Optimization of Pt-C Deposits by Cryo-FIBID: Substantial Growth Rate Increase and Quasi-Metallic Behaviour

Abstract

The Focused Ion Beam Induced Deposition (FIBID) under cryogenic conditions (Cryo-FIBID) technique is based on obtaining a condensed layer of precursor molecules by cooling the substrate below the condensation temperature of the gaseous precursor material. This condensed layer is irradiated with ions according to a desired pattern and, subsequently, the substrate is heated above the precursor condensation temperature, revealing the deposits with the shape of the exposed pattern. In this contribution, the fast growth of Pt-C deposits by Cryo-FIBID is demonstrated. Here, we optimize various parameters of the process in order to obtain deposits with the lowest-possible electrical resistivity. Optimized ~30 nm-thick Pt-C deposits are obtained using ion irradiation area dose of 120 μC/cm2 at 30 kV. This finding represents a substantial increment in the growth rate when it is compared with deposits of the same thickness fabricated by standard FIBID at room temperature (40 times enhancement). The value of the electrical resistivity in optimized deposits (~4 × 104 µΩ cm) is suitable to perform electrical contacts to certain materials. As a proof of concept of the potential applications of this technology, a 100 µm × 100 µm pattern is carried out in only 43 s of ion exposure (area dose of 23 μC/cm2), to be compared with 2.5 h if grown by standard FIBID at room temperature. The ion trajectories and the deposit composition have been simulated using a binary-collision-approximation Monte Carlo code, providing a solid basis for the understanding of the experimental results.

Highly-efficient growth of cobalt nanostructures using focused ion beam induced deposition under cryogenic conditions: application to electrical contacts on graphene, magnetism and hard masking

“…It is also important to mention that Ga doping is below the detection limits of EDS, contrary to what is observed for other precursors materials used in Cryo-FIBID, in agreement with the very low Ga dose required here. 21,23 For these measurements, four deposits of area ~ 400 µm x 400 µm were grown by Cryo-FIBID on a Si substrate under the optimized conditions (ion dose of 15 µC/cm²) and using an ion current of 3 nA (see inset in Fig. 5).…”

“…This can be achieved through cooling the substrate below the precursor condensation temperature. [19][20][21][22][23][24] This Cryo-FIBID approach holds an enormous potential for rapid patterning of metallic micro/nano-deposits. For example, optimized W-C cryo-deposits with a resistivity of 800 •cm were obtained using 50 C/cm 2 Ga + dose and applied as electrical contacts to measure semiconducting nanowires.…”

“…Fig.4: Comparison of different FEBID and FIBID techniques in terms of the optimized dose and its electrical resistivity. The experimental points other than Co Cryo-FIBID have been obtained from references[18,21,23,28,29].…”

Focused Ion Beam Processing for 3D Chiral Photonics Nanostructures

“…A recent upgrade concerns FIB processing under cryogenic conditions, which cause the condensation of the precursor material on the substrate. Cryo-FIBID processes were realized and studied using tungsten [ 62 ] and platinum-based [ 63 ] precursors. The cryogenic temperatures can help to retain the microstructures of sensitive materials when performing milling treatments for electron microscopy [ 64 ].…”

“…The cryogenic temperatures can help to retain the microstructures of sensitive materials when performing milling treatments for electron microscopy [ 64 ]. For FIB induced deposition, the low process temperatures cause an ultrafast growth and, at the same time, reduce the proximity effects and the ion implantations [ 65 ] improving material composition [ 63 ].…”