Beam Induced Deposition Technique Research Articles

Atom-by-Atom Direct Writing.

Direct-write processes enable the alteration or deposition of materials in a continuous, directable, sequential fashion. In this work, we demonstrate an electron beam direct-write process in an aberration-corrected scanning transmission electron microscope. This process has several fundamental differences from conventional electron-beam-induced deposition techniques, where the electron beam dissociates precursor gases into chemically reactive products that bond to a substrate. Here, we use elemental tin (Sn) as a precursor and employ a different mechanism to facilitate deposition. The atomic-sized electron beam is used to generate chemically reactive point defects at desired locations in a graphene substrate. Temperature control of the sample is used to enable the precursor atoms to migrate across the surface and bond to the defect sites, thereby enabling atom-by-atom direct writing.

Direct-write of tungsten-carbide nanoSQUIDs based on focused ion beam induced deposition.

NanoSQUIDs are quantum sensors that excel in detecting a small change in magnetic flux with high sensitivity and high spatial resolution. Here, we employ resist-free direct-write Ga+ Focused Ion Beam Induced Deposition (FIBID) techniques to grow W-C nanoSQUIDs, and we investigate their electrical response to changes in the magnetic flux. Remarkably, FIBID allows the fast (3 min) growth of 700 nm × 300 nm nanoSQUIDs based on narrow nanobridges (50 nm wide) that act as Josephson junctions. Albeit the SQUIDs exhibit a comparatively low modulation depth and obtain a high inductance, the observed transfer coefficient (output voltage to magnetic flux change) is comparable to other SQUIDs (up to 1300 μV/Φ 0), which correlates with the high resistivity of W-C in the normal state. We discuss here the potential of this approach to reduce the active area of the nanoSQUIDs to gain spatial resolution as well as their integration on cantilevers for scanning-SQUID applications.

Electron and X-ray Focused Beam-Induced Cross-Linking in Liquids: Toward Rapid Continuous 3D Nanoprinting and Interfacing using Soft Materials.

Multiphoton polymer cross-linking evolves as the core process behind high-resolution additive microfabrication with soft materials for implantable/wearable electronics, tissue engineering, microrobotics, biosensing, drug delivery, etc. Electrons and soft X-rays, in principle, can offer even higher resolution and printing rates. However, these powerful lithographic tools are difficult to apply to vacuum incompatible liquid precursor solutions used in continuous additive fabrication. In this work, using biocompatible hydrogel as a model soft material, we demonstrate high-resolution in-liquid polymer cross-linking using scanning electron and X-ray microscopes. The approach augments the existing solid-state electron/X-ray lithography and beam-induced deposition techniques with a wider class of possible chemical reactions, precursors, and functionalities. We discuss the focused beam cross-linking mechanism, the factors affecting the ultimate feature size, and layer-by-layer printing possibilities. The potential of this technology is demonstrated on a few practically important applications such as in-liquid encapsulation of nanoparticles for plasmonic sensing and interfacing of viable cells with hydrogel electrodes.

Biomimetics: Nature Helps: Toward Bioinspired Bactericidal Nanopatterns (Adv. Mater. Interfaces 16/2019)

Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacterial cells are killed upon contact with surface nanopatterns with precisely controlled dimensions and arrangement, produced by electron beam-induced deposition (EBID) technique. The main cause of such bactericidal effect is the cell wall being stretched and mechanically ruptured as the bacteria contact the nanopatterns. Further details can be found in article number 1900640 by Mahya Ganjian, Khashayar Modaresifar, and co-workers.

Domain nucleation behavior in ferroelectric films with thin and ultrathin top electrodes versus insulating top layers

The effect of varying the thickness of Pt top electrodes made by the electron beam induced deposition technique on the domain nucleation characteristics of Pb(Zr,Ti)O3 films has been investigated by piezoresponse force microscopy. The advantage of this experimental setup is that the nucleation position can be precisely controlled allowing comparison between two capacitor structures with different top electrode thicknesses and negating the role of defect-induced polarization switching scenarios. In the ultrathin limit (<5nm), the coercive biases of polarization switching change substantially relative to thicker electrodes, from −4.6 to −2.6V and from +3.5 to 5.5V respectively, which we link to a work function size effect. The evolution of the piezoresponse and coercive biases as a function of hysteresis loop cycling is presented and contrasted with that obtained on the bare film surface with no top electrode. To provide a counterpoint to the observed effects with top electrodes, we have demonstrated the variation in switching due to a top silicon oxide insulating layer. This work has revealed a method which could be used to control nucleation bias in ferroelectric thin film systems.

