrated in (a) and (b).

(a) HAADF image of the InAs NW post-breakdown, indium particles noticed close to the anode, while the breakdown occurred near to the cathode. (b) – (d) EDX maps of the InAs NW.

Figure 2. (a) HAADF image of the InAs NW post-breakdown, indium particles noticed close to the anode, while the breakdown occurred near to the cathode. (b) – (d) EDX maps of the InAs NW.

Results

In this example, through the process of in situ biasing TEM, a breakdown process of InAs NWs was monitored while I-V properties were recorded (Figure 1).

From Figure 1 (d) – (k) it is apparent that the breakdown does not happen at the center of the NWs, which may be predictable due to the fact that two equal electrodes on each side and Joule heating NW should be the hottest in the middle.

The breakdown happens much nearer to the cathode. Before the breakdown, the sphere-like particles seem to be near to the anode side, which increase in number and size (Figure 1 (j) – (k)).

It was verified through the use of EDX that these particles are rich in indium (Figure 2 (b)), while the broken area is rich in arsenic (Figure 2 (c)). It was suggested that the breakdown mechanism is established on the electromigration of In, resulting in NW breakage close to the cathode side.

It was demonstrated through the use of MEMS based Nano-Chips in this experiment that it was possible to mitigate NWs strong heating as a result of Joule heating created by high-resistance contacts.

Electrical measurements with simultaneous TEM imaging verified that the breakdown of the NW happens at the cathode side when the current is increased. It was proposed that an electromigration mechanism and Joule heating should be used for the breakdown procedure.

References and Further Reading

  • Zhang, Chao, et al. “In situ electrical characterization of tapered InAs nanowires in a transmission electron microscope with ohmic contacts.” Nanotechnology 26.15, 15570 (2015).

This information has been sourced, reviewed and adapted from materials provided by DENSsolutions.

For more information on this source, please visit DENSsolutions.

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