Abstract
Electron addition to cobalt tricarbonyl nitrosyl (Co(CO3NO) and its clusters has been explored in helium nanodroplets. Anions were formed by adding electrons with controlled energies, and reaction products were identified by mass spectrometry. Dissociative electron attachment (DEA) to the Co(CO)3NO monomer gave reaction products similar to those reported in earlier gas phase experiments. However, loss of NO was more prevalent than loss of CO, in marked contrast to the gas phase. Since the Co–N bond is significantly stronger than the Co–C bond, this preference for NO loss must be driven by selective reaction dynamics at low temperature. For [Co(CO)3NO]N clusters, the DEA chemistry is similar to that of the monomer, but the anion yields as a function of electron energy show large differences, with the relatively sharp resonances of the monomer being replaced by broad profiles peaking at much higher electron energies. A third experiment involved DEA of Co(CO)3NO on a C60 molecule in an attempt to simulate the effect of a surface. Once again, broad ion yield curves are seen, but CO loss now becomes the most probable reaction channel. The implication of these findings for understanding focused electron beam induced deposition of cobalt is described.
Highlights
Focused electron beam induced deposition (FEBID), which goes by the alternative names of focused electron beam induced processing (FEBIP) or as electron beam induced deposition (EBID), is a promising technique for the direct “writing” of patterns onto solid surfaces.[1−3] It operates at a resolution approaching 1 nm and can be regarded as a variant of chemical vapor deposition in which a focused beam of electrons induces decomposition in a volatile precursor, leading to deposition of the desired material
One problem is the incorporation of nonmetallic impurities into metal deposits, which can arise for several reasons, including incomplete dissociation of the precursor, recombination reactions on the substrate surface, or the electron-induced production of involatile nonmetallic species such as carbon clusters. Another well-known problem is broadening of the deposited structures relative to the diameter of the focused electron beam, a process which is often ascribed to dissociative electron attachment (DEA)
Mechanisms for common FEBID precursor molecules. One such molecule is cobalt tricarbonyl nitrosyl, Co(CO)3NO, which has recently been used as an alternative to Co2(CO)[8] to deposit cobalt using FEBID.[4−6] The deposition of cobalt nanostructures is interesting because of the ferromagnetic properties of this element, which might be exploited in devices such as nanoscale Hall sensors[7,8] and magnetic force microscopy tips.[9]
Summary
Focused electron beam induced deposition (FEBID), which goes by the alternative names of focused electron beam induced processing (FEBIP) or as electron beam induced deposition (EBID), is a promising technique for the direct “writing” of patterns onto solid surfaces.[1−3] It operates at a resolution approaching 1 nm and can be regarded as a variant of chemical vapor deposition in which a focused beam of electrons induces decomposition in a volatile precursor, leading to deposition of the desired material. One such molecule is cobalt tricarbonyl nitrosyl, Co(CO)3NO, which has recently been used as an alternative to Co2(CO)[8] to deposit cobalt using FEBID.[4−6] The deposition of cobalt nanostructures is interesting because of the ferromagnetic properties of this element, which might be exploited in devices such as nanoscale Hall sensors[7,8] and magnetic force microscopy tips.[9] The DEA mechanism for gaseous Co(CO)3NO has recently been explored for the first time by Engmann et al.[10−12] Absolute DEA cross sections were established in this work, and mechanistic information was extracted, including evidence that the first step involves predominantly CO loss Another recent study has investigated the electron-induced decomposition of a nanofilm of Co(CO)3NO on a solid substrate and employed surface science techniques, such as X-ray photoelectron spectroscopy, to extract mechanistic information.[13] As in the gas phase, decomposition on a surface seems to involve facile loss of CO. The electron energy was calibrated using the anion yield data collected by Engmann et al.[10,11] Anion yield curves derived from clusters and from Co(CO)3NO on C60 are referenced to gas phase measurements and are, corrected for the excess energy needed to inject electrons into liquid helium.[18,19] All anion yield curves have been corrected for background counts and isotopic effects of neighboring ions in the mass spectra
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
