Low-resistivity, high-resolution W-C electrical contacts fabricated by direct-write focused electron beam induced deposition

Abstract

Background: The use of a focused ion beam to decompose a precursor gas and produce a metallic deposit is a widespread nanolithographic technique named focused ion beam induced deposition (FIBID). However, such an approach is unsuitable if the sample under study is sensitive to the somewhat aggressive exposure to the ion beam, which induces the effects of surface amorphization, local milling, and ion implantation, among others. An alternative strategy is that of focused electron beam induced deposition (FEBID), which makes use of a focused electron beam instead, and in general yields deposits with much lower metallic content than their FIBID counterparts. Methods: In this work, we optimize the deposition of tungsten-carbon (W-C) nanowires by FEBID to be used as electrical contacts by assessing the impact of the deposition parameters during growth, evaluating their chemical composition, and investigating their electrical response. Results: Under the optimized irradiation conditions, the samples exhibit a metallic content high enough for them to be utilized for this purpose, showing a room-temperature resistivity of 550 μΩ cm and maintaining their conducting properties down to 2 K. The lateral resolution of such FEBID W-C metallic nanowires is 45 nm. Conclusions: The presented optimized procedure may prove a valuable tool for the fabrication of contacts on samples where the FIBID approach is not advised

Focused Electron Beam Micro- and Nanopatterning of Thin Films Derived from Sol–Gels Based on TiO2 Precursors for Planar Photonics

“…The alternative is to apply condensed phase precursors, such as sol−gel materials, for FEB direct writing. 12−17 This approach has several advantages over the gas-phase FEBID, such as much higher precursor densities, resulting in usually lower electron doses needed for obtaining desired deposits (typically about 1−100 mC/cm 2 for condensed phase 14,16−19 versus above 1 C/cm 2 for gas phase 18,20,21 ), simpler and less expensive ways of delivering precursors to substrates (i.e., spin-coating or dipcoating), and flexibility in tuning compositions of materials. However, there have been few reports on studies aimed at obtaining TiO 2 structures using e-beam direct writing of sol− gel-derived layers so far.…”

“…The fabrication of TiO 2 structures by FEB-induced deposition (FEBID) using gas-phase precursors has been reported by different research groups. − High-purity (i.e., carbon-free) titanium oxide structures can be produced with the FEBID, but this method has two main disadvantages, namely, the low deposition rates and the necessity of using special gas injection systems (GIS) for delivering precursors to substrates. The alternative is to apply condensed phase precursors, such as sol–gel materials, for FEB direct writing. − This approach has several advantages over the gas-phase FEBID, such as much higher precursor densities, resulting in usually lower electron doses needed for obtaining desired deposits (typically about 1–100 mC/cm 2 for condensed phase ,− versus above 1 C/cm 2 for gas phase ,, ), simpler and less expensive ways of delivering precursors to substrates (i.e., spin-coating or dip-coating), and flexibility in tuning compositions of materials. However, there have been few reports on studies aimed at obtaining TiO 2 structures using e-beam direct writing of sol–gel-derived layers so far. , …”