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Branquinho, Rita, Daniela Salgueiro, Lidia Santos, Pedro Barquinha, Luis Pereira, Rodrigo Martins, and Elvira Fortunato. "{Aqueous Combustion Synthesis of Aluminum Oxide Thin Films and Application as Gate Dielectric in GZTO Solution-Based TFTs}." {ACS APPLIED MATERIALS & INTERFACES}. {6} (Submitted): {19592-19599}. Abstract

{Solution processing has been recently considered as an option when trying to reduce the costs associated with deposition under vacuum. In this context, most of the research efforts have been centered in the development of the semiconductors processes nevertheless the development of the most suitable dielectrics for oxide based transistors is as relevant as the semiconductor layer itself. In this work we explore the solution combustion synthesis and report on a completely new and green route for the preparation of amorphous aluminum oxide thin films; introducing water as solvent. Optimized dielectric layers were obtained for a water based precursor solution with 0.1 M concentration and demonstrated high capacitance, 625 nF cm(-2) at 10 kHz, and a permittivity of 7.1. These thin films were successfully applied as gate dielectric in solution processed gallium-zinc-tin oxide (GZTO) thin film transistors (TFTs) yielding good electrical performance such as subthreshold slope of about 0.3 V dec(-1) and mobility above 1.3 cm(2) V-1 s(-1).}

Santos, Lidia, Joana P. Neto, Ana Crespo, Daniela Nunes, Nuno Costa, Isabel M. Fonseca, Pedro Barquinha, Luis Pereira, Jorge Silva, Rodrigo Martins, and Elvira Fortunato. "{WO3 Nanoparticle-Based Conformable pH Sensor}." {ACS APPLIED MATERIALS & INTERFACES}. {6} (Submitted): {12226-12234}. Abstract

{pH is a vital physiological parameter that can be used for disease diagnosis and treatment as well as in monitoring other biological processes. Metal/metal oxide based pH sensors have several advantages regarding their reliability, miniaturization, and cost-effectiveness, which are critical characteristics for in vivo applications. In this work, WO3 nanoparticles were electrodeposited on flexible substrates over metal electrodes with a sensing area of 1 mm(2). These sensors show a sensitivity of -56.7 +/- 1.3 mV/pH, in a wide pH range of 9 to 5. A proof of concept is also demonstrated using a flexible reference electrode in solid electrolyte with a curved surface. A good balance between the performance parameters (sensitivity), the production costs, and simplicity of the sensors was accomplished, as required for wearable biomedical devices.}

Zanarini, Simone, Nadia Garino, Jijeesh Ravi Nair, Carlotta Francia, Pawel Jerzy Wojcik, Luis Pereira, Elvira Fortunato, Rodrigo Martins, Silvia Bodoardo, and Nerino Penazzi. "{Contrast Enhancement in Polymeric Electrochromic Devices Encompassing Room Temperature Ionic Liquids}." {INTERNATIONAL JOURNAL OF ELECTROCHEMICAL SCIENCE}. {9} (Submitted): {1650-1662}. Abstract

{We report the preparation and spectro-electrochemical characterization of electrochromic devices (ECD) combining inkjet-printed WO3 as cathode and electro-deposited V2O5 as anode. ECD were prepared for the first time with an optimized formulation of gel polymer electrolyte based on Bisphenol A ethoxylate dimethacrylate and Poly(ethylene glycol) methyl ether methacrylate (BEMA/PEGMA) encompassing the Room Temperature Ionic Liquid (RTIL, 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) as solvent. The UV-VIS spectrum of ECD was recorded at different potentials during Li+ insertion and de-insertion; additionally the Percent Trasmittance (T%) of ECD vs. time was investigated during repeated bleaching and coloring cycles allowing thus the estimation of switching times and device stability. Due to the lower ionic conductivity and the apparent superior solvent permeability within WO3 active layer, RTIL containing ECD showed slower switching times, but higher contrast with respect to the similar ones with EC/DEC as solvent. These results indicate that the ECD containing environment-friendly RTIL electrolytes are suitable for applications requiring high contrast, high safety and moderately fast switching times.}

