Structural properties and formation mechanism of nanostructures induced by electron beam irradiation

Abstract

Potential applications of nanoparticles in next-generation electronic and optoelectronic devices have driven extensive efforts to control precisely the sizes and the shapes of the nanoparticles by using methods such as oxidation, wet etching, laser ablation, thermal annealing, focused ion-beam processing, electron beam irradiation, and selective chemical reaction. Even though some studies concerning randomly distributed nanoparticles are formed by using several techniques, relatively few studies on the local formation of the sub 10 nm nanoparticles have been done. The widely used resist-based electron beam lithography techniques are limited down to tens of nanometers and top-down fabrication of sub-10 nm scale devices with high reproducibility and yield is generally still challenging. The ability to efficiently fabricate high-quality nanostructure is important because many physical, chemical, and biological properties of diverse systems depend on electron motion, fluid motion, and/or chemical reactions that occur at nanometer scales. For instance, electrons typically travel a few nanometers at room temperature before scattering inelastically in metals or flipping their spin in ferromagnetic metals and their transition into the superconducting phase becomes sensitive to size at $\sim 10 nm$. This paper presents data for the formation mechanism and microstructural properties of locally distributed sub 10 nm of nanostructure by using a focused electron beam irradiation in a direct visual control equipment. Transmission electron microscopy (TEM) measurements were carried out to investigate the microstructural characteristics of nanostructures. Energy dispersive spectroscopy (EDS) measurements were performed to investigate change of the stoichiometry of nanostructures. Formation mechanisms are described on the basis of the high-resolution TEM (HRTEM) images and the EDS profiles.