All‐Carbon Electrode Molecular Electronic Devices Based on Langmuir–Blodgett Monolayers

Nascent molecular electronic devices, based on monolayer Langmuir-Blodgett films sandwiched between two carbonaceous electrodes, have been prepared. Tightly packed monolayers of 4-((4-((4-ethynylphenyl)ethynyl)phenyl)ethynyl)benzoic acid are deposited onto a highly oriented pyrolytic graphite electrode. An amorphous carbon top contact electrode is formed on top of the monolayer from a naphthalene precursor using the focused electron beam induced deposition technique. This allows the deposition of a carbon top-contact electrode with well-defined shape, thickness, and precise positioning on the film with nm resolution. These results represent a substantial step toward the realization of integrated molecular electronic devices based on monolayers and carbon electrodes.

First order reversal curves (FORC) analysis of individual magnetic nanostructures using micro-Hall magnetometry

Alongside the development of artificially created magnetic nanostructures, micro-Hall magnetometry has proven to be a versatile tool to obtain high-resolution hysteresis loop data and access dynamical properties. Here we explore the application of First Order Reversal Curves (FORC)-a technique well-established in the field of paleomagnetism for studying grain-size and interaction effects in magnetic rocks-to individual and dipolar-coupled arrays of magnetic nanostructures using micro-Hall sensors. A proof-of-principle experiment performed on a macroscopic piece of a floppy disk as a reference sample well known in the literature demonstrates that the FORC diagrams obtained by magnetic stray field measurements using home-built magnetometers are in good agreement with magnetization data obtained by a commercial vibrating sample magnetometer. We discuss in detail the FORC diagrams and their interpretation of three different representative magnetic systems, prepared by the direct-write Focused Electron Beam Induced Deposition (FEBID) technique: (1) an isolated Co-nanoisland showing a simple square-shaped hysteresis loop, (2) a more complex CoFe-alloy nanoisland exhibiting a wasp-waist-type hysteresis, and (3) a cluster of interacting Co-nanoislands. Our findings reveal that the combination of FORC and micro-Hall magnetometry is a promising tool to investigate complex magnetization reversal processes within individual or small ensembles of nanomagnets grown by FEBID or other fabrication methods. The method provides sub-μm spatial resolution and bridges the gap of FORC analysis, commonly used for studying macroscopic samples and rather large arrays, to studies of small ensembles of interacting nanoparticles with the high moment sensitivity inherent to micro-Hall magnetometry.

Fragmentation pathways of tungsten hexacarbonyl clusters upon electron ionization.

Electron ionization of neat tungsten hexacarbonyl (W(CO)6) clusters has been investigated in a crossed electron-molecular beam experiment coupled with a mass spectrometer system. The molecule is used for nanofabrication processes through electron beam induced deposition and ion beam induced deposition techniques. Positive ion mass spectra of W(CO)6 clusters formed by electron ionization at 70 eV contain the ion series of the type W(CO)n (+) (0 ≤ n ≤ 6) and W2(CO)n (+) (0 ≤ n ≤ 12). In addition, a series of peaks are observed and have been assigned to WC(CO)n (+) (0 ≤ n ≤ 3) and W2C(CO)n (+) (0 ≤ n ≤ 10). A distinct change of relative fragment ion intensity can be observed for clusters compared to the single molecule. The characteristic fragmentation pattern obtained in the mass spectra can be explained by a sequential decay of the ionized organometallic, which is also supported by the study of the clusters when embedded in helium nanodroplets. In addition, appearance energies for the dissociative ionization channels for singly charged ions have been estimated from experimental ion efficiency curves.

Focused Electron and Ion Beam Induced Deposition on Flexible and Transparent Polycarbonate Substrates.