Schmeisser, Dieter, Joerg Haeberle, Pedro Barquinha, Diana Gaspar, Luis Pereira, Rodrigo Martins, and Elvira Fortunato. "{Electronic structure of amorphous ZnO films}." {PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 11, NO 9-10}. Eds. M. {Godlewski, and A. } Zakrzewski. Vol. {11}. {Physica Status Solidi C-Current Topics in Solid State Physics}, {11}. Submitted. {1476-1480}. Abstract

{We use resonant photoemission spectroscopy (resPES) to study the electronic properties of amorphous ZnO (a-ZnO) layers. We report on the core levels, the valence band (VB) PES data, and the X-ray absorption (XAS) data which we use for the conduction band (CB) density of states. From these results we are able to derive the partial density of states (pDOS) of O2p and Zn4s4p states in the VB and CB, respectively as well as a band scheme. At the O1s resonance we observe a band of localized defect states which is located between the Fermi energy and the CBM. At the Zn2p edge the XAS data indicate that localized Zn4s4p states are involved in the DOS starting already at the Fermi energy. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim}

Gaspar, D., S. N. Fernandes, G. dea Oliveira, J. G. Fernandes, P. Grey, R. V. Pontes, L. Pereira, R. Martins, M. H. Godinho, and E. Fortunato. "{Nanocrystalline cellulose applied simultaneously as the gate dielectric and the substrate in flexible field effect transistors.}." Nanotechnology. 25 (2014): 094008. AbstractWebsite

Cotton-based nanocrystalline cellulose (NCC), also known as nanopaper, one of the major sources of renewable materials, is a promising substrate and component for producing low cost fully recyclable flexible paper electronic devices and systems due to its properties (lightweight, stiffness, non-toxicity, transparency, low thermal expansion, gas impermeability and improved mechanical properties).Here, we have demonstrated for the first time a thin transparent nanopaper-based field effect transistor (FET) where NCC is simultaneously used as the substrate and as the gate dielectric layer in an 'interstrate' structure, since the device is built on both sides of the NCC films; while the active channel layer is based on oxide amorphous semiconductors, the gate electrode is based on a transparent conductive oxide.Such hybrid FETs present excellent operating characteristics such as high channel saturation mobility (>7 cm(2) V (-1) s(-1)), drain-source current on/off modulation ratio higher than 10(5), enhancement n-type operation and subthreshold gate voltage swing of 2.11 V/decade. The NCC film FET characteristics have been measured in air ambient conditions and present good stability, after two weeks of being processed, without any type of encapsulation or passivation layer. The results obtained are comparable to ones produced for conventional cellulose paper, marking this out as a promising approach for attaining high-performance disposable electronics such as paper displays, smart labels, smart packaging, RFID (radio-frequency identification) and point-of-care systems for self-analysis in bioscience applications, among others.

Pereira, Sónia, Alexandra Gonçalves, Nuno Correia, Joana Pinto, Lu\'ıs Pereira, Rodrigo Martins, and Elvira Fortunato. "{Electrochromic behavior of NiO thin films deposited by e-beam evaporation at room temperature}." Solar Energy Materials and Solar Cells. 120 (2014): 109-115. AbstractWebsite
Wojcik, Pawel Jerzy, Rodrigo Martins, and Elvira Fortunato. "{Statistical Mixture Design and Multivariate Analysis of Inkjet Printed a ‑ WO 3 /TiO 2 /WO}." (2014). Abstract
Pereira, L., D. Gaspar, D. Guerin, a Delattre, E. Fortunato, and R. Martins. "{The influence of fibril composition and dimension on the performance of paper gated oxide transistors.}." Nanotechnology. 25 (2014): 094007. AbstractWebsite

Paper electronics is a topic of great interest due the possibility of having low-cost, disposable and recyclable electronic devices. The final goal is to make paper itself an active part of such devices. In this work we present new approaches in the selection of tailored paper, aiming to use it simultaneously as substrate and dielectric in oxide based paper field effect transistors (FETs). From the work performed, it was observed that the gate leakage current in paper FETs can be reduced using a dense microfiber/nanofiber cellulose paper as the dielectric. Also, the stability of these devices against changes in relative humidity is improved. On other hand, if the pH of the microfiber/nanofiber cellulose pulp is modified by the addition of HCl, the saturation mobility of the devices increases up to 16 cm(2) V(-1) s(-1), with an ION/IOFF ratio close to 10(5).

