C. W. Hagen

Delft University Of Technology, Delft, South Holland, Netherlands

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Publications (66)106.09 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The current understanding in the study of focused electron beam induced processing (FEBIP) is that the growth of a deposit is mainly the result of secondary electrons (SEs). This suggests that the growth rate for FEBIP is affected by the SE emission from the support. Our experiments, with membranes thinner than the SE escape depth, confirm this hypothesis. We used membranes of 1.4 and 4.3 nm amorphous carbon as supports. At the very early stage, the growth is support-dominated and the growth rate on a 4.3 nm thick membrane is three times higher than on a 1.4 nm thick membrane. This is consistent with Monte Carlo simulations for SE emission. The results suggest that SEs are dominant in the dissociation of W(CO)6 on thin membranes. The best agreement between simulations and experiment is obtained for SEs with energies between 3 and 6 eV.With this work we revisit earlier experiments, working at a precursor pressure 20 times lower than previously. Then, despite using membranes thinner than the SE escape depth, we did not see an effect on the experimental growth rate. We explain our current results by the fact that very early in the process, the growth becomes dominated by the growing deposit itself.
    Nanotechnology 07/2013; 24(34):345301. · 3.84 Impact Factor
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    ABSTRACT: Using three different precursors [MeCpPtMe3, Pt(PF3)4, and W(CO)6], an ultra-high vacuum surface science approach has been used to identify and rationalize the effects of substrate temperature and electron fluence on the chemical composition and bonding in films created by electron beam induced deposition (EBID). X-ray photoelectron spectroscopy data indicate that the influence of these two processing variables on film properties is determined by the decomposition mechanism of the precursor. For precursors such as MeCpPtMe3 that decompose during EBID without forming a stable intermediate, the film's chemical composition is independent of substrate temperature or electron fluence. In contrast, for Pt(PF3)4 and W(CO)6, the initial electron stimulated deposition event in EBID creates surface bound intermediates Pt(PF3)3 and partially decarbonylated Wx(CO)y species, respectively. These intermediates can react subsequently by either thermal or electron stimulated processes. Consequently, the chemical composition of EBID films created from either Pt(PF3)4 or W(CO)6 is influenced by both the substrate temperature and the electron fluence. Higher substrate temperatures promote the ejection of intact PF3 and CO ligands from Pt(PF3)3 and Wx(CO)y intermediates, respectively, improving the film's metal content. However, reactions of Pt(PF3)3 and Wx(CO)y intermediates with electrons involve ligand decomposition, increasing the irreversibly bound phosphorous content in films created from Pt(PF3)4 and the degree of tungsten oxidation in films created from W(CO)6. Independent of temperature effects on chemical composition, elevated substrate temperatures (>25 °C) in- reased the degree of metallic character within EBID deposits created from MeCpPtMe3 and Pt(PF3)4.
    Journal of Vacuum Science & Technology B Microelectronics and Nanometer Structures 01/2012; 30(5):1805-. · 1.36 Impact Factor
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    ABSTRACT: The effect of 500 eV electrons on nanometer-thick films of the platinum precursor tetrakis(trifluorophosphine)platinum [Pt(PF3)4] has been studied in situ under ultra-high-vacuum (UHV) conditions using a combination of X-ray photoelectron spectroscopy (XPS), mass spectrometry (MS), and high-resolution electron energy loss spectroscopy (HREELS). Electron irradiation of adsorbed Pt(PF3)4 molecules initially proceeds through a single Pt—P bond-cleavage event and the ejection of one PF3 ligand, analogous to the electron-stimulated reactions of Pt(PF3)4 in the gas phase. The electron-stimulated deposition cross section of Pt(PF3)4, σPt(PF3)4, is governed by the rate of this initial Pt—PF3 cleavage event, which is calculated to be 2.5 × 10–15 cm2 at an incident electron energy of 500 eV. In contrast to the initial deposition step, subsequent electron-stimulated reactions of the surface-bound Pt(PF3)3 intermediate occur exclusively through P—F bond cleavage and the release of fluorine into the gas phase. In this second phase of the decomposition process, oxygen uptake into the film is observed because of reactions between water vapor and the coordinatively unsaturated phosphorus atoms formed by P—F bond cleavage. Electron-beam-induced deposition (EBID) of Pt(PF3)4 was also performed by electron irradiating a substrate at room temperature and at higher electron fluxes, in the presence of a constant partial pressure of Pt(PF3)4. The absence of fluorine in these films underscores the role of electron-stimulated P—F bond cleavage, whereas the absence of oxygen highlights the important role that deposition conditions (e.g., substrate temperature and background gas composition) play in determining the ultimate composition of typical EBID films.
