Cryo-Focused Ion Beam-Induced Deposition of Tungsten–Carbon Nanostructures Using a Thermoelectric Plate

Abstract

Focused Ion Beam-Induced Deposition (FIBID) is a single-step nanopatterning technique that applies a focused beam of ions to induce the decomposition of a gaseous precursor. The processing rate of FIBID increases by two orders of magnitude when the process is performed at cryogenic temperatures (Cryo-FIBID): the precursor forms a condensed layer on the surface of the cooled substrate, greatly enhancing the amount of material available for decomposition. Cryo-FIBID has been achieved so far by making use of liquid nitrogen-based cooling circuits, which require the passage of a flowing gas as a cooling agent. Here, the Cryo-FIBID of the W(CO)6 precursor is performed using a coolant-free thermoelectric plate utilizing the Peltier effect. Performed at −60 ∘C, the procedure yields a W–C-based material with structural and electrical properties comparable to those of its counterpart grown in coolant-based Cryo-FIBID. The use of the thermoelectric plate significantly reduces the vibrations and sample drift induced by the flow of passing coolant gas and allows for the fabrication of similar nanostructures. In summary, the reported process represents a further step towards the practical implementation of the Cryo-FIBID technique, and it will facilitate its use by a broader research community.

Reactions of Ions with Adsorbed Me3PtCpMe: The Role of Ion Identity

“…Structures are created by IBID in a constant partial pressure of precursor molecules where all of the elementary reaction steps are occurring simultaneously. ,,− Thus, adsorbed Me 3 PtCpMe molecules are undergoing decomposition into nonvolatile species, while deposited atoms at the growth surface are simultaneously being subjected to the effects of ion bombardment. In contrast, the UHV surface science approach allows us to independently study two of these elementary steps; (i) ion–adsorbate interactions that contribute to the conversion of volatile precursor molecules into nonvolatile deposited atoms and (ii) subsequent postdeposition processing that occurs in the form of sputtering.…”

Ice lithography using tungsten hexacarbonyl

“…Hence, for applications requiring smooth surface finishing, the exposure dose should be slightly below the critical dose, and low primary electron energy is preferred. The critical dose to cross-link W(CO) 6 is 50 μC/cm 2 for cryo-FIBID using Ga + [11] and this is because ions are much more efficient in generating secondary electrons needed for chemical cross-linking.…”

“…IL advantages are discussed in detail in the references, and we highlight three advantages; (i) IL enables the processing of very fragile samples such as suspended carbon nanotubes [2], (ii) layer-by-layer processing for 2.5 D lithography [4,8], (iii) IL is 4 orders of magnitude faster than focused electron beam induced deposition (FEBID) [8]. Faster process is confirmed by De Teresa and colleagues, that showed speed of organometallic ices cross-linking using ion-beams (cryo-FIBID) increases by several orders of magnitude compared with gas-based processes [11,12]. Since the IL process uses electron and solid interaction, it is 1000 times faster than the FEBID, which is based on electron-gassubstrate interactions [9].…”

“…1b), which is an inexpensive and well-characterized metalorganic precursor. We selected the tungsten hexacarbonyl precursor because it has been studied by both FEBID [14][15][16] and Cryo-FIBID [11], and we could compare different methods. Dose optimization was performed for area-and line-patterning, followed by X-ray photoelectron spectroscopy (XPS) characterization of chemical components and the demonstration of IL tungsten as a mask for silicon etching.…”

Special Issue on Nanoscale Assembly and Integration for Applications

“…Ohta et al [2] describe the fabrication and properties of nanocrystalline ZnTe thin films and nanowire arrays for applications in electronics and photovoltaics. Orus et al [3] present results for the focused ion beam-induced deposition of nanowire patterns that utilize a cooling thermoelectric plate to reduce the processing time during the nanofabrication of nanostructures and devices. Sapkota et al [4] present the use of planetary ball-milled ZnO nanoparticle inks for the creation of inexpensive thin film gas sensors that operate at room temperature and can detect different target species including hydrogen and methane.…”