Speaker
Description
Fe(CO)5 is a promising precursor-candidate for ice lithography and a typical precursor for Focused Electron Beam Induced Deposition (FEBID) and Focused Ion Beam Induced Deposition (FIBID) processes. Therefore, its radiolysis has been studied in a plethora of model systems but its solid-phase radiation chemistry has not yet been described in depth.
In the case of isolated molecules, previous gas-phase experiments have shown that radiation-induced breakdown (which ultimately leads to the deposition of a metal layer) occur through the loss CO ligands. Unfortunately, the results obtained in the gas phase cannot be directly transferred to the bulk phase, as numerous other phenomena (e.g., energy transfer between ice and its environment, post-irradiation chemical processes, sputtering, etc.) are also have significance in the latter. In molecular ices irradiation temperature is an important factor which affects the crystal structure of the target, the desorption rates, and the accessibility of certain reaction channels.
In our research, we examined the behavior of Fe(CO)5 ice deposited on ZnSe substrates at temperatures of 20 K and 77 K under 1 MeV proton radiation. These experiments were carried out in the Ice Chamber for Astrophysics / Astrochemistry (ICA) facility, located at the HUN-REN Institute for Nuclear Research in Debrecen, Hungary. This experimental setup allows us to study the irradiation of variety of low-temperature targets with a multitude of different ionic projectiles over a wide energy range. The chemical changes of the targets were followed in situ during the irradiation via Fourier Transformed Infrared spectroscopy, meanwhile the desorbed gases were analyzed by a quadrupole mass spectrometer.
Our experiments showed that CO molecules accumulate in both systems as the result of irradiation. This accumulation was particularly interesting at 77 K, as this temperature is well above the usual desorption temperature of CO. The formation of CO2 was also observed in both systems indicating the secondary fragmentation of the products. At 20 K peaks associated with other oxides containing longer carbon chains also appeared. We observed differences in the relative abundance and formation dynamics of the different radiolysis products as a function of temperature. In both cases, we observed the appearance of absorption bands characteristic of bridging CO molecules as well, indicating the formation of multinuclear iron-carbonyl clusters.
By exploring the effects of temperature, our results could be potentially useful in assessing how Fe(CO)5 could be utilized as a precursor in ice lithography processes.
SUPPORTED BY THE EKÖP-25-3-1-DE-399 UNIVERSITY RESEARCH SCHOLARSHIP PROGRAM OF THE MINISTRY FOR CULTURE AND INNOVATION FROM THE SOURCE OF THE NATIONAL RESEARCH, DEVELOPMENT AND INNOVATION FUND.