| 1. |
- Ahvenniemi, Esko, et al.
(författare)
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Recommended reading list of early publications on atomic layer deposition-Outcome of the "Virtual Project on the History of ALD"
- 2017
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Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 35:1
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Forskningsöversikt (refereegranskat)abstract
- Atomic layer deposition (ALD), a gas-phase thin film deposition technique based on repeated, self-terminating gas-solid reactions, has become the method of choice in semiconductor manufacturing and many other technological areas for depositing thin conformal inorganic material layers for various applications. ALD has been discovered and developed independently, at least twice, under different names: atomic layer epitaxy (ALE) and molecular layering. ALE, dating back to 1974 in Finland, has been commonly known as the origin of ALD, while work done since the 1960s in the Soviet Union under the name "molecular layering" (and sometimes other names) has remained much less known. The virtual project on the history of ALD (VPHA) is a volunteer-based effort with open participation, set up to make the early days of ALD more transparent. In VPHA, started in July 2013, the target is to list, read and comment on all early ALD academic and patent literature up to 1986. VPHA has resulted in two essays and several presentations at international conferences. This paper, based on a poster presentation at the 16th International Conference on Atomic Layer Deposition in Dublin, Ireland, 2016, presents a recommended reading list of early ALD publications, created collectively by the VPHA participants through voting. The list contains 22 publications from Finland, Japan, Soviet Union, United Kingdom, and United States. Up to now, a balanced overview regarding the early history of ALD has been missing; the current list is an attempt to remedy this deficiency.
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| 2. |
- Etula, Jarkko, et al.
(författare)
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Room-Temperature Micropillar Growth of Lithium-Titanate-Carbon Composite Structures by Self-Biased Direct Current Magnetron Sputtering for Lithium Ion Microbatteries
- 2019
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Ingår i: Advanced Functional Materials. - : WILEY-V C H VERLAG GMBH. - 1616-301X .- 1616-3028. ; 29:42
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Tidskriftsartikel (refereegranskat)abstract
- Here, an unidentified type of micropillar growth is described at room temperature during conventional direct-current magnetron sputtering (DC-MS) deposition from a Li4Ti5O12+graphite sputter target under negative substrate bias and high operating pressure. These fabricated carbon-Li2O-TiO2 microstructures consisting of various Li4Ti5O12/Li2TiO3/LixTiO2 crystalline phases are demonstrated as an anode material in Li-ion microbatteries. The described micropillar fabrication method is a low-cost, substrate independent, single-step, room-temperature vacuum process utilizing a mature industrial complementary metal-oxide-semiconductor (CMOS)-compatible technology. Furthermore, tentative consideration is given to the effects of selected deposition parameters and the growth process, as based on extensive physical and chemical characterization. Additional studies are, however, required to understand the exact processes and interactions that form the micropillars. If this facile method is further extended to other similar metal oxide-carbon systems, it could offer alternative low-cost fabrication routes for microporous high-surface area materials in electrochemistry and microelectronics.
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| 3. |
- Gorelick, Sergey, et al.
(författare)
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Growth of osteoblasts on lithographically modified surfaces
- 2007
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier. - 0168-583X .- 1872-9584. ; 260:1, s. 130-135
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Tidskriftsartikel (refereegranskat)abstract
- Here we report about preliminary investigations on developing substrates for culturing osteoblasts, the cells responsible for production of mineralised bone, by lithographically modifying the surfaces of several materials. The proton beam writing system at the National University of Singapore was used to fabricate high aspect ratio structures in PMMA, while two-dimensional low aspect ratio structures were fabricated using conventional electron beam lithography (EBL) and UV lithography (UVL) in SU-8. It was found that oxygen plasma treatment of structured SU-8 surfaces changed the surface layer and significantly improved cell attachment and proliferation. Cells grown on patterned thick PMMA exhibit a remarkable geometry-dependent behaviour.
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| 4. |
- Jogi, Indrek, et al.
(författare)
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Investigation of ZrO2-Gd2O3 Based High-k Materials as Capacitor Dielectrics
- 2010
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 157:10, s. G202-G210
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Tidskriftsartikel (refereegranskat)abstract
- Atomic layer deposition (ALD) of ZrO2-Gd2O3 nanolaminates and mixtures was investigated for the preparation of a high permittivity dielectric material. Variation in the relative number of ALD cycles for constituent oxides allowed one to obtain films with controlled composition. Pure ZrO2 films possessed monoclinic and higher permittivity cubic or tetragonal phases, whereas the inclusion of Gd2O3 resulted in the disappearance of the monoclinic phase. Changes in phase composition were accompanied with increased permittivity of mixtures and laminates with low Gd content. Further increase in the lower permittivity Gd2O3 content above 3.4 cat. % resulted in the decreased permittivity of the mixtures. Leakage currents generally decreased with increasing Gd content, whereby laminated structures demonstrated smaller leakage currents than mixed films at a comparable Gd content. Concerning the bottom electrode materials, the best results in terms of permittivity and leakage currents were achieved with Ru, allowing a capacitance equivalent oxide thickness of similar to 1 nm and a current density of 3 X 10(-8) A/cm(2) at 1 V. Charge storage values up to 60 nC/mm(2) were obtained for mixtures and laminates with thickness below 30 nm. In general, at electric fields below 2-3 MV/cm, normal and trap-compensated Poole-Frenkel conduction mechanisms were competing, whereas at higher fields, Fowler-Nordheim and/or trap-assisted tunneling started to dominate.
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| 5. |
- Kukli, Kaupo, et al.
