| 1. |
- Fang, Mej, et al.
(författare)
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'In-situ' preparation of metal oxide thin films by inkjet printing acetates solutions
- 2013
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Ingår i: Mater Res Soc Symp Proc. - : Springer Science and Business Media LLC. - 9781605115245 ; , s. 13-20
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Konferensbidrag (refereegranskat)abstract
- Direct printing of functional oxide thin films could provide a new route to low-cost, efficient and scalable fabrications of electronic devices. One challenge that remains open is to design the inks with long term stability for effective deposition of specific oxide materials of industrial importance. In this paper, we introduce a reliable method of producing stable inks for 'in-situ' deposition of oxide thin films by inkjet printing. The inks were prepared from metal-acetates solutions and printed on a variety of substrates. The acetate precursors were decomposed into oxide films during the subsequent calcination process to achieve the 'in-situ' deposition of the desired oxide films directly on the substrate. By this procedure we have obtained room temperature contamination free ferromagnetic spintronic materials like Fe doped MgO and ZnO films from their acetate(s) solutions. We find that the origin of magnetism in ZnO, MgO and their Fe-doped films to be intrinsic. For a 28 nm thick film of Fe-doped ZnO we observe an enhanced magnetic moment of 16.0 emu/cm3 while it is 5.5 emu/cm3 for the doped MgO film of single pass printed. The origin of magnetism is attributed to cat-ion vacancies. We have also fabricated highly transparent indium tin oxide films with a transparency >95% both in the visible and IR range which is rather unique compared to films grown by any other technique. The films have a nano-porous structure, an added bonus from inkjetting that makes such films advantageous for a broad range of applications.
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| 2. |
- Fang, Mei, 1984-, et al.
(författare)
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Room temperature ferromagnetism of Fe-doped ZnO and MgO thin films prepared by ink-jet printing
- 2012
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Ingår i: MRS Proceedings. - : Springer Science and Business Media LLC. - 0272-9172 .- 1946-4274.
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 3. |
- Reinhold, Ingo, 1981-, et al.
(författare)
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Analysis of Formation of an Individual Droplet Using a High-ResolutionMulti-Exposure Imaging System
- 2013
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Ingår i: International Conference on Digital Printing Technologies and Digital Fabrication. ; , s. 354-358
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Konferensbidrag (refereegranskat)abstract
- Localized dispensing of precious functional materials has attracted considerable interest in the academic as well as the industrial society. While the number of publications show numerous fields of applications in printed electronics, photovoltaics, display technologies and thin functional coatings, the transition into the industrial sector is often hindered by challenges resulting from ink-printhead combinations and their implications on reliability and stability of the process, as well as side-effects such as mist accumulation in heavy duty printing equipment.While measuring equipment to quantify various rheological and interfacial parameters foor fluid optimization has been developed with the accompanying mathematical models, the physical jetting experiment as well as high-duty printing trials cannot yet be substituted by these methods. In order to quantify the generation of a droplet alongside with its tailing behavior and mist formation as well as statistics based on cross-talk effects and relaxation-related effects, high-resolution and high-speed imaging are required.This paper examines the optical setup and outlines the required calculations for establishing sharp, high-resolution images using a combination of a high power laser diode with a resonant MEMS micro mirror with a theoretical resolution of 1.8 μm. The limitations of the setup regarding the achievable resolution as well as potential improvements are assessed. Furthermore, the experimental setup, including repetitive generation of nanosecond-pulses necessary for motion-blur-free images, will be discussed. Additionally, results from imaging a droplet formation process using a Xaar 126 printhead are discussed.
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| 4. |
- Reinhold, Ingo, et al.
(författare)
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Electrical through-hole and planar interconnect generation in roll-to-roll LED lighting manufacturing using industrial inkjet printheads
- 2011
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Ingår i: Mater Res Soc Symp Proc. - : Springer Science and Business Media LLC. - 9781618395399 ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- Despite the availability of many high-volume and low-cost manufacturing processes for LED-based lighting applications, relying mainly on fixed patterns such as LED-backlights and RGB-pixelated displays, novel applications, such as "mood lighting" or interior wall displays call for more complicated and shaped LED arrangements. The presented work is based of a novel roll-to-roll (R2R) process to adaptively and cost-efficiently generate LED arrangements on RMPD® substrates. Inkjet printing of planar and though-hole electrical interconnections is of high importance to the process, as it provides a fully digital way of interconnecting devices electrically, accounting for the actual position of the component and spatially provide different ink film thicknesses. Xaar's industrial inkjet printheads are used to dispense defined volumes of 50 pL of a silver nanoparticle ink in order to provide high reliability and good positioning accuracy while maintaining low satellite drop densities. Specific printing strategies are investigated at a print speed of 0.1 m/s to allow for a reliable electrical connection in case of up to 50 μm deep via connections to the buried component. Due to the low glass-transition nature of the underlying substrates, low sintering temperatures are required to preserve the mechanical properties of the substrate. Low temperature oven sintering yielding sufficient conductivity to drive a current of 40 mA will be discussed.
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| 5. |
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| 6. |
- Reinhold, Ingo, et al.
