Electron beam irradiation of dimethyl-(acetylacetonate) gold(III) adsorbed onto solid substrates

Abstract

Electron beam induced deposition of organometallic precursors has emerged as an effective and versatile method for creating two-dimensional and three-dimensional metal-containing nanostructures. However, to improve the properties and optimize the chemical composition of nanostructures deposited in this way, the electron stimulated decomposition of the organometallic precursors must be better understood. To address this issue, we have employed an ultrahigh vacuum-surface science approach to study the electron induced reactions of dimethyl-͑acetylacetonate͒ gold͑III͒ ͓Au III ͑acac͒Me 2 ͔ adsorbed onto solid substrates. Using thin molecular films adsorbed onto cooled substrates, surface reactions, reaction kinetics, and gas phase products were studied in the incident energy regime between 40 and 1500 eV using a combination of x-ray photoelectron spectroscopy ͑XPS͒, reflection absorption infrared spectroscopy ͑RAIRS͒, and mass spectrometry ͑MS͒. XPS and RAIRS data indicate that electron irradiation of Au III ͑acac͒Me 2 is accompanied by the reduction in Au III to a metallic Au 0 species embedded in a dehydrogenated carbon matrix, while MS reveals the concomitant evolution of methane, ethane, carbon monoxide, and hydrogen. The electron stimulated decomposition of Au III ͑acac͒Me 2 is first-order with respect to the surface coverage of the organometallic precursor, and exhibits a rate constant that is proportional to the electron flux. At an incident electron energy of 520 eV, the total reaction cross section was Ϸ3.6ϫ 10 −16 cm 2 . As a function of the incident electron energy, the maximum deposition yield was observed at Ϸ175 eV. The structure of discrete Au-containing deposits formed at room temperature by rastering an electron beam across a highly ordered pyrolytic graphite substrate in the presence of a constant partial pressure of Au III ͑acac͒Me 2 was also investigated by atomic force microscopy.

Understanding the electron-stimulated surface reactions of organometallic complexes to enable design of precursors for electron beam-induced deposition

“…However, recent ultra-high vacuum (UHV) surface science studies have begun to provide information useful in formulating design strategies for EBID precursors (see Fig. 3) [31][32][33][34][35][36][37][38]. In contrast to studies conducted in electron microscopes, where deposits are created under steady state deposition conditions, the UHV surface science approach relies on studying the effect of electron irradiation on nanometer thick films of precursor molecules adsorbed onto chemically inert substrates at low temperatures.…”

Unveiling the optical properties of a metamaterial synthesized by electron-beam-induced deposition

“…Thereby, the EBID technique does not only allow for the realization of complex three-dimensional geometries [16,22] but also for depositing them on even nonplanar substrates, if these are at least weakly conductive [10]. During the molecule dissociation, their non-volatile parts form the deposit while the volatile constituents are pumped out [20]. The deposition process depends on the energy and current of the electron-beam, on the dwell time (the time the beam resides at each position) as well as on the scanning raster.…”

Substrate temperature and electron fluence effects on metallic films created by electron beam induced deposition

“…As described previously, a commercial flood gun (Specs FG 15/40) was used as a broad beam electron source. 16,17 Prior to use, the electron gun was thoroughly outgassed and characterized by a Faraday cup to ensure that the sample surface was subjected to a relatively uniform electron fluence. The incident electron energy was calculated from the sum of the electron energy generated by the flood gun (480 eV) and a positive bias (þ20 V) applied to the substrate to attract the secondary electrons emitted during irradiation.…”