Event calendar file
Department of Nuclear and Atomic Physics Seminars
The role of low energy secondary electrons in focused Electron beam induced deposition (FEBID)
by Prof. Oddur Ingolfsson (University of Iceland, Iceland)
Thursday, November 1, 2012
from
to
(Asia/Kolkata)
| Description |
Focused Electron Beam Induced Deposition (FEBID) is a very promising method for the deposition of metallic and non-metallic functional nanoscopic structures. In this approach a tightly focused high-energy electron beam, typically from a scanning electron microscope (SEM) is used to decompose adsorbed precursor molecules such as metal complexes, and ideally a pure deposit is generated on the surface while dissociated volatile ligand molecules are pumped away. Currently the main challenges in further advancing FEBID as an industrial processing tool is to achieve better control of the composition and the purity of the deposits, and to further improve the spatial resolution (currently routinely around 10 nm). While contamination of the deposit is mainly attributed to incomplete decomposition of precursor molecules, co-deposition of ligands, and contamination from residual gases, broadening of the structures is generally attributed to electron flux outside the focus point of the primary beam. These effects are, in turn, mainly ascribed to low energy secondary electrons (SE) and ackscattered electrons (BSE) that are produced through elastic and inelastic scattering of the primary beam. The SEs are generally abundant (also outside the focal point of the primary beam) and their energy distribution peaks well below10 eV. In this energy range the only efficient fragmentation mechanism is dissociative electron attachment (DEA). This is a resonant process that can be very efficient and causes mainly incomplete dissociation, and may thus potentially contribute significantly to the deposition of non-metal contaminants. Dissociative ionization (DI), on the other hand, is a non-resonant process, but can nonetheless be very effective at fairly low incident energies (10–50 eV). It may thus also contribute significantly to adverse effects in FEBID, especially to broadening of the deposit. In an attempt to give some insight into the dissociation mechanisms relevant to FEBID, gas phase DEA and DI results on typical FEBID precursors are compared and brought into context with earlier surface science studies on decomposition of the same molecules when these are adsorbed on a substrate and exposed to high energy electrons. |
| Organised by | Dr. Vaibhav Prabhudesai |
