Diameter modulation of 3D nanostructures in focused electron beam induced deposition using local electric fields and beam defocus

Abstract

Focused Electron Beam Induced Deposition (FEBID) is a leading nanolithography technique in terms of resolution and the capability for three-dimensional (3D) growth of functional nanostructures. However, FEBID still presents some limitations with respect to the precise control of the dimensions of the grown nano-objects as well as its use on insulating substrates. In the present work, we overcome both limitations by employing electrically-biased metal structures patterned on the surface of insulating substrates. Such patterned metal structures serve for charge dissipation and also allow the application of spatially-dependent electric fields. We demonstrate that such electric fields can dramatically change the dimensions of the growing 3D nanostructures 2 by acting on the primary electron beam and the generated secondary electrons. In the performed experiments, the diameter of Pt-C and W-C vertical nanowires grown on quartz, MgO and amorphous SiO2 is tuned by application of moderate voltages (up to 200 V) on the patterned metal microstructures during growth, achieving diameters as small as 50 nm. We identify two competing effects arising from the generated electric fields: a slight change in the primary beam focus point and a strong action on the secondary electrons. Beam defocus is exploited to achieve the in-situ modulation of the diameter of 3D FEBID structures during growth.

Imaging low-dimensional nanostructures by very low voltage scanning electron microscopy: ultra-shallow topography and depth-tunable material contrast

“…This CBS detector provides the most pure topographic contrast, as high-angle BSE emission is practically independent of Z-number. Finally, it is worth mentioning that besides the imaging implications just discussed, sample biasing techniques have also been recently applied in the context of focused electron beam induced deposition (FEBID) in order to improve the control over the dimensions of the growing 3D nanostructures by acting on the primary beam and the generated SE 36 . The general imaging parameters used in this work are the following: LV range acceleration voltage, 2 kV; VLV range acceleration voltage, 2 kV, with BD voltage of 1.5 kV, resulting in an incidence energy of 0.5 keV; current, 0.1 nA; working distance, 2.5 mm; dwell time, 10 μs; scanning mode, integration of 8 lines; image size, 1536 × 1024 pixels.…”

Comparison between Focused Electron/Ion Beam-Induced Deposition at Room Temperature and under Cryogenic Conditions

“…In Figure 1, various applications of FEBID and FIBID are sketched: the growth of in-plane and three-dimensional nanostructures on flat substrates [25], as well as on unconventional substrates such as cantilevers/tips [26], and flexible [27], insulating [28] or origami substrates [28], etc. Materials grown by FEBID/FIBID are currently used for circuit edit and mask repair in the semiconductor industry [24,[29][30][31], lamellae preparation [7], the placement of electrical contacts to micro-and nano-structures [32,33], for producing sensors [34,35] and magnetic tips [36][37][38], plasmonic [39][40][41][42] and nano-optical elements [43], superconducting films [44] and nanowires [45], etc.…”

Focused-Electron-Beam Engineering of 3D Magnetic Nanowires

“…The existence of two growth regimes also stimulates the idea of in situ variation growth conditions to produce 3D nanostructures with modulated diameters [75,76]. This idea could be complemented by other strategies that have been recently proposed for diameter reduction and modulation of 3D nanowires, such as the application of local electric fields or the live control of electron beam focus [77]. In cases where post-growth thermal annealing causes severe shrinkage, other means of purification should be explored further to grant architectural stability.…”