New Directions in Focused Ion Beam Induced Deposition for the Nanoprinting of Functional 3D Heterostructures

TL;DR

This work expands focused ion beam induced deposition (FIBID) into true 3D nanoprinting by leveraging helium and neon ion beams to write complex multimaterial nanostructures. It demonstrates sequential deposition of metallic and insulating layers to form heterostructures, and uses in-situ milling to sculpt nanoscale geometries such as nanopillars, nanorings, and capped/nanosleeves. Advanced electron microscopy reveals that deposit composition and crystallinity depend on ion mass (e.g., $^{22}$Ne/$^{20}$Ne isotopes) and precursor chemistry, including polycrystalline tungsten from He-FIBID and amorphous PMCPS. Ion implantation drives subsurface voids and hollow cores, enabling nanocontainers and porous metamaterials, with SRIM confirming implantation-depth profiles; collectively, these results position He/Ne-FIBID as a versatile platform for next-generation nanoscale devices.

Abstract

The focused ion beam (FIB) microscope is well established as a high-resolution machining instrument capable of site-selectively removing material down to the nanoscale. Beyond subtractive processing, however, the FIB can also add material using a technique known as focused ion beam induced deposition (FIBID), enabling the direct-write of complex nanostructures. This work explores new directions in three-dimensional nanoprinting with FIBID, harnessing unique features of helium and neon FIBs to fabricate nanoscale heterostructures, including multimaterial architectures and deposits with engineered internal voids. Detailed insight into the chemical and structural composition of these nanostructures is obtained using advanced electron microscopy, revealing buried interfaces and material transformations. Building on these results, the evolution of FIBID into a versatile platform for functional nanomaterials design is discussed, opening pathways toward next-generation nanoscale devices and technologies.

Figures (5)

• Figure 1: Examples of nanostructure arrays and individual heterostructures fabricated by He-FIBID using different precursor chemistries. (a) 54$^\circ$ tilt view HIM image of a periodic height-modulated array of metallic nanopillars. (b)(i) Plan view HIM image of an array of insulating nanorings, (ii) 40$^\circ$ tilt view HIM image of a portion of the array, (iii) and (iv) TEM side views of nanorings/nanosleeves grown to different heights. (c) TEM image of a vertically stacked metallic-insulator-metallic heterostructure, the sidewalls of which were trimmed using Ne-FIB milling after the deposition. (d)(i) TEM image of a metallic nanopillar capped with insulator, (ii) high-magnification view of the tip region. (e)(i) STEM image of a metallic nanopillar inside a shorter insulating nanosleeve, (ii) nanopillar and nanosleeve of similar heights, (iii) insulating nanopillar inside a metallic nanosleeve.
• Figure 2: Elemental composition and grain size analysis of metallic deposits. (a) Relative amounts (at.%) of W, C and O in nanostructures fabricated by He-, Ne- and Ga-FIBID from the W(CO)$_6$ precursor, determined by STEM-XEDS. (b)(i) STEM image of a nanopillar fabricated by He-FIBID from the same precursor, (ii) mean diffraction pattern computed from 4D-STEM scan of the tip apex region highlighted in the adjacent STEM image, (iii) grain map obtained following automated Bragg disk detection and non-negative matrix factorization of the 4D-STEM dataset.
• Figure 3: Metallic nanopillar fabricated by Ne-FIBID with satellite deposition due to $^{22}$Ne isotope on one side, imaged here by HIM under a tilt of 54$^\circ$.
• Figure 4: High-resolution TEM image of a portion of a metallic nanopillar fabricated by He-FIBID revealing a hollow core (highlighted by the blue cylinder) due to concurrent milling by the tightly focused He ion beam. This phenomenon was first reported in Kohama2013.
• Figure 5: Nanostructures with internal voids created by ion implantation during He-FIBID and Ne-FIBID at higher doses. (a)(i) STEM image of a metallic nanopillar fabricated by Ne-FIBID with porosity introduced by Ne implantation, (ii) simulated 2D depth distribution for 25keV Ne ions incident on the W-C-O deposit material. (b)(i) STEM image of an insulating deposit fabricated by He-FIBID with internal void due to He implantation, (ii) simulated 2D depth distribution for 25keV He ions incident on the Si-C-O deposit material.