Electron-induced surface reactions of (η-CH)Fe(CO)Mn(CO) were explored in situ under ultra-high vacuum conditions using X-ray photoelectron spectroscopy and mass spectrometry. The initial step involves electron-stimulated decomposition of adsorbed (η-CH)Fe(CO)Mn(CO) molecules, accompanied by the desorption of an average of five CO ligands. A comparison with recent gas phase studies suggests that this precursor decomposition step occurs by a dissociative ionization (DI) process. Further electron irradiation decomposes the residual CO groups and (η-CH, Cp) ligand, in the absence of any ligand desorption. The decomposition of CO ligands leads to Mn oxidation, while electron stimulated Cp decomposition causes all of the associated carbon atoms to be retained in the deposit. The lack of any Fe oxidation is ascribed to either the presence of a protective carbonaceous matrix around the Fe atoms created by the decomposition of the Cp ligand, or to desorption of both CO ligands bound to Fe in the initial decomposition step. The selective oxidation of Mn in the absence of any Fe oxidation suggests that the fate of metal atoms in mixed-metal precursors for focused electron beam induced deposition (FEBID) will be sensitive to the nature and number of ligands in the immediate coordination sphere. In related studies, the composition of deposits created from (η-CH)Fe(CO)Mn(CO) under steady state deposition conditions, representative of those used to create nanostructures in electron microscopes, were measured and found to be qualitatively consistent with predictions from the UHV surface science studies.

The Au(I) complexes CF 3 AuCNMe (1a) and CF 3 AuCN t Bu (1b) were investigated as Au(I) precursors for focused electron beam-induced deposition (FEBID) of metallic gold. Both 1a and 1b are sufficiently volatile for sublimation at 125 ± 1 mTorr in the temperature range of roughly 40−50 °C. Electron impact mass spectra of 1a−b show gold-containing ions resulting from fragmenting the CF 3 group and the CNR ligand, whereas in negative chemical ionization of 1a−b, the major fragment results from dealkylation of the CNR ligand. Steady-state depositions from 1a in an Auger spectrometer produce deposits with a similar gold content to the commercial precursor Me 2 Au-(acac) (3) deposited under the same conditions, while the gold content from 1b is less. These results enable us to suggest the likely fate of the CF 3 and CNR ligands during FEBID.

The ability of electrons and atomic hydrogen (AH) to remove residual chlorine from PtCl2 deposits created from cis-Pt(CO)2Cl2 by focused electron beam induced deposition (FEBID) is evaluated. Auger electron spectroscopy (AES) and energy-dispersive X-ray spectroscopy (EDS) measurements as well as thermodynamics calculations support the idea that electrons can remove chlorine from PtCl2 structures via an electron-stimulated desorption (ESD) process. It was found that the effectiveness of electrons to purify deposits greater than a few nanometers in height is compromised by the limited escape depth of the chloride ions generated in the purification step. In contrast, chlorine atoms can be efficiently and completely removed from PtCl2 deposits using AH, regardless of the thickness of the deposit. Although AH was found to be extremely effective at chemically purifying PtCl2 deposits, its viability as a FEBID purification strategy is compromised by the mobility of transient Pt–H species formed during the purification process. Scanning electron microscopy data show that this results in the formation of porous structures and can even cause the deposit to lose structural integrity. However, this phenomenon suggests that the use of AH may be a useful strategy to create high surface area Pt catalysts and may reverse the effects of sintering. In marked contrast to the effect observed with AH, densification of the structure was observed during the postdeposition purification of PtCx deposits created from MeCpPtMe3 using atomic oxygen (AO), although the limited penetration depth of AO restricts its effectiveness as a purification strategy to relatively small nanostructures.

Monolayer-protected gold nanoparticles (AuNPs) with average diameters of 2-4 nm have been covalently attached to zinc oxide nanorods using dithiol ligands. Electron microscopy and Raman spectroscopy show that ozone treatment or annealing at 300 or 450 °C increases the average diameter of the AuNPs to 6, 8, and 14 (±1) nm, respectively, and decomposes the organic layers to various degrees. These treatments locate the AuNPs closer to the nanorods. Heating and subsequent ozone exposure changes the color of the as-prepared nanocomposite powder from blue to purple due to oxidation of the outer layer of the AuNPs, and heating to 300 °C changes it to pink due to oxygen desorption. ZnO nanorods have a bimodal photoluminescence spectrum that consists of an ultraviolet excitonic peak and a visible, surface defect-related peak. Ozone treatment and annealing of the nanocomposite decreases the intensities of both peaks due to quenching by the AuNPs, but the visible peak is affected less. The photocatalytic efficiency of the nanocomposites toward oxidative degradation of rhodamine B has been measured and follows the order 300 °C > 450 °C > ozone treated ≈ as-prepared ≈ bare ZnO. The greater efficiency of the annealed samples likely arises from decreased electron-hole pair recombination rates.

The use of bimetallic precursors in focused electron beam induced deposition (FEBID) allows mixed metal nanostructures with well-defined metal ratios to be generated in a single step process. HFeCo 3 (CO) 12 is an example of one such bimetallic precursor that has previously been shown to form deposits with unusually high metal content (>80%) as compared to that of typical FEBID deposits (<30% metal content). To better understand the elementary bond breaking steps involved in FEBID of HFeCo 3 (CO) 12 , we have employed a UHV surface science approach to study the effect of electron irradiation on nanometer thick films of HFeCo 3 (CO) 12 molecules. Using a combination of in situ Xray photoelectron spectroscopy and mass spectrometry, we observed that the initial step of electron induced HFeCo 3 (CO) 12 dissociation is accompanied by desorption of ∼75% of the CO ligands from the precursor. A comparison with recent gas phase studies of HFeCo 3 (CO) 12 indicates that this process is consistent with a dissociative ionization process, mediated by the secondary electrons produced by interaction of the primary beam with the substrate. The loss of CO ligands from HFeCo 3 (CO) 12 in the initial dissociation step creates partially decarbonylated intermediates, HFeCo 3 (CO) x (x avg. ≈ 3). During a typical FEBID process, further electron exposure or thermal reactions can further transform these intermediates. In our UHV surface science approach, the effect of these two processes can be studied in isolation and identified. Under the influence of further electron irradiation, XPS data reveals that the remaining CO ligands in the partially decarbonylated intermediates decompose to form residual carbon and iron oxides, suggesting that those CO ligands that desorbed in the initial step are lost predominantly from the Co atoms. However, annealing experiments demonstrate that CO ligands in the partially decarbonylated intermediates desorb under vacuum conditions at room temperature, leaving behind films that are free of almost any carbon or oxygen contaminants. This combination of efficient CO desorption during the initial dissociation step, followed by thermal CO desorption from the partially decarbonylated HFeCo 3 (CO) x (x avg. ≈ 3) intermediates provide a rationale for the high metal contents observed in FEBID nanostructures created from HFeCo 3 (CO) 12 .