| 1. |
- 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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| 2. |
- Kukli, Kaupo, et al.
(författare)
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Holmium and titanium oxide nanolaminates by atomic layer deposition
- 2014
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Ingår i: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 565, s. 165-171
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Tidskriftsartikel (refereegranskat)abstract
- Nanolaminate (nanomultilayer) thin films of TiO2 and Ho2O3 were grown on Si(001) substrates by atomic layer deposition at 300 degrees C from alkoxide and beta-diketonate based metal precursors and ozone. Individual layer thicknesses were 2 nm for TiO2 and 4.5 nm for Ho2O3. As-deposited films were smooth and X-ray amorphous. After annealing at 800 degrees C and higher temperatures the nanolaminate structure was destroyed by solid-state reaction to form Ho2Ti2O7. The films demonstrated diamagnetic or paramagnetic behaviour in the as-deposited state. After annealing, the films possessed net magnetic moment, allowing one to record saturation magnetization and weak coercivity.
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| 3. |
- Niinisto, Jaakko, et al.
(författare)
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Advanced cyclopentadienyl precursors for atomic layer deposition of ZrO2 thin films
- 2008
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 18:28, s. 3385-3390
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Tidskriftsartikel (refereegranskat)abstract
- ZrO2 thin films were grown onto silicon (100) substrates by atomic layer deposition (ALD) using novel cyclopentadienyl-type precursors, namely (CpMe)(2)ZrMe2 and (CpMe)(2)Zr(OMe) Me (Cp = cyclopentadienyl, C5H5) together with ozone as the oxygen source. Growth characteristics were studied in the temperature range of 250 to 500 degrees C. An ALD-type self-limiting growth mode was verified for both processes at 350 degrees C where highly conformal films were deposited onto high aspect ratio trenches. Signs of thermal decomposition were not observed at or below 400 degrees C, a temperature considerably exceeding the thermal decomposition temperature of the Zr-alkylamides. Processing parameters were optimised at 350 degrees C, where deposition rates of 0.55 and 0.65 angstrom cycle(-1) were obtained for (CpMe)(2)ZrMe2/O-3 and (CpMe)(2)Zr(OMe)Me/O-3, respectively. The films grown from both precursors were stoichiometric and polycrystalline with an increasing contribution from the metastable cubic phase with decreasing film thickness. In the films grown from (CpMe)(2)ZrMe2, the breakdown field did not essentially depend on the film thickness, whereas in the films grown from (CpMe)(2)Zr(OMe)Me the structural homogeneity and breakdown field increased with decreasing film thickness. The films exhibited good capacitive properties that were characteristic of insulating oxides and did not essentially depend on the precursor chemistry.
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| 4. |
- Tamm, Aile, et al.
(författare)
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Atomic layer deposition of high-k dielectrics on carbon nanoparticles
- 2013
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Ingår i: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 538, s. 16-20
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Tidskriftsartikel (refereegranskat)abstract
- Carbon nanoparticles were synthesized from 5-methylresorcinol and formaldehyde via base catalysed polycondensation reaction and distributed over silicon oxide wafers and aluminium oxide thin films. These particles essentially possessed monocrystalline graphite structure. The particles were covered by hafnium oxide thin films in metal chloride based atomic layer deposition process carried out at 300 degrees C. Upon deposition of HfO2, thin crystalline metal oxide layer containing mostly cubic phase was formed. At the same time, deposition of the metal oxide caused reduction of the sizes of graphite particles and essential increase in the disorder in carbon.
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| 5. |
- Tamm, Aile, et al.
(författare)
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Atomic layer deposition of ZrO2 for graphene-based multilayer structures: In situ and ex situ characterization of growth process
- 2014
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Ingår i: Physica Status Solidi (a) applications and materials science. - : Wiley-VCH Verlag. - 1862-6300 .- 1862-6319. ; 211:2, s. 397-402
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Tidskriftsartikel (refereegranskat)abstract
- Real time monitoring of atomic layer deposition by quartz crystal microbalance (QCM) was used to follow the growth of ZrO2 thin films on graphene. The films were grown from ZrCl4 and H2O on graphene prepared by chemical vapor deposition method on 100-nm thick nickel film or on Cu-foil and transferred onto QCM sensor. The deposition was performed at a substrate temperature of 190 degrees C. The growth of the dielectric film on graphene was significantly retarded compared to the process carried out on QCM without graphene. After the deposition of dielectric films, the basic structure of graphene was retained.
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