Enhanced detection of nanostructures by scanning electron microscopy using insulating materials

• Technique developed to better detect 1D sub-micron structures in scanning electron microscope.
• Insulators in contact with 1D structures created halo-like effect in images.
• 1D structures could be detected at magnifications 50× smaller than usual.
• Technique could be applied to rapidly assay samples for detection of 1D structures.

We report a simple method by which 1D conducting structures with sub-micron diameters can be detected in a scanning electron microscope at magnifications more than an order of magnitude less than would be expected for their size. This enhanced detection was possible under normal operating conditions using a standard secondary electron detector. The technique requires only that the 1D samples must be in good physical contact with an insulating material. Normally, the insulating materials become charged upon electron beam exposure, making them appear relatively bright when imaged by the electron microscope. However, the insulating material appears relatively dark in the vicinity surrounding the conducting 1D structures. This darkened halo can be over 50 times wider than the diameter of the 1D structure itself, making it easy to detect at relatively low magnifications. This dark halo is due to the dissipation of charge from the surface of the conducting material into the conducting nanostructure. Thus, this technique can enable the rapid detection of very small, conducting 1D particles at very low magnification levels, and is simple enough to enable a rapid assaying of samples for the existence of sub-micron 1D structures.