    The Journal of Physical Chemistry C. 08/2011; 115(35).
  • V Castaldo, C W Hagen, P Kruit
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    ABSTRACT: Scanning ion microscopy has received a boost in the last decade, thanks to the development of novel ion sources employing light ions, like He(+), or ions from inert gases, like Ne(+) and Ar(+). Scanning ion images, however, might not be as easy to interpret as SEM micrographs. The contrast mechanisms are different, and there is always a certain degree of sample sputtering. The latter effect, on the one hand, prevents assessing the resolution on the basis of a single image, and, on the other hand, limits the probing time and thus the signal-to-noise ratio that can be obtained. In order to fully simulate what happens when energetic ions impact on a sample, a Monte Carlo approach is often used. In this paper, a different approach is proposed. The contrast is simulated using curves of secondary electron yields versus the incidence angle of the beam, while the surface modification prediction is based on similar curves for the sputtering yield. Finally, Poisson noise from primary ions and secondary electrons is added to the image. It is shown that the evaluation of an ion imaging tool cannot be condensed in a single number, like the spot size or the edge steepness, but must be based on a more complex analysis taking into account at least three parameters: sputtering, contrast and signal-to-noise ratio. It is also pointed out that noise contributions from the detector cannot be neglected for they can actually be the limiting factor in imaging with focused ion beams. While providing already good agreement with experimental data in some imaging aspects, the proposed approach is highly modular. Further effects, like edge enhancement and detection, can be added separately.
    Ultramicroscopy 04/2011; 111(8):982-94. · 2.47 Impact Factor
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    ABSTRACT: It is often suggested that the growth in focused electron beam induced processing (FEBIP) is caused not only by primary electrons, but also (and even predominantly) by secondary electrons (SEs). If that is true, the growth rate for FEBIP can be changed by modifying the SE yield. Results from our Monte Carlo simulations show that the SE yield changes strongly with substrate thickness for thicknesses below the SE escape depth. However, our experimental results show that the growth rate is independent of the substrate thickness. Deposits with an average size of about 3 nm were written on 1 and 9 nm thick carbon substrates. The apparent contradiction between simulation and experiment is explained by simulating the SE emission from a carbon substrate with platinum deposits on the surface. It appears that the SE emission is dominated by the deposits rather than the carbon substrate, even for deposits as small as 0.32 nm(3).
    Nanotechnology 03/2011; 22(11):115303. · 3.84 Impact Factor
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    ABSTRACT: Electron beam induced deposition (EBID) is a direct-write lithographic technique that utilizes the dissociation of volatile precursors by a focused electron beam in a low vacuum environment to create nanostructures. Notable advantages of EBID over competing lithographic techniques are that it is a single step process that allows three-dimensional free-standing structures to be created, including features with single-nanometer scale dimensions. However, despite the inherent advantages of EBID, scientific and technological issues are impeding its development as an industrial nanofabrication tool. Perhaps the greatest single limitation of EBID is that metal-containing nanostructures deposited from organometallic precursors typically possess unacceptable levels of organic contamination which adversely affects the material's properties. In addition to the issue of purity, there is also a lack of understanding and quantitative information on the fundamental surface reactions and reaction cross-sections that are responsible for EBID. In this prospective, we describe how surface analytical techniques have begun to provide mechanistic and kinetic insights into the molecular level processes associated with EBID. This has been achieved by observing the effect of electron irradiation on nanometer thick films of organometallic precursors adsorbed onto solid substrates at low temperatures (
    Surface Science 01/2011; 605(3):257-266. · 1.84 Impact Factor
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    ABSTRACT: Lithography techniques based on electron-beam-induced processes are inherently slow compared to light lithography techniques. The authors demonstrate here that the throughput can be enhanced by a factor of 196 by using a scanning electron microscope equipped with a multibeam electron source. Using electron-beam induced deposition with MeCpPtMe3 as a precursor gas, 14 × 14 arrays of Pt-containing dots were deposited on a W/Si3N4/W membrane, with each array of 196 dots deposited in a single exposure. The authors demonstrate that by shifting the array of beams over distances of several times the beam pitch, one can deposit rows of closely spaced dots that, although originating from different beams within the array, are positioned within 5 nm of a straight line.
