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Room temperature ferromagnetism of Fe-doped ZnO and MgO thin films prepared by ink-jet printing
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
Faculty of Materials Science and Chemical Engineering, China University of Geosciences.
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2012 (English)In: MRS Proceedings, 2012Conference paper, 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.

Place, publisher, year, edition, pages
, MRS Proceedings, 1394
National Category
Condensed Matter Physics
URN: urn:nbn:se:kth:diva-102017DOI: 10.1557/opl.2012.824ScopusID: 2-s2.0-84879211954OAI: diva2:550339
2011 MRS Fall meeting

QC 70120906

Available from: 2012-09-06 Created: 2012-09-06 Last updated: 2012-09-07Bibliographically approved
In thesis
1. Properties of Multifunctional Oxide Thin Films Despostied by Ink-jet Printing
Open this publication in new window or tab >>Properties of Multifunctional Oxide Thin Films Despostied by Ink-jet Printing
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.
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
urn:nbn:se:kth:diva-102021 (URN)978-91-7501-477-7 (ISBN)
Public defence
2012-09-25, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)

QC 20120907

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

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