Role of Low-Energy Electrons (<35 eV) in the Degradation of Fe(CO)5 for Focused Electron Beam Induced Deposition Applications: Study by Electron Stimulated Desorption of Negative and Positive Ions

Abstract

Fe(CO)5 is one of the most common precursors used in focused electron beam induced deposition (FEBID). Since high-energy electrons interacting with matter produce large amounts of secondary electrons with energies <50 eV, those generated within the substrate in FEBID are expected to play a major role in the dissociation process of the precursor molecules. The aim of this study is to identify the role of the secondary electrons in the deposition process of Fe(CO)5 and the relevant dissociation mechanisms, using an electron stimulated desorption system with 4–33 eV electrons. The desorption of charged fragments from thin films of Fe(CO)5, condensed on Xe or onto a Pt foil, was measured as a function of incident electron energy, incident current, and thickness of both Fe(CO)5 and Xe films. Both dissociative electron attachment (DEA) and dipolar dissociation (DD) are involved in the production of anions, specifically, C– and O–, and Fe(CO)x– (x = 0–4). Cations C+, O+, CO+, and Fe(CO)x+ (x = 0–4) were detected with desorption thresholds in the ∼15–25 eV range. These fragments are produced via direct dissociative processes. This study reveals the detailed dissociation mechanisms of Fe(CO)5 induced by low-energy electron impact by the direct observation of Fe(CO)x fragments under different conditions, thus confirming the frequently proposed mechanisms of deposition of Fe by FEBID.