Micro-engineered Nanowire Electron Source for Atomic Resolution Imaging

Abstract

The size tunability and chemical versatility of nanostructures provide attractive engineering potential to realize an electron source of high brightness and spatial temporal coherence, which is a characteristic ever pursued by high resolution electron microscopy. (1–3) Regardless of the intensive research efforts, electron sources that have ever produced atomic resolution images are still limited to the conventional field emitters based on a bulk W needle. It is due to the lack of fabrication precision for nanostructured sources, that is required to align a nanometric emission volume along a macroscopic emitter axis with sub-degree angular deviation. (4) In this work, we produced a LaB6 nanowire electron source which was micro-engineered to ensure a highly collimated electron beam with perfect lateral and angular alignment. Such electron source was validated by installing in an aberration-corrected transmission electron microscope, where atomic resolution in both broad-beam and probe-forming modes were demonstrated at 60kV beam energy. The recorded un-monochromated 0.20eV electron energy loss spectroscopy (EELS) resolution, together with 20% probe forming efficiency and 0.4% probe current peak-to-peak noise ratio under a wide vacuum range, presented the unique advantages of nanotechnology and promised high performance low-cost electron beam instruments.