Electron Beam Induced Deposition Technique Research Articles

3D assembly of carbon nanotubes for fabrication of field-effect transistors through nanomanipulation and electron-beam-induced deposition

Three-dimensional carbon nanotube field-effect transistors (3D CNTFETs) possess predictable characteristics that rival those of planar CNTFETs and Si-based MOSFETs. However, due to the lack of a reliable assembly technology, they are rarely reported on, despite the amount of attention they receive. To address this problem, we propose the novel concept of a 3D CNTFET and develop its assembly strategy based on nanomanipulation and the electron-beam-induced deposition (EBID) technique inside a scanning electron microscope (SEM). In particular, the electrodes in our transistor design are three metallic cuboids of the same size, and their front, top and back surfaces are all wrapped up in CNTs. The assembly strategy is employed to build the structure through a repeated basic process of pick-up, placement, fixing and cutting of CNTs. The pick-up and placement is performed through one nanomanipulator with four degrees of freedom. Fixing is carried out through the EBID technique so as to improve the mechanical and electrical characteristics of the CNT/electrodes connection. CNT cutting is undertaken using the typical method of electrical breakdown. Experimental results showed that two CNTs were successfully assembled on the front sides of the cubic electrodes. This validates our assembly method for the 3D CNTFET. Also, when contact resistance was measured, tens of kilohms of resistance was observed at the CNT-EBID deposition-FET electrodes junction.. This manifests the electrical reliability of our assembly strategy.

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.

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.

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.

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.

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.

Enhanced imaging of biomolecules with electron beam deposited tips for scanning force microscopy

Tip/sample interaction on the scanning force microscope (SFM) is a particularly difficult problem with biological materials. One major factor affecting image quality is the tip shape. Improved electron beam induced deposition technique with a scanning electron microscope (SEM) was used for the reproducible fabrication of carbon sharp tips on the end of commercially available silicon nitride cantilevers for scanning force microscopy. By aligning a fine focused beam of 20 nm diameter directly down the axis of the pyramidal tip at electron energy of 20 kV, carbon deposits grow with full cone angle of about 25°, cone length of 2 μm, and radii of curvature down to 10 nm, making these e-beam tips suitable for biomolecules imaging. The tip dimensions also were controlled by adjusting the beam parameters. Three different types of SFM tips were used to image tobacco mosaic virus (TMV). Conventional pyramidal tips appeared generally worse for imaging helical particles of TMV than SEM-deposited tips which were found more robust than commercially available conical tips. The use of sharper tips for SFM imaging of protein DNA revealed a 25% improvement in lateral resolution.