    Journal of Vacuum Science & Technology B Microelectronics and Nanometer Structures 01/2011; 29. · 1.36 Impact Factor
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    ABSTRACT: This paper demonstrates electron-beam-induced deposition of few-nm-width dense features on bulk samples by using a scanning electron-beam lithography system. To optimize the resultant features, three steps were taken: (1) features were exposed in a repetitive sequence, so as to build up the deposited features gradually across the entire pattern, and thus avoid proximity effects; (2) an additional delay was added between exposures to permit diffusion of reactants into the exposed area; and (3) the exposures were phase-synchronized to the dominant noise source (the 50-Hz line voltage) to minimize the effect of noise. The reasons these steps led to significant improvements in patterning resolution are discussed.
    Journal of Vacuum Science & Technology B Microelectronics and Nanometer Structures 01/2011; 29(6). · 1.36 Impact Factor
  • B. Cook, T. Verduin, C. W. Hagen, P. Kruit
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    ABSTRACT: Emission theory predicts that high brightness cold field emitters can enhance imaging in the electron microscope. This (neglecting chromatic aberration) is because of the large (coherent) probe current available from a high brightness source and is based on theoretically determined values of reduced brightnesses up to 10<sup>14</sup> A /( m <sup>2</sup>  sr   V ) . However, in their analysis, the authors find that statistical Coulomb interactions limit the reduced brightness of even atomically sharp cold field emitters to 10<sup>11</sup> A /( m <sup>2</sup>  sr   V ) and regular tungsten cold field emitters to around 2×10<sup>8</sup> A /( m <sup>2</sup>  sr   V ) . The authors also find that for tip radii in the range from 5 nm to 1 μ m , cold field emitters do not outperform larger Schottky (thermal field) emitters. Although this is applied to only one geometry, they expect that similar results will occur for most other cases due to a distinct difference in the behavior of different beam regimes.
    Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 12/2010; · 1.36 Impact Factor
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    ABSTRACT: The low-voltage foil corrector is a novel type of foil aberration corrector that can correct for both the spherical and chromatic aberration simultaneously. In order to give a realistic example of the capabilities of this corrector, a design for a low-voltage scanning electron microscope with the low-voltage foil corrector is presented. A fully electrostatic column has been designed and characterised by using aberration integrals and ray tracing calculations. The amount of aberration correction can be adjusted relatively easy. The third order spherical and the first order chromatic aberration can be completely cancelled. In the zero current limit, a FW50 probe size of 1.0 nm at 1 kV can be obtained. This probe size is mainly limited by diffraction and by the fifth order spherical aberration.
