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Properties of Multifunctional Oxide Thin Films Despostied by Ink-jet Printing
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Ink-jet printing offers an ideal answer to the emerging trends and demands of depositing at ambient temperatures picoliter droplets of oxide solutions into functional thin films and device components with a high degree of pixel precision. It is a direct single-step mask-free patterning technique that enables multi-layer and 3D patterning. This method is fast, simple, easily scalable, precise, inexpensive and cost effective compared to any of other methods available for the realization of the promise of flexible, and/or stretchable electronics of the future on virtually any type of substrate. Because low temperatures are used and no aggressive chemicals are required for ink preparation, ink-jet technique is compatible with a very broad range of functional materials like polymers, proteins and even live cells, which can be used to fabricate inorganic/organic/bio hybrids, bio-sensors and lab-on-chip architectures. After a discussion of the essentials of ink-jet technology, this thesis focuses particularly on the art of designing long term stable inks for fabricating thin films and devices especially oxide functional components for electronics, solar energy conversion, opto-electronics and spintronics. We have investigated three classes of inks: nanoparticle suspension based, surface modified nanoparticles based, and direct precursor solution based. Examples of the films produced using these inks and their functional properties are:

1) In order to obtain magnetite nanoparticles with high magnetic moment and narrow size distribution in suspensions for medical diagnostics, we have developed a rapid mixing technique and produced nanoparticles with moments close to theoretical values (APL 2011 and Nanotechnology 2012). The suspensions produced have been tailored to be stable over a long period of time.

2)In order to design photonic band gaps, suspensions of spherical SiO2 particles were produced by chemical hydrolysis (JAP 2010 and JNP 2011 - not discussed in the thesis).

3) Using suspension inks, (ZnO)1-x(TiO2)x composite films have been printed and used to fabricate dye sensitized solar cells (JMR 2012). The thickness and the composition of the films can be easily tailored in the inkjet printing process. Consequently, the solar cell performance is optimized. We find that adding Ag nanoparticles improves the ‘metal-bridge’ between the TiO2 grains while maintaining the desired porous structure in the films. The photoluminescence spectra show that adding Ag reduces the emission intensity by a factor of two. This indicates that Ag atoms act as traps to capture electrons and inhibit recombination of electron-hole pairs, which is desirable for photo-voltaic applications.

4) To obtain and study room temperature contamination free ferromagnetic spintronic materials, defect induced and Fe doped MgO and ZnO were synthesized ‘in-situ’ by precursor solution technique (preprints). It is found that the origin of magnetism in these materials (APL 2012 and MRS 2012) is intrinsic and probably due to charge transfer hole doping.

5) ITO thin films were fabricated via inkjet printing directly from liquid precursors. The films are highly transparent (transparency >90% both in the visible and IR range, which is rather unique as compared to any other film growth technique) and conductive (resistivity can be ~0.03 Ω•cm). The films have nano-porous structure, which is an added bonus from ink jetting that makes such films applicable for a broad range of applications. One example is in implantable biomedical components and lab-on-chip architectures where high transparency of the well conductive ITO electrodes makes them easily compatible with the use of quantum dots and fluorescent dyes.

In summary, the inkjet patterning technique is incredibly versatile and applicable for a multitude of metal and oxide deposition and patterning. Especially in the case of using acetate solutions as inks (a method demonstrated for the first time by our group), the oxide films can be prepared ‘in-situ’ by direct patterning on the substrate without any prior synthesis stages, and the fabricated films are stoichiometric, uniform and smooth. This technique will most certainly continue to be a versatile tool in industrial manufacturing processes for material deposition in the future, as well as a unique fabrication tool for tailorable functional components and devices.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , x, 98 p.
Keyword [en]
ink-jet printing, oixde, thin film, ink, suspension, dye sensitized solar cell, functional properties, magnetism, diluted magnetic semiconductors
National Category
Condensed Matter Physics Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-102021ISBN: 978-91-7501-477-7 (print)OAI: oai:DiVA.org:kth-102021DiVA: diva2:550350
Public defence
2012-09-25, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Vinnova
Note

QC 20120907

Available from: 2012-09-07 Created: 2012-09-06 Last updated: 2012-09-07Bibliographically approved
List of papers
1. The art of tailoring inks for inkjet printing metal oxides
Open this publication in new window or tab >>The art of tailoring inks for inkjet printing metal oxides
2012 (English)Manuscript (preprint) (Other academic)
Abstract [en]

