I. Utke

Focused electron beam induced deposition of gold

Codeposition of hydrocarbons is a severe problem during focused electron beam writing of pure metal nanostructures. When using organometallic precursors, a low metal content carbonaceous matrix embedding and separating numerous nanosized metal clusters is formed. In this work, we present a new and easy approach to obtain high purity gold lines: the use of inorganic PF3AuCl as a precursor. Electrical resistivities as low as 22 µOhms cm at 295 K (ten times the bulk Au value) were obtained. This is to our knowledge the best value for focused electron beam deposition obtained from the vapor phase so far. No special care was taken to prevent hydrocarbon contamination. The deposited nanostructure consists of gold grains varying in size and percolation with beam parameters.

High-resolution magnetic Co supertips grown by a focused electron beam

We present a technique for local growth of high-resolution, high-aspect-ratio magnetic tips and thin adherent magnetic cap coatings on top of batch fabricated scanning force microscopy silicon tips. A focused electron beam of a scanning electron microscope is used for decomposition of a directed cobalt carbonyl vapor flux. Exposure parameters determine the tip geometry and tip length. Deposits consist of cubic Co clusters of 2–5 nm in size dispersed in a stabilizing carbonaceous matrix. Magnetic force microscope sensors having magnetic tip apex diameters between 50 and 240 nm were produced. Tracks of magnetic transitions written in recording media of hard disks were used to characterize tip performance.

Submicrometer Hall devices fabricated by focused electron-beam-induced deposition

Hall devices having an active area of about (500 nm)(2) are fabricated by focused electron-beam-induced deposition. The deposited material consists of cobalt nanoparticles in a carbonaceous matrix. The realized devices have, at room temperature, a current sensitivity of about 1 V/AT, a resistance of a few kilo-ohms, and can be biased with a maximum current of about 1 mA. The room-temperature magnetic field resolution is about 10 muT/Hz(1/2) at frequencies above 1 kHz.

Focused-electron-beam-induced deposition of freestanding three-dimensional nanostructures of pure coalesced copper crystals

We report on direct writing of three-dimensional freestanding nanostructures of Cu by use of a focused electron beam (FEB) and the metalorganic precursor hfac-Cu-TMVS. Freestanding horizontal rods were deposited over about 10 μm length and consist of small 2–5 nm Cu nanocrystals dispersed in an amorphous matrix containing carbon, fluorine, silicon, and oxygen. The freestanding horizontal rods were used as support for further vertical deposits resulting in tips of coalesced facetted Cu nanocrystals of up to 100 nm in size. The almost constant deposition rate of 5–6 nm/s is in contrast to vertical tips on bulk supports, which show a deposition rate decreasing from 23 to 10 nm/s. The above results suggest a thermal decomposition process induced by electron energy absorption.

Electrodes for carbon nanotube devices by focused electron beam induced deposition of gold

Individual carbon nanotubes (CNTs) often occur in randomly dispersed two-dimensional as well as three-dimensional configurations that make device fabrication difficult. Making electrical contact to such CNTs is of practical interest. To this end, we make contact to individual metallic single-walled carbon nanotubes (SWNTs) using the focused electron-beam-induced deposition (FEBID) of pure gold. The SWNTs are grown by chemical vapor deposition on a flat substrate, and the gold leads are made through FEBID using inorganic metallic precursor gas, chloro(trifluorophosphine)gold(I), or AuClPF3, in a high vacuum scanning electron microscope. The same scanning electron microscope is also used to image carbon nanotubes, allowing for simultaneous alignment. We find equivalent one-dimensional resistivities for the SWNTs of 10–15kΩ∕μm for both FEBID gold leads and leads deposited using conventional electron-beam lithography (EBL) and thermal evaporation of gold, suggesting similarly low contact resistances. We use e...

In situ control of the focused-electron-beam-induced deposition process

A simple quantitative method for in situ control of the focused-electron-beam-induced deposition process is discussed and demonstrated with precursors used for Au, Cu, Rh, and SiO2 deposition. A picoamperemeter monitors the electron current flowing through the sample, which reproducibly drops at a characteristic rate to a plateau value during deposition. These parameters are correlated to deposit geometry, composition, and precursor supply. Monte Carlo simulations of electron backscattering and secondary electron emission by the growing structures show excellent agreement with the experiment. The method could apply to a wide range of charged-particle deposition and etching processes.

Annular aperture arrays: study in the visible region of the electromagnetic spectrum

Baida and Van Labeke recently proposed a structure that exhibits a supertransmission of light through an array of nanometric coaxial apertures in a metallic film that has been named an annular aperture array (AAA) [Opt. Commun. 209, 17 (2002); Phys. Rev. B 67, 155314 (2003); J. Microsc. 213, 140 (2003)]. We present the first experimental study, to our knowledge, of an AAA structure in the visible region. For technological reasons, the structure under study does not produce a supertransmission of 80% as in Baida and Van Labeke [Opt. Commun. 209, 17 (2002)]. We built the nanostructure and experimentally recorded its far-field spectral response. This transmission shows only one broad band with a maximum around lambda = 700 nm, giving a maximum efficiency around 17%. A finite-difference time-domain simulation reproduces quite well the obtained transmission spectrum.

Electron beam induced deposition of metallic tips and wires for microelectronics applications

Resistivity measurements and composition analysis of electron beam induced deposition (EBID) with two novel inorganic carbon-free precursors [RhCl(PF3)2]2 (CAS 14876-98-3) and AuCl(PF3) (CAS 141845-34-3) are compared with results obtained from metallorganic CVD precursors Me2?Au-tfa (CAS 63470-53-1) and Me2?Au-hfa (CAS 63470-54-2). A deposit/metal resistivity ratio of 10 was obtained for EBID with AuCl(PF3).

Vertical Cavity Surface Emitting Lasers Incorporating Structured Mirrors Patterned by Electron Beam Lithography

We demonstrate the operation of bottom-emitting vertical cavity surface-emitting lasers (VCSELs) with linear mode polarization which is controlled in an arbitrary orientation by the use of patterned metallic mirrors on top of the VCSEL surface. The top mirror is made in the shape of a 200 nm pitch grating, composed of alternating high reflectivity (Au) and low reflectivity (Cr) metal lines, whose orientation determines the polarization of the laser mode. The gratings were fabricated by high-resolution (<50 nm) electron-beam lithography and lift-off technique, and were aligned with the other parts of the VCSEL structure (top electrode, ion-implanted zone) fabricated by conventional photolithography. Various types of mirror shapes and sizes were fabricated, including square and circular grating envelopes, as well as circular mirrors with an average (radial) Gaussian reflectivity.

High-temperature X-ray measurements of gallates and cuprates

Lattice parameters of gallates REGaO 3 (RE = Nd, Pr, La) and cuprates REBa 2 Cu 3 O 7-δ (RE = Y, Nd) were measured from room temperature up to 1000°C and compared with values cited in the literature.