    Ultramicroscopy 10/2010; 110(11):1411-9. · 2.47 Impact Factor
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    ABSTRACT: Electron beam induced deposition of organometallic precursors has emerged as an effective and versatile method for creating two-dimensional and three-dimensional metal-containing nanostructures. However, to improve the properties and optimize the chemical composition of nanostructures deposited in this way, the electron stimulated decomposition of the organometallic precursors must be better understood. To address this issue, we have employed an ultrahigh vacuum-surface science approach to study the electron induced reactions of dimethyl-(acetylacetonate) gold(III) [ Au <sup> III </sup>( acac ) Me <sub>2</sub>] adsorbed onto solid substrates. Using thin molecular films adsorbed onto cooled substrates, surface reactions, reaction kinetics, and gas phase products were studied in the incident energy regime between 40 and 1500 eV using a combination of x-ray photoelectron spectroscopy (XPS), reflection absorption infrared spectroscopy (RAIRS), and mass spectrometry (MS). XPS and RAIRS data indicate that electron irradiation of Au <sup> III </sup>( acac ) Me <sub>2</sub> is accompanied by the reduction in Au <sup> III </sup> to a metallic Au <sup>0</sup> species embedded in a dehydrogenated carbon matrix, while MS reveals the concomitant evolution of methane, ethane, carbon monoxide, and hydrogen. The electron stimulated decomposition of Au <sup> III </sup>( acac ) Me <sub>2</sub> is first-order with respect to the surface coverage of the organometallic precursor, and exhibits a rate constant that is proportional to the electron flux. At an incident electron energy of 520 eV, the total reaction cross section was ≈3.6×10<sup>-16</sup> cm <- sup>2</sup> . As a function of the incident electron energy, the maximum deposition yield was observed at ≈175 eV. The structure of discrete Au-containing deposits formed at room temperature by rastering an electron beam across a highly ordered pyrolytic graphite substrate in the presence of a constant partial pressure of Au <sup> III </sup>( acac ) Me <sub>2</sub> was also investigated by atomic force microscopy.
    Journal of Applied Physics 04/2010; · 2.21 Impact Factor
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    ABSTRACT: The authors present the first results obtained with their multibeam scanning electron microscope. For the first time, they were able to image 196 (array of 14×14) focused beams of a multielectron beam source on a specimen using single beam scanning electron microscope (SEM) optics. The system consists of an FEI Novanano 200 SEM optics column equipped with a multielectron beam source module. The source module consists of the multibeam source and an accelerator lens. In the multibeam source, the wide angle beam of a high brightness Schottky source is divided into 196 beamlets and focused by an aperture lens array. The accelerator lens is positioned on the image plane of the multibeam source to direct the beams toward the SEM column. The array of source images is further imaged by the SEM magnetic lenses, and the beam opening angle is defined at the variable aperture of the SEM. The system is designed to deliver 14×14 arrays of beamlets with a minimum probe size of 1 nm. In this article, the performance of the system is examined for a fixed magnification case.
    Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 01/2010; 28(6):C6G5-C6G10. · 1.36 Impact Factor
  • Journal of Vacuum Science & Technology B Microelectronics and Nanometer Structures 01/2010; 28. · 1.36 Impact Factor
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    ABSTRACT: The total cross section has been measured for the electron induced dissociation of trimethyl (methylcyclopentadienyl) platinum (IV) [MeCpPt(IV)Me3], a Pt precursor often used in focused electron beam induced processing (FEBIP), for incident electron energies ranging between 3–3 keV. Measurements were performed for the precursor in the adsorbed state under ultrahigh vacuum conditions. The techniques used in this study were temperature programmed desorption, x-ray photoelectron spectroscopy and mass spectrometry. Two surfaces were used in these experiments, amorphous carbon overlayers containing embedded Pt atoms (a:C-Pt), formed by the electron decomposition of the Pt precursor, and atomically clean Au. The results from these three experiments revealed a comparatively low total cross section at 8 eV (4.2±0.3×10−17 cm2 on the a:C-Pt and 1.4±0.1×10−17 cm2 on the Au) that increases with increasing incident electron energy, reaching a maximum at around 150 eV (4.1±0.5×10−16 cm2 on the a:C-Pt and 2.3±0.2×10−16 cm2 on the clean Au), before decreasing at higher incident electron energies, up to 3000 eV. Differences in the measured cross sections between Au and a:C-Pt surfaces demonstrate that the substrate can influence the reaction cross section of adsorbed species. Temperature programmed desorption was also used to measure the adsorption energy of MeCpPt(IV)Me3, which was found to depend on both the substrate and the adsorbate coverage. The work in this paper demonstrates that surface science techniques can be used to quantitatively determine the total cross section of adsorbed FEBIP precursors for electron induced dissociation as a function of incident electron energy. These total cross section values are necessary to obtain quantitatively accurate information from FEBIP models and to compare the reaction efficiencies of different precursors on a quantitative basis.