The successful application of focused electron (and ion) beam induced deposition techniques for the growth of nanowires on flexible and transparent polycarbonate films is reported here. After minimization of charging effects in the substrate, sub-100 nm-wide Pt, W, and Co nanowires have been grown and their electrical conduction is similar compared to the use of standard Si-based substrates. Experiments where the substrate is bent in a controlled way indicate that the electrical conduction is stable up to high bending angles, >50°, for low-resistivity Pt nanowires grown by the ion beam. On the other hand, the resistance of Pt nanowires grown by the electron beam changes significantly and reversibly with the bending angle. Aided by the substrate transparency, a diffraction grating in transmission mode has been built based on the growth of an array of Pt nanowires that shows sharp diffraction spots. The set of results supports the large potential of focused beam deposition as a high-resolution nanolithography technique on transparent and flexible substrates. The most promising applications are expected in flexible nano-optics and nanoplasmonics, flexible electronics, and nanosensing.

Enhancement in Electrical Conductance of Pt Decorated Multiwalled Carbon Tubes Using Electron Beam-Induced Deposition Technique

We propose a direct-write approach to decorate the hanging multiwalled carbon tubes (MWCNTs), at the selected sites with platinum (Pt) metal, using electron beam-induced deposition (EBID) technique. As prepared nanostructure is investigated by scanning electron microscopy (SEM), confirming the deposition of Pt nanoclusters on tube surface. The conductance of the individual tube enhances significantly due to Pt deposition at desired locations on the tubes. The value of conductance (in terms of quanta) of the same tube is increased from 3.2 G0 to 11.7 G0 at zero bias after Pt deposition. This enhancement in conductance is explained in terms of change in density of states (DOS) at the Fermi level which results in charge transfer between tubes and nanoclusters. This approach can be used for the applications of tubes in nano-devices which is dependent on the distribution of metal nanostructures, nano gas sensors, and in the interconnections.

Joining of Broken Multiwalled Carbon Nanotubes Using an Electron Beam-Induced Deposition (EBID) Technique

In the present work, joining of broken multiwalled carbon nanotubes (MWCNTs) via an electron beam-induced deposition technique is discussed. Current-induced breakdown caused by Joule heating was achieved by applying an appropriate sweep voltage. Scanning electron microscopy images indicated physical joining of broken tubes. To confirm electrical joining of the tubes, current–voltage measurements of the same tube were carried out before and after joining. The current–voltage characteristics remained ohmic after joining of the broken tube. Furthermore, it was found that deposited platinum (Pt) forms ohmic contacts with different shells of MWCNTs after joining, whereas tungsten (W) does not. This approach provides a significant tool for repairing CNTs in interconnect technologies and assembly of three-dimensional (3D) nanostructures.

Optical field-enhancement in metal nanoparticle arrays contacted by electron beam induced deposition

We study the impact of optical field-enhancement effects on the optoelectronic properties of metal nanoparticle arrays. Applying a focused ion beam lithography in combination with an electron beam induced deposition technique we pattern electrical contacts in a way that they give rise to an electromagnetic field-enhancement. The field-enhancement is directly observed in an enhanced photoconductance of the arrays. Finite-difference time-domain simulations verify that an antenna effect is responsible for the observed increase in the photoconductance.

Graphene based chemical sensor fabrication by means of Focused Ion Beam

Graphene is a material with surprising properties, that very recently aroused the attention of the scientific world for its potential applications in different fields from electronics to sensors. To date, many works have been already published dealt with graphene-based sensor in which the preparation of the devices involves the use of some lithographic method. It is known, however, that typical nano-lithographic processes leave an uncontrolled residue on graphene. In this work we present a graphene based chemiresistor, where the electrode structure is realized by Ion Beam Induced Deposition technique; the current–voltage characteristics of such a device will be investigated in different environments.

Manifold enhancement of electron beam induced deposition rate at grazing incidence

It is shown how a significant drawback of the electron beam induced deposition technique,namely its low deposition rate, can be circumvented. By tilting a sample, a larger part ofthe primary electron beam energy becomes dissipated closer to the interface. This in turnincreases the emission of secondary electrons, largely responsible for the deposition of theadsorbed molecule components on the surface. An order of magnitude increase in thedeposition rate is reported in the fabrication of metal nanowires from organic precursor gas.