Inkjet printing has become a promising, efficient, inexpensive, scalable technique for materials deposition and mask-less patterning in many device applications. This article provides an introduction of the essentials of inkjet printing technology and ink preparation which remains a challenge especially for printing oxide transparent materials. After introducing the essentials of an inkjet printer and the process of the conversion of liquid ink into solid thin films of oxide materials, we present two approaches to the tailoring of inks, especially relevant for piezoelectric drop-on-demand ink jet printer: (1) the inks prepared from oxide particle suspensions (e.g., SiO2, TiO2, Fe3O4), and (2) metal-acetates precursor solutions for direct printing of thin films subsequently processed by calcination into the respective oxides like undoped and doped ZnO, MgO, ITO among others. The oxide films prepared this way using high purity precursors are free from undesirable contaminations, stoichiometric and when annealed appropriately produce smooth printed thin films. We place special emphasis upon preparation of inks that are stable without sediments over time so that the printing process is reliable and repeatable, and the obtained oxide films are dense and uniform. Also, for some of the inks containing multi-type acetates with possible phase separation even before calcinations we have developed a chelating procedure in order to tailor the films into single phase homogeneity. The films are characterized by optical microscope for micro features, high resolution SEM in a Nova600-Nanolab SEM/FIB system, and JEOL atomic force microscope for their morphology.

Publisher
116 p.
Keyword
Ink-jet printing, oxide thin films, inks
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-102007 (URN)978-91-7501-477-7 (ISBN)
Funder
Vinnova
Note

QS 2012

Available from: 2012-09-06 Created: 2012-09-06 Last updated: 2013-06-12Bibliographically approved
2. Inkjet-printed (ZnO)1-x(TiO2)x composite films for solar cell applications
Open this publication in new window or tab >>Inkjet-printed (ZnO)1-x(TiO2)x composite films for solar cell applications
Show others...
(English)In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326Article in journal, Editorial material (Refereed) Accepted
Keyword
Ink-jet printing, composite film, photovoltaic
National Category
Composite Science and Engineering
Identifiers
urn:nbn:se:kth:diva-102009 (URN)
Note

QS 2012

Available from: 2012-09-06 Created: 2012-09-06 Last updated: 2017-12-07Bibliographically approved
3. Thermal anealing effects on Ag/TiO2 thin films prepared by ink-jet printing
Open this publication in new window or tab >>Thermal anealing effects on Ag/TiO2 thin films prepared by ink-jet printing
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The effects of heat treatment on both the phase structure and the electronic band structure were studied for Ag/TiO2 composite films prepared by inkjet printing. Ag nanoparticles can form ‘metal-bridge’ to link TiO2 particles in the mesoporous structured films and improve the transport properties of the films. The distribution of Ag in the composite films shows dependence on the annealing conditions: Ag clusters were observed at high annealing temperature (>600 °C), and they can be annihilated by a longer time annealing. Comparing with pure TiO2 films, the decreased intensity of the photoluminescence (PL) emission spectra of Ag/TiO2 composite films indicates that the doped Ag atoms could act as traps to capture electron and inhabit the recombination of electron-hole pairs. From the identifiable PL emission peaks, the band structure of the films is deduced.

Keyword
Ink-jet printing, annealing, microstructure, photoluminescence
National Category
Composite Science and Engineering
Identifiers
urn:nbn:se:kth:diva-102012 (URN)
Funder
Vinnova
Note

QS 2012

Available from: 2012-09-06 Created: 2012-09-06 Last updated: 2012-09-07Bibliographically approved
4. Rapid mixing: A route to synthesize magnetite nanoparticles with high moment
Open this publication in new window or tab >>Rapid mixing: A route to synthesize magnetite nanoparticles with high moment
Show others...
2011 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 99, no 22, 222501- p.Article in journal (Refereed) Published
Abstract [en]

We demonstrate the impact of rapid mixing of the precursors in a time scale of milliseconds on the reaction rate and magnetic properties of co-precipitated magnetite with a custom-made mixer. The mixed volume is directed into a desk-top AC susceptometer to monitor the magnetic response from the growing particles in real-time. These measurements indicate that the reaction is mostly completed within a minute. The obtained superparamagnetic nanoparticles exhibit a narrow size distribution and large magnetization (87 Am(2) kg(-1)). Transmission electron micrographs suggest that rapid mixing is the key for better crystallinity and a more uniform morphology leading to the observed magnetization values.