    Journal of Applied Physics 10/2009; 106(7):074903-074903-9. · 2.21 Impact Factor
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    A Botman, J J L Mulders, C W Hagen
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    ABSTRACT: The creation of functional nanostructures by electron-beam-induced deposition (EBID) is becoming more widespread. The benefits of the technology include fast 'point-and-shoot' creation of three-dimensional nanostructures at predefined locations directly within a scanning electron microscope. One significant drawback to date has been the low purity level of the deposition. This has two independent causes: (1) partial or incomplete decomposition of the precursor molecule and (2) contamination from the residual chamber gas. This frequently limits the functionality of the structure, hence it is desirable to improve the decomposition and prevent the inclusion of contaminants. In this contribution we review and compare for the first time all the techniques specifically aimed at purifying the as-deposited impure EBID structures. Despite incomplete and scattered data, we observe some general trends: application of heat (during or after deposition) is usually beneficial to some extent; working in a favorable residual gas (ultra-high vacuum set-ups or plasma cleaning the chamber) is highly recommended; gas mixing approaches are extremely variable and not always reproducible between research groups; and carbon-free precursors are promising but tend to result in oxygen being the contaminant species rather than carbon. Finally we highlight a few novel approaches.
    Nanotechnology 10/2009; 20(37):372001. · 3.84 Impact Factor
  • A E Grigorescu, C W Hagen
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    ABSTRACT: In the past decade, the feature size in ultra large-scale integration (ULSI) has been continuously decreasing, leading to nanostructure fabrication. Nowadays, various lithographic techniques ranging from conventional methods (e.g. photolithography, x-rays) to unconventional ones (e.g. nanoimprint lithography, self-assembled monolayers) are used to create small features. Among all these, resist-based electron beam lithography (EBL) seems to be the most suitable technique when nanostructures are desired. The achievement of sub-20-nm structures using EBL is a very sensitive process determined by various factors, starting with the choice of resist material and ending with the development process. After a short introduction to nanolithography, a framework for the nanofabrication process is presented. To obtain finer patterns, improvements of the material properties of the resist are very important. The present review gives an overview of the best resolution obtained with several types of both organic and inorganic resists. For each resist, the advantages and disadvantages are presented. Although very small features (2-5 nm) have been obtained with PMMA and inorganic metal halides, for the former resist the low etch resistance and instability of the pattern, and for the latter the delicate handling of the samples and the difficulties encountered in the spinning session, prevent the wider use of these e-beam resists in nanostructure fabrication. A relatively new e-beam resist, hydrogen silsesquioxane (HSQ), is very suitable when aiming for sub-20-nm resolution. The changes that this resist undergoes before, during and after electron beam exposure are discussed and the influence of various parameters (e.g. pre-baking, exposure dose, writing strategy, development process) on the resolution is presented. In general, high resolution can be obtained using ultrathin resist layers and when the exposure is performed at high acceleration voltages. Usually, one of the properties of the resist material is improved to the detriment of another. It has been demonstrated that aging, baking at low temperature, immediate exposure after spin coating, the use of a weak developer and development at a low temperature increase the sensitivity but decrease the contrast. The surface roughness is more pronounced at low exposure doses (high sensitivity) and high baking temperatures. A delay between exposure and development seems to increase both contrast and the sensitivity of samples which are stored in a vacuum after exposure, compared to those stored in air. Due to its relative novelty, the capabilities of HSQ have not been completely explored, hence there is still room for improvement. Applications of this electron beam resist in lithographic techniques other than EBL are also discussed. Finally, conclusions and an outlook are presented.
