Johannes Jacobus Lambertus Mulders

Electron postgrowth irradiation of platinum-containing nanostructures grown by electron-beam-induced deposition from Pt(PF3)4

The material grown in a scanning electron microscope by electron beam-induced deposition (EBID) using Pt(PF3)4 precursor is shown to be electron beam sensitive. The effects of deposition time and postgrowth electron irradiation on the microstructure and resistivity of the deposits were assessed by transmission electron microscopy, selected area diffraction, and four-point probe resistivity measurements. The microstructure, notably the platinum nanocrystallite grain size, is shown to evolve with electron fluence in a controllable manner. The resistivity was observed to decrease as a result of postgrowth electron irradiation, with the lowest observed value of 215±15????cm. The authors demonstrate that electron beam-induced changes in microstructure can be caused using electron fluences similar to those used during the course of EBID and suggest that the observed effects can be used to tailor the microstructure and functionality of deposits grown by EBID in situ without breaking vacuum.

Resist-free fabricated carbon nanotube field-effect transistors with high-quality atomic-layer-deposited platinum contacts

Carbon nanotubes are considered as alternative channel material for future transistors, but several challenges exist for reliable fabrication of these devices. In this work, carbon nanotube field-effect transistors (CNTFETs) were fabricated by patterning of Pt contacts using a combination of electron beam induced deposition and area-selective atomic layer deposition (ALD). This bottom-up technique eliminates compatibility issues caused by the use of resist films and lift-off steps. Electrical characterization of a set of 33 CNTFETs reveals that using this direct-write ALD process for Pt patterning yields improved contacts as compared to evaporated Pt, most likely due to improved wettability of the contacts on the carbon nanotube. Moreover, these CNTFETs can be characterized as unipolar p-type transistors with a very low off-state current.

Electron Beam-Induced Deposition for Atom Probe Tomography Specimen Capping Layers.

Six precursors were evaluated for use as in situ electron beam-induced deposition capping layers in the preparation of atom probe tomography specimens with a focus on near-surface features where some of the deposition is retained at the specimen apex. Specimens were prepared by deposition of each precursor onto silicon posts and shaped into sub-70-nm radii needles using a focused ion beam. The utility of the depositions was assessed using several criteria including composition and uniformity, evaporation behavior and evaporation fields, and depth of Ga+ ion penetration. Atom probe analyses through depositions of methyl cyclopentadienyl platinum trimethyl, palladium hexafluoroacetylacetonate, and dimethyl-gold-acetylacetonate [Me2Au(acac)] were all found to result in tip fracture at voltages exceeding 3 kV. Examination of the deposition using Me2Au(acac) plus flowing O2 was inconclusive due to evaporation of surface silicon from below the deposition under all analysis conditions. Dicobalt octacarbonyl [Co2(CO)8] and diiron nonacarbonyl [Fe2(CO)9] depositions were found to be effective as in situ capping materials for the silicon specimens. Their very different evaporation fields [36 V/nm for Co2(CO)8 and 21 V/nm for Fe2(CO)9] provide options for achieving reasonably close matching of the evaporation field between the capping material and many materials of interest.

Applications of an in-situ Low Energy Argon Ion Source for Improvement of TEM and SEM Sample Quality

An in-situ low energy ion source for SEM and DualBeam [1] is a new tool that could have a great number of applications that include, for example, reduction of the layer damaged by Ga ions in the TEM lamellae fabricated with Focused Ion beam, fine polishing of the sample surface in order to obtain EBSD patterns of the highest quality, or removal of residual hydrocarbons from the sample surface prior to high resolution SEM imaging.

A Static Low Energy Ion Source for Local Surface Modification

A new in-situ low energy ion source for SEM and DualBeam has been designed. The static beam of low energy gaseous ions such as Ar, O or Xe can be used for a local modification of the sample surface. Typical energies are in the range 5 500 V, covering the interaction types from chemical reaction to reactive ion etching and to ion milling, for energies above the milling threshold. The source is based on the following principle: electrons from the SEM’s electron beam partially convert an atomic or molecular gas flow into a beam of ions directed towards a biased sample. A schematic set up is shown in figure 1. A small nozzle delivers the gas and the electron beam enters this nozzle through a slotted hole. The beam is scanned in this slotted hole, penetrates the gas flow and generates thermal ions both by direct ionization and by ionization from beam interactions with the wall of the nozzle. The ions are pulled out of the nozzle by the protruding fields from the biased sample which is located at a short distance from the nozzle: the ions are accelerated in this electrostatic field and directed towards the sample. The slotted entry hole is roughly located at half the inner nozzle diameter from the edge.

A New In-situ Broad Ion Beam, With Energy Range 1 – 500 eV

The interest in low energy ion beams (typically Ar at 50 – 500 eV), is increasing and finds applications in surface clean up, such as removal of hydrocarbons and oxide layers and in fields related to reactive ion etching. Also the removal of Ga + ions and the amorphous layer in a TEM lamella prepared with FIB is interesting. Within the environment of an SEM or DualBeam a new ion source has been constructed. The ion source is based on a narrow gas channel, in which the atoms are converted into ions using direct ionization by the primary electron beam of the system. This local ionization is primarily driven by the electron ionization cross-section of the gas involved, as a function of the primary electron beam energy. Opposite the channel is a surface at potential -V and at gap distance d (Figure 1). The resulting field (V/d) between this surface and the channel-output, will induce ion acceleration towards the surface: in this way a stationary broad beam of ions with well-defined energy is created. In this set-up the ion energy and the ion current are decoupled parameters and hence can be chosen each within their practical boundaries. In case the gas type is changed, the ionization only scales with the respective cross-section of the applied gas. The behavior of ion source has been simulated with both Opera simulation software and GEANT4 [1], using the actual geometrical set up and physical data as input. This allows to study the influence of the most relevant parameters, including the geometry and to compare it to measured values -using a method described belowwith the aim to optimize the source for its application.