Keyword
iron compounds, magnetic moments, magnetic particles, magnetisation, mixing, nanofabrication, nanomagnetics, nanoparticles, paramagnetic materials, precipitation (physical chemistry), transmission electron microscopy
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-63270 (URN)10.1063/1.3662965 (DOI)000298244500044 ()2-s2.0-82955164407 (Scopus ID)
Note
QC 20120125Available from: 2012-01-25 Created: 2012-01-23 Last updated: 2017-12-08Bibliographically approved
5. Particle size and magnetic properties dependence on growth temperature for rapid mixed co-precipitated magnetite nanoparticles
Open this publication in new window or tab >>Particle size and magnetic properties dependence on growth temperature for rapid mixed co-precipitated magnetite nanoparticles
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2012 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, no 14, 145601- p.Article in journal (Refereed) Published
Abstract [en]

Magnetite nanoparticles have been prepared by co-precipitation using a custom-designed jet mixer to achieve rapid mixing (RM) of reactants in a timescale of milliseconds. The quick and stable nucleation obtained allows control of the particle size and size distribution via a more defined growth process. Nanoparticles of different sizes were prepared by controlling the processing temperature in the first few seconds post-mixing. The average size of the nanoparticles investigated using a Tecnai transmission electron microscope is found to increase with the temperature from 3.8 nm at 1 +/- 1 degrees C to 10.9 nm for particles grown at 95 +/- 1 degrees C. The temperature dependence of the size distribution follows the same trend and is explained in terms of Ostwald ripening of the magnetite nanoparticles during the co-precipitation of Fe2+ and Fe3+. The magnetic properties were studied by monitoring the blocking temperature via both DC and AC techniques. Strikingly, the obtained RM particles maintain the high magnetization (as high as similar to 88 A m(2) kg(-1) at 500 kA m(-1)) while the coercivity is as low as similar to 12 A m(-1) with the expected temperature dependence. Besides, by adding a drop of tetramethylammonium hydroxide, aqueous ferrofluids with long term stability are obtained, suggesting their suitability for applications in ferrofluid technology and biomedicine.

National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-93908 (URN)10.1088/0957-4484/23/14/145601 (DOI)000302140500007 ()2-s2.0-84858830697 (Scopus ID)
Funder
Vinnova
Note

QC 20120507

Available from: 2012-05-07 Created: 2012-05-03 Last updated: 2017-12-07Bibliographically approved
6. Room temperature ferromagnetism of Fe-doped ZnO and MgO thin films prepared by ink-jet printing
Open this publication in new window or tab >>Room temperature ferromagnetism of Fe-doped ZnO and MgO thin films prepared by ink-jet printing
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2012 (English)In: MRS Proceedings, 2012Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Room temperature magnetic properties of un-doped, as well as 10 at.% Fe-doped ZnOand MgO single-pass layer of ink-jet printed thin films have been investigated to obtain insightinto the role of the band gaps and mechanisms for the origin of ferromagnetic order in thesematerials. It is found that on doping with Fe, the saturation magnetization is enhanced by severalfoldin both systems when compared with the respective un-doped thin films. For a ~28 nm thickfilm of Fe-doped ZnO (Diluted Magnetic Semiconductor, DMS) we observe an enhancedmoment of 0.465 μB/Fe atom while it is around 0.111μB/Fe atom for the doped MgO (DilutedMagnetic Insulator, DMI) film of comparable thickness. Also, the pure ZnO is far moreferromagnetic than pure MgO at comparable low film thicknesses which can be attributed todefect induced magnetism originating from cat-ion vacancies. However, the film thicknessdependence of the magnetization and the defect concentrations are found to be significantlydifferent in the two systems so that a comparison of the magnetism becomes more complex forthicker films.