    Nanotechnology 08/2009; 20(29):292001. · 3.84 Impact Factor
  • Leon van Kouwen, Aurelien Botman, Cornelis W Hagen
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    ABSTRACT: Electron-beam-induced deposition allows the creation of three-dimensional nanodevices within a scanning electron microscope. Typically the dimensions of the fabricated structure are from 20 nm to several micrometers. Until now the record for the smallest deposited feature in an SEM was 3.5 nm, measured by an indirect method. We have achieved a nanodot having a full width half-maximum of 2.8 +/- 0.3 nm, measured directly in the same microscope after deposition.
    Nano Letters 05/2009; 9(5):2149-52. · 13.03 Impact Factor
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    ABSTRACT: The effect of 500 eV electrons on nanometer scale thick films of trimethyl(methylcyclopentadienyl)platinum(IV) (MeCpPtIVMe3), were studied in situ, under ultrahigh vacuum conditions using a combination of temperature-programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), mass spectrometry, and reflection absorption infrared spectroscopy. TPD results revealed the presence of a monolayer state, with a desorption energy >10 kJ mol−1 larger than the multilayer. XPS data indicate that electron beam induced decomposition of adsorbed MeCpPtIVMe3 produced a carbonaceous film that contained Pt atoms in an electronic state intermediate between metallic Pt and Pt(IV). In addition to Pt(IV) reduction, electron beam irradiation was also accompanied by the evolution of methane and hydrogen from the adsorbate layer and the loss of C−H groups. The rate of Pt(IV) reduction and methane production and the loss of C−H groups from the film were all proportional to the MeCpPtIVMe3 coverage and the incident electron flux. Rate constants for all three processes were comparable, yielding an average reaction cross section of 2.2 × 10−16 cm2 for 500 eV electrons. Changes in the chemical composition of the adsorbate layer as a result of electron beam irradiation were consistent with a process in which one carbon atom desorbs for each MeCpPtIVMe3 molecule that decomposes. A comparison of the gas-phase products observed during the electron irradiation of adsorbed MeCpPtIVMe3 and CpPtIVMe3 support the idea that electron-stimulated decomposition of these platinum precursors involves by Pt−CH3 bond cleavage.
    Journal of Physical Chemistry C - J PHYS CHEM C. 01/2009; 113(6).
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    ABSTRACT: Directed assembly of nano-particles by charged patterns on an insulator surface is a method that has been applied before, but the creation of the charged patterns was a time consuming process in previous work. Here a scanning electron microscope (SEM) is used to speed up the charging process. The main challenges do not lie in focusing the electron beam but in storing the charge in the insulator in a highly localized way. The present paper shows the first promising results of directing nano-particles to predefined charge patterns on insulators, where the charge is created with a finely focused electron beam. The nano-particles (palladium) are created in an Ar atmosphere with a glowing wire generator (GWG). A narrow size interval of charged particles is selected by a mobility analyzer. From gas suspension they are deposited onto the charge patterns.
    Microelectronic Engineering 01/2009; 86:803-805. · 1.22 Impact Factor
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    ABSTRACT: In this paper we present a method based on electron beam induced deposition (EBID) to fabricate small electrodes with sub-10nm gaps as required e.g. in single electron devices. EBID provides nanometer resolution combined with a relatively high throughput and reproducibility. Some known drawbacks of EBID are the limited choice of materials, inclusion of large amounts of carbon and low aspect ratio (AR) in the sub-10nm regime. These drawbacks have been circumvented by using EBID deposits as an etch mask to pattern other materials, rather than using EBID to deposit the electrodes directly. Using this method 15–20nm wide electrodes separated by a 7nm gap were successfully fabricated.
    Microelectronic Engineering - MICROELECTRON ENG. 01/2009; 86(4):961-964.

Publication Stats

509 Citations
106.09 Total Impact Points


  • 1996–2013
    • Delft University Of Technology
      • • Faculty of Applied Sciences (AS)
      • • Applied Geophysics and Petrophysics
      Delft, South Holland, Netherlands
  • 2011
    • Technical University of Denmark
      • Center for Electron Nanoscopy
      København, Capital Region, Denmark
  • 2010
    • Johns Hopkins University
      • Department of Chemistry
      Baltimore, MD, United States