Selective functionalization of tailored nanostructures

Rapid Electron Beam Writing of Topologically Complex 3D Nanostructures Using Liquid Phase Precursor

Advancement of focused electron beam-induced deposition (FEBID) as a versatile direct-write additive nanoscale fabrication technique has been inhibited by poor throughput, limited choice of precursors, and restrictions on possible 3D topologies. Here, we demonstrate FEBID using nanoelectrospray liquid precursor injection to grow carbon and pure metal nanostructures via direct decomposition and electrochemical reduction of the relevant precursors, achieving growth rates 10(5) times greater than those observed in standard gas-phase FEBID. Initiating growth at the free surface of a liquid pool enables fabrication of complex 3D carbon nanostructures with strong adhesion to the substrate. Deposition of silver microstructures at similar growth rates is also demonstrated as a promising avenue for future development of the technique.

Direct-write deposition and focused-electron-beam-induced purification of gold nanostructures

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.

Gold complexes for focused-electron-beam-induced deposition

Four gold complexes were tested as a precursor for focused-electron-beam-induced deposition: [ClAu(III)Me2]2, ClAu(I)(SMe2), ClAu(I)(PMe3), and MeAu(I)(PMe3). Complexes [ClAu(III)Me2]2 and MeAu(I)(PMe3) are volatile, have sufficient vapor pressure at room temperature for deposition experiments, and were found to yield deposits that contain gold (29-41 and 19-25 atom %, respectively). Electrons easily remove the Cl ligand from [ClAu(III)Me2]2, and predominantly both methyl ligands are incorporated into the deposit. Electrons remove at least one methyl group from MeAu(I)(PMe3). Complexes ClAu(I)(SMe2) and ClAu(I)(PMe3) are not suitable as a precursor. They dissociate in vacuum, and the only volatile components are Cl, SMe2, and PMe3, respectively.

Enhanced by-product desorption via laser assisted electron beam induced deposition of W(CO)6 with improved conductivity and resolution

Nanowires with higher tungsten (W) concentration and enhanced conductivity were grown via the laser assisted electron beam induced deposition (LAEBID) technique using tungsten hexacarbonyl W(CO)6 as the gas precursor. Periodic, pulsed laser irradiation facilitated CO desorption during growth by heating the deposit. Deposit purity improved with laser pulse width up to the threshold for pyrolytic laser chemical vapor deposition (LCVD). Higher resolution was also observed and was attributed to reduced CO incorporation and higher deposit density. The optimal composition and lowest resistivity was achieved by synchronizing the electron beam induced deposition and laser assist such that (1) the electron beam induced deposit is less than a monolayer per cycle and (2) the laser induced heating is just below the LCVD threshold.