Contrast mechanisms in secondary electron e-beam induced current (SEEBIC) imaging

TL;DR

SEEBIC imaging in STEM allows direct visualization of sample conductivity by measuring secondary electron currents, offering a new contrast mechanism for electrical characterization of nanostructures like graphene nanoribbons.

Contribution

This paper reviews recent developments in SEEBIC contrast mechanisms and demonstrates its application in characterizing graphene nanoribbon devices.

Findings

SEEBIC provides distinct contrast based on electrical connectivity.

SEEBIC can visualize conductivity variations in nanostructures.

Application to graphene nanoribbons shows practical utility.

Abstract

Over the last few years, a new mode for imaging in the scanning transmission electron microscope (STEM) has gained attention as it permits the direct visualization of sample conductivity and electrical connectivity. When the electron beam (e-beam) is focused on the sample in the STEM, secondary electrons (SEs) are generated. If the sample is conductive and electrically connected to an amplifier, the SE current can be measured as a function of the e-beam position. This scenario is similar to the better-known scanning electron microscopy (SEM)-based technique, electron beam induced current (EBIC) imaging except the signal in STEM is generated by the emission of SEs, hence the name SEEBIC, and in this case the current flows in the opposite direction. Here, we provide a brief review of recent work in this area, examine the various contrast generation mechanisms associated with SEEBIC, and illustrate its use for the characterization of graphene nanoribbon devices.