(författare)
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Atomic layer deposition of Ru films from bis(2,5-dimethylpyrrolyl)ruthenium and oxygen
- 2012
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 520:7, s. 2756-2763
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Tidskriftsartikel (refereegranskat)abstract
- Ru thin films were grown on hydrogen terminated Si, SiO2, Al2O3, HfO2, and TiO2 surfaces by atomic layer deposition from bis(2,5-dimethylpyrrolyl)ruthenium precursor and oxygen. The 4-20 nm thick films on these surfaces consisted of nanocrystalline hexagonal metallic ruthenium, regardless of the deposition temperature. At the lowest temperatures examined, 250-255 degrees C, the growth of the Ru films was favored on silicon, compared to the growth on Al2O3, TiO2 and HfO2. At higher temperatures the nucleation and growth of Ru became enhanced in particular on HfO2, compared to the process on silicon. At 320-325 degrees C, no growth occurred on Si-H and SiO2-covered silicon. Resistivity values down to 18 mu Omega.cm were obtained for ca. 10 nm thick Ru films.
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| 6. |
- Kukli, Kaupo, et al.
(författare)
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Effect of selected atomic layer deposition parameters on the structure and dielectric properties of hafnium oxide films
- 2004
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Ingår i: Journal of Applied Physics. ; 96:9, s. 5298-5307
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Tidskriftsartikel (refereegranskat)abstract
- Hf02 films were atomic layer deposited from HfCl4 and H20 onSi(lOO) in the temperature range of 226-750 °C. The films consisted of dominantly the monoclinic polymorph. Elastic recoildetection analysis revealed high residual chlorine and hydrogen contents (2-5 at. %) in the films grown below 300-350 °C. The content of residual hydrogen and chlorine monotonouslydecreased with increasing growth temperature. The effctive permittivity insignificantly depended on thegrowth temperature and water partial pressure. Capacitance-voltage curves exhibited market hysteresis especially in the films grown at 400-450 ° C, and demonstrated enhanced distortions likely due to the increased trap densities in the films grown at 700-750 °C. Changes in water pressure led to some changes in the extent of crystallization, but did not induce any clear change; in the capacitance of the dielectric layer.
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| 7. |
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| 8. |
- Laitinen, Mikko, et al.
(författare)
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Mobility determination of lead isotopes in glass for retrospective radon measurements
- 2008
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 131:3, s. 212-216
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Tidskriftsartikel (refereegranskat)abstract
- In retrospective radon measurements, the 22-y half life of Pb-210 is used as an advantage. Pb-210 is often considered to be relatively immobile in glass after alpha recoil implanted by Rn-222 progenies. The diffusion of Pb-210 could, however, lead to uncertain wrong retrospective radon exposure estimations if Pb-210 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 Pb-209 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 Pb-209 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 Pb-209 (and Pb-210) is effectively immobile in the glass. The boundary condition obtained from the measurements had the characteristic of a sink, implying loss of Pb-209 in the topmost surface at high temperatures.
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| 9. |
- Vockenhuber, Christof, et al.
(författare)
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Energy-loss straggling of 2–10 MeV/u Kr ions in gases
- 2013
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Ingår i: European Physical Journal D. - : EDP Sciences: EPJ. - 1434-6060 .- 1434-6079. ; 67:7
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Tidskriftsartikel (refereegranskat)abstract
- Measurements have been performed on a time-of-flight setup at the Jyväskylä K130 cyclotron, aiming at energy-loss straggling of heavy ions in gases. Theoretical predictions based on recently developed theory as well as an empirical interpolation formula predict that straggling can be more than ten times higher than Bohr straggling in the MeV/u regime. Our measurements with up to 9.3 MeV/u Kr ions on He, N2, Ne and Kr targets confirm this feature. Our calculations show the relative contributions of linear straggling, bunching including packing, and charge exchange. Our results for stopping cross sections are compatible with values from the literature.
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| 10. |
- Wen, Chenyu, 1990-, et al.
(författare)
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Generalized Noise Study of Solid-State Nanopores at Low Frequencies
- 2017
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Ingår i: ACS Sensors. - : American Chemical Society (ACS). - 2379-3694. ; 2:2, s. 300-307
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Tidskriftsartikel (refereegranskat)abstract
- Nanopore technology has been extensively investigated for analysis of biomolecules, and a success story in this field concerns DNA sequencing using a nanopore chip featuring an array of hundreds of biological nanopores (BioNs). Solid-state nanopores (SSNs) have been explored to attain longer lifetime and higher integration density than what BioNs can offer, but SSNs are generally considered to generate higher noise whose origin remains to be confirmed. Here, we systematically study lowfrequency (including thermal and flicker) noise characteristics of SSNs measuring 7 to 200 nm in diameter drilled through a 20-nmthick SiNx membrane by focused ion milling. Both bulk and surface ionic currents in the nanopore are found to contribute to the flicker noise, with their respective contributions determined by salt concentration and pH in electrolytes as well as bias conditions. Increasing salt concentration at constant pH and voltage bias leads to increase in the bulk ionic current and noise therefrom. Changing pH at constant salt concentration and current bias results in variation of surface charge density, and hence alteration of surface ionic current and noise. In addition, the noise from Ag/AgCl electrodes can become predominant when the pore size is large and/or the salt concentration is high. Analysis of our comprehensive experimental results leads to the establishment of a generalized nanopore noise model. The model not only gives an excellent account of the experimental observations, but can also be used for evaluation of various noise components in much smaller nanopores currently not experimentally available.
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