Nandy, Suman, Gonçalo Gonçalves, Joana Vaz Pinto, Tito Busani, Vitor Figueiredo, Lu\'ıs Pereira, Rodrigo Ferrão {Paiva Martins}, and Elvira Fortunato. "{Current transport mechanism at metal-semiconductor nanoscale interfaces based on ultrahigh density arrays of p-type NiO nano-pillars.}." Nanoscale. 5 (2013): 11699-709. AbstractWebsite

The present work focuses on a qualitative analysis of localised I-V characteristics based on the nanostructure morphology of highly dense arrays of p-type NiO nano-pillars (NiO-NPs). Vertically aligned NiO-NPs have been grown on different substrates by using a glancing angle deposition (GLAD) technique. The preferred orientation of as grown NiO-NPs was controlled by the deposition pressure. The NiO-NPs displayed a polar surface with a microscopic dipole moment along the (111) plane (Tasker's type III). Consequently, the crystal plane dependent surface electron accumulation layer and the lattice disorder at the grain boundary interface showed a non-uniform current distribution throughout the sample surface, demonstrated by a conducting AFM technique (c-AFM). The variation in I-V for different points in a single current distribution grain (CD-grain) has been attributed to the variation of Schottky barrier height (SBH) at the metal-semiconductor (M-S) interface. Furthermore, we observed that the strain produced during the NiO-NPs growth can modulate the SBH. Inbound strain acts as an external field to influence the local electric field at the M-S interface causing a variation in SBH with the NPs orientation. This paper shows that vertical arrays of NiO-NPs are potential candidates for nanoscale devices because they have a great impact on the local current transport mechanism due to its nanostructure morphology.

