Browsing by Author "Ramon, Eloi"
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- All-inkjet printed organic transistors: Dielectric surface passivation techniques for improved operational stability and lifetimePublication . Gomes, Henrique L.; Medeiros, M. C. R.; Villani, F.; Canudo, J. M.; Loffredo, F.; Miscioscia, R.; Martinez-Domingo, Carme; Ramon, Eloi; Sowade, Enrico; Mitra, K. Y.We report about the use of a printed pentafluorothiophenol layer on top of the dielectric surface as a passivation coating to improve the operational stability of all-ink-jet printed transistors. Transistors with bottom-gate structure were fabricated using cross-linked poly-4-vinylphenol (c-PVP) as dielectric layer and an ink formulation of an amorphous triarylamine polymer as semiconductor. The resulting TFTs had low turn-on voltage (Vth < |5 V|) and a mobility ≈0.1 cm2/(V s). A comparison of identically fabricated transistors shows that devices with coated dielectric have a higher operational stability than those using bare c-PVP. This conclusion is supported by a quantitative study of the threshold voltage shift with time under continuous operation. Long exposure to the ambient atmosphere causes an increase in the threshold voltage strongly dependent on the used semiconducting ink formulation.
- All-inkjet-printed thin-film transistors: manufacturing process reliability by root cause analysisPublication . Sowade, Enrico; Ramon, Eloi; Mitra, Kalyan Yoti; Martinez-Domingo, Carme; Pedro, Marta; Pallares, Jofre; Loffredo, Fausta; Villani, Fulvia; Gomes, Henrique L.; Teres, Lluis; Baumann, Reinhard R.We report on the detailed electrical investigation of all-inkjet-printed thin-film transistor (TFT) arrays focusing on TFT failures and their origins. The TFT arrays were manufactured on flexible polymer substrates in ambient condition without the need for cleanroom environment or inert atmosphere and at a maximum temperature of 150 degrees C. Alternative manufacturing processes for electronic devices such as inkjet printing suffer from lower accuracy compared to traditional microelectronic manufacturing methods. Furthermore, usually printing methods do not allow the manufacturing of electronic devices with high yield (high number of functional devices). In general, the manufacturing yield is much lower compared to the established conventional manufacturing methods based on lithography. Thus, the focus of this contribution is set on a comprehensive analysis of defective TFTs printed by inkjet technology. Based on root cause analysis, we present the defects by developing failure categories and discuss the reasons for the defects. This procedure identifies failure origins and allows the optimization of the manufacturing resulting finally to a yield improvement.
- Controlling the crack formation in inkjet-printed silver nanoparticle thin-films for high resolution patterning using intense pulsed light treatmentPublication . Gokhale, Pritesh; Mitra, Dana; Sowade, Enrico; Mitra, Kalyan Yoti; Gomes, Henrique L.; Ramon, Eloi; Al-Hamry, Ammar; Kanoun, Olfa; Baumann, Reinhard R.During the last years, intense pulsed light (IPL) processing has been employed and studied intensively for the drying and sintering of metal nanoparticle layers deposited by means of printing methods on flexible polymer substrates. IPL was found to be a very fast and substrate-gentle approach qualified for the field of flexible and large-area printed electronics, i.e. manufactured via roll-to-roll processing. In this contribution, IPL is used for the fine-patterning of printed silver nanoparticle layers. The patterning is obtained by induced and controlled crack formation in the thin silver layer due to the intense exposure of IPL. The crack formation is controlled by selection of the substrate material, the fine-tuning of the morphology of the silver layer and an application of a dielectric layer on top of the silver layer that acts as a stress concentrator. Careful optimization of the IPL parameters allowed to adjust the lateral width of the crack. This novel approach turned out to be a fast and reproducible high-resolution patterning process for multiple applications, e.g. to pattern the source-drain electrodes for all-inkjet-printed thin-film transistors.
