ORCID Profile
0000-0003-2235-7441
Current Organisation
University of Jyväskylä
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Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3RA90142D
Publisher: Elsevier BV
Date: 07-2007
Publisher: Elsevier BV
Date: 03-2003
Publisher: American Vacuum Society
Date: 05-2009
DOI: 10.1116/1.3117281
Abstract: The capability of collimators to define beams of MeV ions with sub-100nm dimensions has recently been demonstrated. Such nanometer beams have potential applications in MeV ion-beam lithography, which is the only maskless technique capable of producing extremely high aspect-ratio micro- and nanostructrures, as well as in high resolution MeV ion-beam imaging. Ion scattering from the collimator edges can be a resolution-restricting factor in these applications. Scattering processes at edges are difficult to study using conventional simulation codes because of the complicated geometry. In this part of our work, the authors used the GEANT4 toolkit as a simulation tool for studying the behavior of beams of 3MeV He ions with 0.2–1mrad ergence impinging onto the programmable proximity aperture comprising four 100-μm-thick Ta plates. The transmission and scattering from the aperture are asymmetric due to the aperture design. For a perfectly parallel beam, the fluence of ions scattered from the aperture edges is spread over large areas. The enhancement of the fluence from the edge-scattered ions is two to three orders of magnitude smaller compared to the incident-beam fluence. Therefore, the edge scattering is not a resolution-restricting factor, and the sub-100nm resolution is achievable. However, for erging beams, the significant penumbra broadening of the beam spots restricts the attainable resolution. In lithography applications, the halo associated with penumbra broadening causes pattern edge roughening by producing single ion tracks in close vicinity to the pattern element edges.
Publisher: Elsevier BV
Date: 08-2006
Publisher: Elsevier BV
Date: 07-2007
Publisher: Oxford University Press (OUP)
Date: 08-2008
DOI: 10.1093/RPD/NCN162
Abstract: In retrospective radon measurements, the 22-y half life of (210)Pb is used as an advantage. (210)Pb is often considered to be relatively immobile in glass after alpha recoil implanted by (222)Rn progenies. The diffusion of (210)Pb could, however, lead to uncertain wrong retrospective radon exposure estimations if (210)Pb is mobile and can escape from glass, or lost as a result of cleaning-induced surface modification. This diffusion was studied by a radiotracer technique, where (209)Pb was used as a tracer in a glass matrix for which the elemental composition is known. Using the ion guide isotope separator on-line technique, the (209)Pb atoms were implanted into the glass with an energy of 39 keV. The diffusion profiles and the diffusion coefficients were determined after annealing at 470-620 degrees C and serial sectioning by ion sputtering. In addition, the effect of surface cleaning on diffusion was tested. From the Arrhenius fit, the activation enthalpy (H) was determined, which is equal to 3.2 +/- 0.2 eV, and also the pre-exponential factor D(0), in the order of 20 m(2)s(-1). This result confirms the assumption that over a time period of 50 y (209)Pb (and (210)Pb) is effectively immobile in the glass. The boundary condition obtained from the measurements had the characteristic of a sink, implying loss of (209)Pb in the topmost surface at high temperatures.
Publisher: Elsevier BV
Date: 05-2008
Publisher: Elsevier BV
Date: 08-2020
Publisher: Elsevier BV
Date: 05-2008
Publisher: AIP Publishing
Date: 03-2006
DOI: 10.1063/1.2178393
Abstract: The short-ranged bonding structure of organosilicate glasses can vary to a great extent and is directly linked to the mechanical properties of the thin film material. The combined action of ultraviolet (UV) radiation and thermal activation is shown to generate a pronounced rearrangement in the bonding structure of thin organosilicate glass films involving no significant compositional change or film densification. Nuclear magnetic resonance spectroscopy indicates loss of –OH groups and an increase of the degree of cross-linking of the organosilicate matrix for UV-treated films. Fourier transform infrared spectroscopy shows a pronounced enhancement of the Si–O–Si network bond structure, indicating the formation of more energetically stable silica bonds. Investigation with x-ray reflectivity and ellipsometric porosimetry indicated only minor film densification. As a consequence, the mechanical properties of microporous organosilicate dielectric films are substantially enhanced while preserving the organosilicate nature and pristine porosity of the films. UV-treated films show an increase in elastic modulus and hardness of more than 40%, and a similar improvement in fracture energy compared to untreated films. A minor increase in material dielectric constant from 3.0 to 3.15 was observed after UV treatment. This mechanism is of high relevance for the application of organosilicate glasses as dielectric materials for microelectronics interconnects, for which a high mechanical stability and a low dielectric constant are both essential film requirements.
Publisher: American Vacuum Society
Date: 09-2200
DOI: 10.1116/1.2978173
Abstract: A novel MeV ion beam programmable proximity aperture lithography system has been constructed at the Accelerator Laboratory of the University of Jyväskylä, Finland. This facility can be used to fabricate three dimensional microstructures in thick (& μm) polymer resist such as polymethylmethacrylate. In this method, MeV ion beams from the 1.7 MV pelletron and K130 cyclotron accelerators are collimated to a beam spot of rectangular shape. This shape is defined by a computer-controlled aperture made of a pair of L-shaped Ta blades which are in close proximity to the s le to minimize the penumbra broadening. Here the authors report on development of the system, the controlling software, the calibration procedures, investigations of multiple scattering effects, and present illustrative results using 3MeV He2+4 ion beams for lithography and 56MeV N3+14 ion beams for creating patterns of regions with ion tracks.
Publisher: Elsevier BV
Date: 06-2009
Publisher: Elsevier BV
Date: 07-2014
Publisher: American Vacuum Society
Date: 05-2009
DOI: 10.1116/1.3117257
Abstract: Collimators are widely used to define MeV ion beams. Recent studies have shown the capability of collimators to define beams of MeV ions with sub-100nm dimensions. Such nanometer beams have potential applications in MeV ion-beam lithography, which is the only maskless technique capable of producing extremely high aspect-ratio micro- and nanostructrures, as well as in high-resolution MeV ion-beam-based tomography. The ion scattering from the collimator edges that define the beam can be a resolution-restricting factor in these applications. Scattering processes at edges are difficult to study using conventional simulation codes because of the complicated geometry. In this part of the work, the authors used the GEANT4 toolkit as a simulation tool for studying the behavior of ions impinging onto, or in close proximity to, a single straight aperture edge. Results from simulations are presented for realistic beams of 3MeV He ions with 0.2–1mrad ergence incident on a 100-μm-thick Ta plate. The contribution from grazing scattering of ions impinging under glancing angles of incidence & ° on the slit-edge surface plane can degrade the beam spot size and shape. Ray-tracing simulations were also performed to investigate the trajectories of ions impinging on the aperture edge and in close proximity to it.
No related grants have been discovered for Timo Sajavaara.