Series
MRS Proceedings, 1394
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-102017 (URN)10.1557/opl.2012.824 (DOI)2-s2.0-84879211954 (Scopus ID)
Conference
2011 MRS Fall meeting
Note

QC 70120906

Available from: 2012-09-06 Created: 2012-09-06 Last updated: 2012-09-07Bibliographically approved
7. Magnetic properties of inkjet printed Fe-doped ZnO thin films
Open this publication in new window or tab >>Magnetic properties of inkjet printed Fe-doped ZnO thin films
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Magnetic properties in semiconductors show dependences on the substance itself (the doped element and the matrix), the states (e.g., bulk, nanoparticles, or film) and the preparation methods, which attract huge interest for both functional applications and fundamental science. As a widespread used semiconductor, ZnO and Fe-doped ZnO thin films were prepared via calcination of the as-prepared acetates precursor films printed by inkjet technique. Their room temperature (RT) magnetic properties were investigated to obtain the insight into the origin of RT ferromagnetism (FM). It was found that the grain size of the films was reduced by Fe-doping. For ~30 nm thick films, the saturation magnetization (MS) of 10 at.% Fe-doped ZnO (3.8 emu/g) is 4 times higher than that of pure ZnO thin film (0.9 emu/g) prepared with the same route. We attribute the enhancement to: (i) the introduction of Fe atoms with unpaired 3d electrons which contribute to magnetism; and (ii) the Fe-doping increase the defect in the lattice structure of the ZnO matrix. The effects of calcination temperature on RTFM of 10 at.% Fe-doped thin films were studied, and the temperature dependent MS was observed. The RTFM depended on film thickness as well, which shows an initial increase and then decrease with the maximum MS of 4.44 emu/g obtained from the ~45 nm 10 at.% Fe-doped ZnO film. Possible reasons for the observed phenomena were discussed.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-102018 (URN)
Note

QS 2012

Available from: 2012-09-06 Created: 2012-09-06 Last updated: 2012-09-07Bibliographically approved
8. Magnetism of Fe-doped MgO thin films prepared by inkjet printing
Open this publication in new window or tab >>Magnetism of Fe-doped MgO thin films prepared by inkjet printing
(English)Manuscript (preprint) (Other academic)
Abstract [en]

We prepared MgO and Fe-doped MgO thin films by inkjet printing and investigated the room temperature ferromagnetism (RTFM) of the films. Films prepared from the same route show amorphous for pure MgO films while crystals for Fe-doped MgO thin films, indicating that the doped Fe atoms can improve the crystallinity of the films. The saturation magnetization of 10 at.% Fe-doped MgO film is ~5 times as much as that of pure MgO film with same thickness (~90 nm), implying the great enhancement of magnetism introduced by Fe-doping. The RTFM of 10 at.% Fe-doped MgO films shows dependence on calcination temperature and the film thickness, where the effects of defect and crystal structure on magnetism of films were discussed. From the L2,3-edge features, the coexistence of Fe2+ and Fe3+ cations in octahedral and tetrahedral sites of the crystals was deduced, which was consistent with the two lattice structures determined from X-ray diffraction. The unpaired 3d electrons in the lattices could interact with each other directly or mediated by anions/carriers, which contribute to the enhancement of RTFM in the Fe-doped films. The saturation magnetization of ~30 nm 10at.% Fe-doped MgO film was detected to be ~6.3 emu•cm-3 and the coercively was ~50 Oe.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-102019 (URN)
Note

QS 2012

Available from: 2012-09-06 Created: 2012-09-06 Last updated: 2012-09-07Bibliographically approved
9. Electronic structure of room-temperature ferromagnetic Mg1-xFexOy thin films
Open this publication in new window or tab >>Electronic structure of room-temperature ferromagnetic Mg1-xFexOy thin films
Show others...
2012 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 101, no 8, 082411- p.Article in journal (Refereed) Published
Abstract [en]

We present herein a soft x-ray spectroscopy study on the electronic and magnetic properties of Mg1-xFexOy thin films. A distinct shoulder feature on the absorption edge reflecting the unoccupied oxygen 2p states is evident in the intrinsic thin films, which diminishes upon Fe doping, while a pre-edge absorption feature (reflecting the O 2p-Fe 3d acceptor state) evolves with the same. Our findings demonstrate the reduction in the intrinsic holes as a result of charge-transfer hole doping. All the thin films display room-temperature ferromagnetism, and the saturation magnetization is found to increase from ca. 0.70 -> 4.34 emu/cm(3) on 7 at. % Fe doping.

Keyword
X-Ray-Absorption, Doped Zno, Oxides, Spectroscopy, Mgo
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-102020 (URN)10.1063/1.4747445 (DOI)000308420800062 ()2-s2.0-84865524887 (Scopus ID)
Funder
VinnovaSwedish Research Council
Note

QC 20120907

Available from: 2012-09-06 Created: 2012-09-06 Last updated: 2017-12-07Bibliographically approved

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