- Inkjet printed metal insulator semiconductor (MIS) diodes for organic and flexible electronic applicationPublication . Mitra, Kalyan Yoti; Sternkiker, Christoph; Martinez-Domingo, Carme; Sowade, Enrico; Ramon, Eloi; Carrabina, Jordi; Gomes, Henrique L.; Baumann, Reinhard R.All inkjet printed rectifying diodes based on a metal-insulator-semiconductor (MIS) layer stack are presented. The rectifying properties were optimized by careful selection of the insulator interlayer thickness and the layout structure. The different diode architectures based on the following materials are investigated: (1) silver/ poly (methylmethacrylate-methacrylic acid)/ polytriarylamine/ silver, (2) silver/ polytriarylamine/ poly (methylmethacrylate-methacrylic acid)/ silver, and (3) silver/ poly (methylmethacrylate-methacrylic acid)/ poly-triarylamine/ poly(3,4-ethylenedioxythiophene) poly (styrenesulfonate). The MIS diodes show an averaged rectification ratio of 200 and reasonable forward current density reaching 40 mA cm -2. They are suitable for a number of applications in flexible printed organic electronics.
- Potential up-scaling of inkjet-printed devices for logical circuits in flexible electronicsPublication . Mitra, Kalyan Yoti; Sowade, Enrico; Martinez-Domingo, Carme; Ramon, Eloi; Carrabina, Jordi; Gomes, Henrique L.; Baumann, Reinhard R.; Logothetidis, S.; Laskarakis, A.; Gravalidis, C.Inkjet Technology is often mis-believed to be a deposition/patterning technology which is not meant for high fabrication throughput in the field of printed and flexible electronics. In this work, we report on the 1) printing, 2) fabrication yield and 3) characterization of exemplary simple devices e.g. capacitors, organic transistors etc. which are the basic building blocks for logical circuits. For this purpose, printing is performed first with a Proof of concept Inkjet printing system Dimatix Material Printer 2831 (DMP 2831) using 10 pL small print-heads and then with Dimatix Material Printer 3000 (DMP 3000) using 35 pL industrial print-heads (from Fujifilm Dimatix). Printing at DMP 3000 using industrial print-heads (in Sheet-to-sheet) paves the path towards industrialization which can be defined by printing in Roll-to-Roll format using industrial print-heads. This pavement can be termed as "Bridging Platform". This transfer to "Bridging Platform" from 10 pL small print-heads to 35 pL industrial print-heads help the inkjet-printed devices to evolve on the basis of functionality and also in form of up-scaled quantities. The high printed quantities and yield of inkjet-printed devices justify the deposition reliability and potential to print circuits. This reliability is very much desired when it comes to printing of circuits e.g. inverters, ring oscillator and any other planned complex logical circuits which require devices e.g. organic transistors which needs to get connected in different staged levels. Also, the up-scaled inkjet-printed devices are characterized and they reflect a domain under which they can work to their optimal status. This status is much wanted for predicting the real device functionality and integration of them into a planned circuit.
- Up-scaling of the manufacturing of all-inkjet-printed organic thin-film transistors: device performance and manufacturing yield of transistor arraysPublication . Sowade, Enrico; Mitra, Kalyan Yoti; Ramon, Eloi; Martinez-Domingo, Carme; Villani, Fulvia; Loffredo, Fausta; Gomes, Henrique L.; Baumann, Reinhard R.All-inkjet-printed thin-film transistors (TFTs) have been demonstrated in literature using mainly laboratory inkjet equipment, simple one-channel layout and only a low number of manufactured TFT devices. We report on the development and the up-scaling of the manufacturing of all-inkjet-printed TFT arrays using industrial inkjet equipment. The manufacturing of the TFTs was carried out in ambient condition without the need for cleanroom environments or inert atmospheres and at a maximum temperature of 150 degrees C enabling the use of flexible polymer films as substrate. Arrays of 924 TFTs were manufactured on an area of about DIN A4 (297 x 420 mm(2)). This allows the consideration of statistics, e.g. to determine the process yield as a function of device design and layout. We present process yields for all-inkjet-printed TTFs up to 82% demonstrating the potential of the developed all-inkjet-printing process. (C) 2015 Elsevier B.V. All rights reserved.