(författare)
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Inkjet Printing of Electrical Connections in Electronic Packaging
- 2011
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Ingår i: NIP27 : 27th International Conference on Digital Printing Technologies, October 2-6, 2011, Minneapolis, Minnesota ; Digital Fabrication 2011. - : The Society for Imaging Science and Technology. - 9780892082964 ; , s. 445-451
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Konferensbidrag (refereegranskat)abstract
- Two aspects were evaluated of an approach to produce inkjet printed electrical connections in a roll-to-roll application. In the first part it was demonstrated that inkjet printing with silver nanoparticles allows to connect LED dies embedded in a flexible polymeric substrate by way of electrical via connections and to operate the LED dies at their nominal 20 mA and 3 V driving conditions. A standard convection oven process was used to sinter the inkjet printed tracks. The second part of the work focused on identifying sinter technologies that provide the required fast processing times needed for roll-to-roll applications. IR irradiation, Rapid Electrical Sintering, and Broadband Photonic Curing were evaluated and compared with Convective Oven Sintering as benchmark technique. All these techniques produced similar track conductivities. Fastest operation was obtained with Broadband Photonic Curing, which enabled a total process time of three seconds as compared with 150°C and 30 min in the convection oven.
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| 7. |
- Reinhold, Ingo, et al.
(författare)
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Inkjet printing of electrical vias
- 2011
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Ingår i: EMPC - Eur. Microelectron. Packag. Conf., Proc.. - 9780956808608
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Konferensbidrag (refereegranskat)abstract
- Inkjet printing of planar and via (through-hole) electrical interconnections is developed to be incorporated into a roll-to-roll manufacturing line. The specific roll-to-roll machine uses rotary RMPD® technology, self-alignment of bare LED dies, and inkjet printing of the electrical connections to the LEDs dies. The key problem to be solved is the inkjet printing of electrical connections through via holes with vertical walls Xaar126-50pL industrial inkjet printheads were used to print silver nano particle ink at 0.1 m/s to connect through LED vias of 90 μm diameter and up to 50 μm depth. While high throughput sintering techniques are desirable for the specific roll-to-roll machine standard convection oven sintering was applied for the proof of principle described here. Sintering at temperatures as low as 135 °C for 30 min prevented damage to the substrate and LED dies and yielded electrical connections that allowed to drive LEDs with 20 mA at 3V under emission of bright green light.
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| 8. |
- Reinhold, Ingo, et al.
(författare)
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Inkjet printing of isolation layers for back-contacted silicon- heterojunction solar cells
- 2011
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Ingår i: NIP27 : 27th International Conference on Digital Printing Technologies, October 2-6, 2011, Minneapolis, Minnesota ; Digital Fabrication 2011. - : The Society for Imaging Science and Technology. - 9780892082964 ; , s. 651-654
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Konferensbidrag (refereegranskat)abstract
- For wafer based silicon solar cells, the combination of amorphous/crystalline silicon (a-Si:H/c-Si) heterojunction emitters (SHJ) [1] and back-contacted back-junction solar cell concepts (BCBJ) [2] offer a very high efficiency potential of around 24%. Stangl et al. proposed a relatively simple and therefore attractive cell concept comprising a two level metallization isolated by an insulation layer. The emitter layer consisting of doped amorphous silicon with a thickness of several nm and the emitter metallization layer comprise circular openings where the back surface field layers and the respective metallization establish contact to the absorber. In this work the potential of inkjet printing for the deposition of the isolation layer with photoresists or other polymeric fluids is evaluated. Challenges are the required placement precision and the feature size. In order to produce circular openings of the order 10 μm, the drop formation has to be optimized, and the ink spreading on both surfaces - on the aluminum emitter and on the silicon wafer substrate - have to be controlled.
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| 9. |
- Reinhold, Ingo, et al.
(författare)
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Spectrally Enhanced Photonic Sintering
- 2012
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Ingår i: NIP28 : 28th international conference on digital printing technologies : technical program and proceedings. - : The Society for Imaging Science and Technology. - 9780892083022 ; , s. 424-430
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Konferensbidrag (refereegranskat)abstract
- Inkjet printing with silver nanoparticle inks is frequently being used to print electrically conductive structures. However, typically slow thermal post-processes are applied to produce metallic contact between the nanoparticles resulting in the high electrical conductivity. In an earlier evaluation a number of different post-process were investigated for their capability to sinter the inkjet printed structures within such short time frame to allow for integration into roll-to-roll or roll-to-sheet machines. Among the different techniques like IR-irradiation, and Rapid Electrical Sintering, Photonic Sintering appeared as the most prominent candidate, and was shown to enable electrical conductivities equal to oven sintering. In that previous investigation the inkjet printed structures were dried and subsequently shipped for off-line post treatment. The hybrid process of inkjet printing of silver nanoparticle inks and photonic sintering was further investigated with the goal to implement both processes on a roll-to-roll machine. Specifically it was attempted to perform the photonic sintering process with a single lamp and without an intermediate drying process. In this paper we investigate the sintering characteristics of an inkjet printed, wet deposit having liquid volumes of 510 pL per 100 μm2 on non-absorbing substrates using a single Xenon Sintering 2000 system. The paper specifically highlights the importance of radiation homogeneity, threshold energy, substrate and track morphology onto the sintering process. The influence of the spectral composition of the light is analyzed. The findings allow for spectral tailoring of the process to successfully work on PI and PET irrespective of the illumination source.
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| 10. |
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