Formation of nanoscale platinum and iron oxide structures using electron beam induced deposition techniques

Electron beam induced deposition (EBID) is a promising technique for fabricating nanometre-sized structures in a position-controlled manner. In this technique, organometallic precursors are decomposed by focused electron beams. Then, the non-volatile part of the decomposed precursor deposits on the substrate. As electron beams can be focused to a subnanometre scale in modern electron microscopes, the resolution of EBID is now reaching down to subnanometres. However, the deposits generally contain a large amount of amorphous carbon. This carbon contamination may be the most serious drawback and is preventing practical uses of EBID in nanodevice technology. In this study, nanostructures, such as nanowires, were fabricated by EBID using methyl cyclopenta dienyl platinum trimethyl (MeCpPtMe3) and iron pentacarbonyl (Fe(CO)5) precursors in a scanning electron microscope with a custom-made gas introduction system. After the deposition, nanostructures were heated at 400°C in air for 30 min. to remove contaminated carbon. Then, the nanostructures were observed using a transmission electron microscope (TEM). TEM observation revealed that a post-deposition heat-treatment in air resulted in the removal of carbon. The nanostructures made from MeCpPtMe3 and Fe(CO)5 became pure Pt and a mixture of hematite and maghemite iron oxides, respectively.

Effects of Heat Treatment on Electric Properties of Nanorods Formed by Electron Beam-Induced Deposition

Nanometer-sized rods were fabricated by an electron beam-induced deposition technique with iron pentacarbonyl. The electric properties of the as-deposited and heat-treated nanorods were measured in situ using a transmission electron microscope. The obtained current–voltage curve showed a nonlinear characteristic, and the resistivity was in the order of 10-2 Ω m in the case of the as-deposited nanorods. After a heat treatment at 600 °C in vacuum, the nanorods transformed to α-Fe, and a resistivity of approximately 10-6 Ω m and a metallic characteristic were obtained. This suggests that position- and shape-controlled metallic nanowires can be formed by electron beam-induced deposition combined with heat treatment.

Fabrication of nanofigures by focused electron beam-induced deposition

Contamination lithography has been performed on various metal substrates by focused electron beam-induced deposition (EBID) technique in a field emission scanning electron microscope (FE-SEM). We used pump oil (hydrocarbon) as precursors for EBID. It was found that the growth rate was independent of primary electron energy (500 to 30 keV) but was varied with elements ranging from 0.34 to 2.97 μ/min. Energy dispersive X-ray (EDX) spectroscopy measurement revealed that the grown nanowire contains a substrate element. A complicated mesh patterns with nanofigures was successfully fabricated manually with optimal growth conditions.

電子線誘起蒸着法によるナノ立体構造作製とその組織

電子線誘起蒸着法によるナノ立体構造作製とその組織

On-line nanolithography using electron beam-induced deposition technique

A four-channel gas feeding was installed at a commercial e-beam lithography system. The gas system and the deposition technique were tested with a solid precursor (CpPtMe 3). With this material base we investigated the deposition behaviour on different substrates (Si, SiO x on Si), at different gas pressures and different beam energies ( E 0=2.5 and 15 keV). In all cases a minimum feature size of 30 nm was obtained. The growth of simple point structures both in width and height shows a clear dependence on the pixeltime. The feature size can thus easily be controlled via the pixeltime of the e-beam. In addition to fundamental research, we have produced nanowires and other arrangements by using this technique. All deposition structures were found to be accurately placed in a given wiring by using mix&match-technique.

Beam induced deposition of an ultraviolet transparent silicon oxide film by focused gallium ion beam

We have deposited a silicon oxide (SiOx) film with a high optical transmittance in the DUV region by a focused ion beam induced deposition technique using a gallium ion beam and a mixture of oxygen and TMCTS(1,3,5,7-tetramethylcyclotetrasiloxane) as a source gas. The optical transmittance of a 0.3 μm thick film is higher than 90% at the wavelength of 250 nm. The transmittance of the deposited SiOx film depends on both the source gas and ion beam irradiation conditions. A scaling to explain the transmittance along with the ion beam conditions is proposed.