Direct-Write Deposition and Focused-Electron-Beam-Induced Purification of Gold Nanostructures

Abstract

Three-dimensional gold (Au) nanostructures offer promise in nanoplasmonics, biomedical applications, electrochemical sensing and as contacts for carbon-based electronics. Direct-write techniques such as focused-electron-beam-induced deposition (FEBID) can provide such precisely patterned nanostructures. Unfortunately, FEBID Au traditionally suffers from a high nonmetallic content and cannot meet the purity requirements for these applications. Here we report exceptionally pure pristine FEBID Au nanostructures comprising submicrometer-large monocrystalline Au sections. On the basis of high-resolution transmission electron microscopy results and Monte Carlo simulations of electron trajectories in the deposited nanostructures, we propose a curing mechanism that elucidates the observed phenomena. The in situ focused-electron-beam-induced curing mechanism was supported by postdeposition ex situ curing and, in combination with oxygen plasma cleaning, is utilized as a straightforward purification method for planar FEBID structures. This work paves the way for the application of FEBID Au nanostructures in a new generation of biosensors and plasmonic nanodevices.

Purification of Au EBID structures by electron beam post-irradiation under oxygen flux at room temperature

“…Pt EBID structures have been reported to be purified very rapidly (laser exposure time <1 s) by pulsed laser-induced oxidation reaction [16]. In case of Au EBID structures, Beli c et al have developed a protocol to deposited pure Au nanopillars by a in situ electron beam induced curing supported by ex-situ electron beam curing and oxygen plazma cleaning at room temperature [17]. In this paper, we use in situ electron beam post-irradiation under oxygen flux for purification of Au EBID structures.…”

Purified and Crystalline Three-Dimensional Electron-Beam-Induced Deposits: The Successful Case of Cobalt for High-Performance Magnetic Nanowires

“…Diverse approaches have been followed to increase the purity of FEBID deposits, as reviewed by Botman et al in 2009 20 , and further explored since. This includes the growth on substrates at elevated temperatures [26][27][28] , in-situ annealing in high vacuum [29][30][31] , electron beam irradiation 32,33 , exposure to reactive atmospheres 34,35 , laser-assisted heating during deposition 36,37 , post-growth Joule heating upon injection of high electric currents 38 , ex-situ annealing 39,40 , supersonic jet delivery of precursor gas 41 , and combinations of all these methods 35,[42][43][44][45][46] . Astounding success has been achieved in growing virtually-pure Pt deposits by post-growth electron irradiation in oxygen atmosphere 34 , or functional Au plasmonic nanostructures by electron beam irradiation in water vapor atmosphere 13 .…”

Comparison between Focused Electron/Ion Beam-Induced Deposition at Room Temperature and under Cryogenic Conditions

“…In Figure 1, various applications of FEBID and FIBID are sketched: the growth of in-plane and three-dimensional nanostructures on flat substrates [25], as well as on unconventional substrates such as cantilevers/tips [26], and flexible [27], insulating [28] or origami substrates [28], etc. Materials grown by FEBID/FIBID are currently used for circuit edit and mask repair in the semiconductor industry [24,[29][30][31], lamellae preparation [7], the placement of electrical contacts to micro-and nano-structures [32,33], for producing sensors [34,35] and magnetic tips [36][37][38], plasmonic [39][40][41][42] and nano-optical elements [43], superconducting films [44] and nanowires [45], etc. Although FEBID/FIBID is an active field of research and development, a wider impact is hampered by the limited process speed.…”