Alves, Raquel D., Lu\'ısa C. Rodrigues, Juliana R. Andrade, Mariana Fernandes, Joana V. Pinto, Lu\'ıs Pereira, Agnieszka Pawlicka, Rodrigo Martins, Elvira Fortunato, Verónica {de Zea Bermudez}, and Maria Manuela Silva. "{Gelatin n Zn(CF 3 SO 3 ) 2 Polymer Electrolytes for Electrochromic Devices}." Electroanalysis. 25 (2013): 1483-1490. AbstractWebsite
Parthiban, Shanmugam, Elamurugu Elangovan, Pradipta K. Nayak, Alexandra Gonçalves, Daniela Nunes, Lu\'ıs Pereira, Pedro Barquinha, Tito Busani, Elvira Fortunato, and Rodrigo Martins. "{Performances of Microcrystalline Zinc Tin Oxide Thin-Film Transistors Processed by Spray Pyrolysis}." 9 (2013): 825-831. Abstract
Branquinho, Rita, Joana V. Pinto, Tito Busani, Pedro Barquinha, Luis Pereira, Pedro Viana Baptista, Rodrigo Martins, and Elvira Fortunato. "{Plastic Compatible Sputtered Ta O Sensitive Layer for Oxide Semiconductor TFT Sensors}." 9 (2013): 723-728. Abstract
a.M. Ramos, S. Pereira, M. T. Cidade, G. Pereira, R. Branquinho, L. Pereira, R. Martins, and E. Fortunato. "{Preparation and characterization of cellulose nanocomposite hydrogels as functional electrolytes}." Solid State Ionics. 242 (2013): 26-32. AbstractWebsite
Alves, R. D., L. C. Rodrigues, J. R. Andrade, A. Pawlicka, L. Pereira, R. Martins, E. Fortunato, and M. M. Silva. "{Study and Characterization of a Novel Polymer Electrolyte Based on Agar Doped with Magnesium Triflate}." Molecular Crystals and Liquid Crystals. 570 (2013): 1-11. AbstractWebsite
Pereira, Lu\'ıs, Pedro Barquinha, Gonçalo Gonçalves, Elvira Fortunato, and Rodrigo Martins. "{Multicomponent dielectrics for oxide TFT}." Eds. Ferechteh H. Teherani, David C. Look, and David J. Rogers. Vol. 8263. 2012. 826316–16. Abstract
Martins, R., V. Figueiredo, R. Barros, P. Barquinha, G. Gonçalves, L. Pereira, I. Ferreira, and E. Fortunato. "{P-type oxide-based thin film transistors produced at low temperatures}." Eds. Ferechteh H. Teherani, David C. Look, and David J. Rogers. Vol. 8263. 2012. 826315–15. Abstract
Baquinha, Pedro, Rodrigo Martins, Luis Pereira, and Elvira Fortunato Transparent Oxide Electronics. Wiley, 2012.
Wojcik, Pawel Jerzy, Ana Sofia Cruz, L\'ıdia Santos, Lu\'ıs Pereira, Rodrigo Martins, and Elvira Fortunato. "{Microstructure control of dual-phase inkjet-printed a-WO3/TiO2/WOX films for high-performance electrochromic applications}." Journal of Materials Chemistry. 22 (2012): 13268. AbstractWebsite
Martins, Rodrigo, Arokia Nathan, Raquel Barros, Lu\'ıs Pereira, Pedro Barquinha, Nuno Correia, Ricardo Costa, Arman Ahnood, Isabel Ferreira, and Elvira Fortunato. "{Complementary metal oxide semiconductor technology with and on paper.}." Advanced materials (Deerfield Beach, Fla.). 23 (2011): 4491-6. AbstractWebsite
Nolan, M. G., J. A. Hamilton, S. O’Brien, G. Bruno, L. Pereira, E. Fortunato, R. Martins, I. M. Povey, and M. E. Pemble. "{The characterisation of aerosol assisted CVD conducting, photocatalytic indium doped zinc oxide films}." Journal of Photochemistry and Photobiology A: Chemistry. 219 (2011): 10-15. AbstractWebsite
Martins, R., B. Brás, I. Ferreira, L. Pereira, P. Barquinha, N. Correia, R. Costa, T. Busani, A. Gonçalves, A. Pimentel, and E. Fortunato. "{Away from silicon era: the paper electronics}." Eds. Ferechteh H. Teherani, David C. Look, and David J. Rogers. Vol. 7940. 2011. 79400P–10. Abstract
O'Brien, Shane, Mehmet \c{C}opuroglu, Paul Tassie, Mark G. Nolan, Jeff A. Hamilton, Ian Povey, Luis Pereira, Rodrigo Martins, Elvira Fortunato, and Martyn E. Pemble. "{The effect of dopants on the morphology, microstructure and electrical properties of transparent zinc oxide films prepared by the sol-gel method}." Thin Solid Films. 520 (2011): 1174-1177. AbstractWebsite
Gonçalves, Gonçalo, Valentina Grasso, Pedro Barquinha, Lu\'ıs Pereira, Elangovan Elamurugu, Mauro Brignone, Rodrigo Martins, Vito Lambertini, and Elvira Fortunato. "{Role of Room Temperature Sputtered High Conductive and High Transparent Indium Zinc Oxide Film Contacts on the Performance of Orange, Green, and Blue Organic Light Emitting Diodes}." Plasma Processes and Polymers. 8 (2011): 340-345. AbstractWebsite
Martins, R. M. S., N. Schell, H. Reuther, L. Pereira, K. K. Mahesh, R. J. C. Silva, and Braz F. M. Fernandes. "{Texture development, microstructure and phase transformation characteristics of sputtered Ni–Ti Shape Memory Alloy films grown on TiN<111>}." Thin Solid Films. 519 (2010): 122-128. AbstractWebsite
O'Brien, Shane, Mark G. Nolan, Mehmet \c{C}opuroglu, Jeff A. Hamilton, Ian Povey, Luis Pereira, Rodrigo Martins, Elvira Fortunato, and Martyn Pemble. "{Zinc oxide thin films: Characterization and potential applications}." Thin Solid Films. 518 (2010): 4515-4519. AbstractWebsite