Electron interactions with the heteronuclear carbonyl precursor H2FeRu3(CO)13 and comparison with HFeCo3(CO)12: from fundamental gas phase and surface science studies to focused electron beam induced deposition.

Ragesh Kumar T P,Sven Barth,Helgi Rafn Hrodmarsson,Michael Huth,D Howard Fairbrother,Marc Hanefeld,Paul Weirich,Oddur Ingólfsson,Ragnar Bjornsson,Lukas Hrachowina

doi:10.3762/bjnano.9.53

Abstract

In the current contribution we present a comprehensive study on the heteronuclear carbonyl complex H2FeRu3(CO)13 covering its low energy electron induced fragmentation in the gas phase through dissociative electron attachment (DEA) and dissociative ionization (DI), its decomposition when adsorbed on a surface under controlled ultrahigh vacuum (UHV) conditions and exposed to irradiation with 500 eV electrons, and its performance in focused electron beam induced deposition (FEBID) at room temperature under HV conditions. The performance of this precursor in FEBID is poor, resulting in maximum metal content of 26 atom % under optimized conditions. Furthermore, the Ru/Fe ratio in the FEBID deposit (≈3.5) is higher than the 3:1 ratio predicted. This is somewhat surprising as in recent FEBID studies on a structurally similar bimetallic precursor, HFeCo3(CO)12, metal contents of about 80 atom % is achievable on a routine basis and the deposits are found to maintain the initial Co/Fe ratio. Low temperature (≈213 K) surface science studies on thin films of H2FeRu3(CO)13 demonstrate that electron stimulated decomposition leads to significant CO desorption (average of 8–9 CO groups per molecule) to form partially decarbonylated intermediates. However, once formed these intermediates are largely unaffected by either further electron irradiation or annealing to room temperature, with a predicted metal content similar to what is observed in FEBID. Furthermore, gas phase experiments indicate formation of Fe(CO)4 from H2FeRu3(CO)13 upon low energy electron interaction. This fragment could desorb at room temperature under high vacuum conditions, which may explain the slight increase in the Ru/Fe ratio of deposits in FEBID. With the combination of gas phase experiments, surface science studies and actual FEBID experiments, we can offer new insights into the low energy electron induced decomposition of this precursor and how this is reflected in the relatively poor performance of H2FeRu3(CO)13 as compared to the structurally similar HFeCo3(CO)12.

Highlights

Direct-write technologies using electron beams for nanostructure deposition can surpass the limitations of standard lithography techniques, such as the growth of three-dimensional nanostructures with complex geometries [1,2]
In the current section we discuss decomposition of the heteronuclear complex H2FeRu3(CO)13 through dissociative electron attachment (DEA) and dissociative ionization and we compare the fragmentation patterns observed to our previous work on HFeCo3(CO)12
For HFeCo3(CO)12 [39,40], 23 distinct, identifiable, negative ion fragments are observed in this energy range, along with the intact molecular anion, and for H2FeRu3(CO)13 29 fragments are assigned to discrete molecular compositions

Summary

Introduction

Direct-write technologies using electron beams for nanostructure deposition can surpass the limitations of standard lithography techniques, such as the growth of three-dimensional nanostructures with complex geometries [1,2]. Recent developments demonstrate elegant deposit purification techniques to obtain pure, high quality metals such as Pt and Au by post-growth treatment and in situ injection of water for carbon removal [6,7,8,9,10,11,12,13] These oxidative processes are suitable for precious metals, while other approaches such as annealing under vacuum [14] and hydrogen atmosphere [15,16] are suitable for metals such as Co. alternative precursors for the direct deposition of high-purity compounds are desired especially for non-precious metals and more complex compositions

Results

Discussion

Conclusion